Lakhmir Singh Manjit Kaur Class 10 Chemistry 2nd Chapter “Acids Bases and Salts” solution

Lakhmir Singh Manjit Kaur Class 10 Chemistry 2nd Chapter “Acids Bases and Salts” solution

Lakhmir Singh and Manjit Kaur Chemistry solution: “Acids Bases and Salts” Chapter 2. Here you get easy solutions of Lakhmir Singh and Manjit Kaur Chemistry solution Chapter 2 . Here we have given Chapter 2 all solution of Class 10. Its help you to complete your homework.

  • Board – CBSE
  • Text Book – Chemistry
  • Class – 10
  • Chapter – 02

Lakhmir Singh Manjit Kaur Class 10 Chemistry 2nd Chapter Solution (1st Part)

Very short type questions

1) What colour do the fallowing indicator turn when added to a base and alkali (such as sodium hydroxide )?

Ans : a) methyl orange : the natural colour of methyl orange is orange

When it is added in alkali (NaOH) gives yellow colour of basic solution

Methyl orange indicated colour changes from orange to red.

b) litmus : the natural colour of litmus is purple. It is made into blue and red litmus for our Convenience.

When the red litmus paper is dipped in base (NaOH). It turns to blue

And blue litmus remains same in colour at base

Litmus show colour changes from red to blue

 c) red cabbage : red cabbage is natural indicator which have red in colour

When the red cabbage extract is added in base ( NaOH) it is change to blue colour solution of base

Red cabbage show colour changes from red to green

2) What colour do the fallowing indicator turn when added to an acid ( such as hydrochloric acid )?

Ans :

Litmus : blue colour litmus paper added in acid solution (HCl) it’s turns to red in colour.

Red litmus paper added in acid solution it’s remains same.

Litmus show colour changes from blue to red

Methyl orange : When methyl orange added in acid (HCl) gives red colour of acid solution

Methyl orange show colour changes from orange to red.

3) Name the indicator which is red in acid solution but turns blue in basic solution

Ans –  litmus .

Litmus show red colour in acid solution and blue colour in basic solution

4) Name an indicator which is pink in alkaline solution but turns colourless in acidic solution ?

Ans : Phenolphthalein

5) When a solution is added to a cloth strip treated with onion extract , then the smell of onion can not be detected . State whether the solution is an acid or base .

Ans : it  basic solution. 

When a basic solution is added to a cloth strip it is treated with onion extract .then smell of onion extract can not be detected.

Onion extract is olfactory indicator .

6) When a solution is added to Vanilla extract, then the characteristics smell of vanilla can not be determined. State the whether the given solution is an acid or a base .

Ans : the solution is base .

When the vanilla extract added in acid it’s smell does not vanish. But it is added in base , the smell of vanilla extract is vanished .

7) How will you test for the gas which is liberated when hydrochloric acid react with an active metal ?

Ans : When the acids react with active metal to form salt solution alongwith hydrogen gas .

e.g. when zinc metal react with dilute sulphuric acid to form zinc sulphate and hydrogen gas .

Zn + H2SO4 -> ZnSO4 + H2

In this reaction the zinc metal displace hydrogen from sulphuric acid . And hydrogen gas is evolved .

Identification : Presence of Hydrogen gas is detected by  a bring a burning candle near to the mouth of test tube . If the gas is burn it gives pop sound . H2  is detected.

8) Name the gas evolved when dilute HCl reacts with sodium hydrogencarbonate . How is is recognised?.

Ans : When the sodium hydrogencarbonate is react with HCl to form sodium chloride , carbon dioxide gas and water .

NaHCO3 (S) + HCL (aq) –> NaCl (aq) + Co2 + H2O

Sodium Hydrogen Carbonate +  Hydrogen Chloride –> Sodium Chloride + Carbon Dioxide +  Water

Carbon dioxide gas is evolved.

Identification : the gas is detected by the passing lime water . If the CO2  gas is evolved the lime water [Ca(OH)2] .

9) Give the name and formulae of two string base and strong acids

Ans :

Strong acids :  1) sulphuric acid is strong acid . Chemical formula of sulphuric acid is H2SO4

2) Nitric acid is strong acid . Chemical formula of nitric acid HNO 3

Weak acid : 1) formic acid is weak acid . Chemical formula of formic acid is CH2O 2

2) Citric acid is weak acid .Chemical formula of citric  acid is C6H 8O7

10) Name one natural source of each of the fallowing acids

a) Citric acid : citric acid is in lemon and barriers

b) Oxalic acid :. Oxalic acid is in Beets and tomatoes

C) Lactic acid :. Lactic acid is in milk , yogurt and sour cream

d) Tartaric acid : tartaric Is in grapes and Tamarind .

11) Name one animal and one plant whose stings contain formic acid ( or methanoic acid)

Ans :

Animal – Ant stings

Plants –  Nettle leaf sting

12) How the concentration of hydronium ion ( H3O+ ) affected when the solution of an acid is diluted?

Ans:  When the solution of acid is diluted then the concentration of hydronium ion (H3O+ )  is decreases

13) Write a word equation and then balanced chemical equation for the reaction taking place when ?

a) Dilute sulphuric acid is react with zinc granules

Ans – When dilute sulphuric acid is react with zinc granules to form zinc sulphate and hydrogen gas

Sulphuric acid + Zinc –> Zinc Sulphate + Hydrogen gas

The word equation for above reaction is

The chemical formula of sulphuric acid is  H 2 SO 4

The symbol of Zinc is Zn

The chemical formula of zinc sulphate is ZnSO4

The symbol of hydrogen gas is H 2

After adding the chemical formulae and symbol the reaction is becomes as

H2SO4 + Zn –> ZnSO4 + H2

 Balancing chemical equation: count the number of atom present on both the sides

Equal number of atom is present

Balanced chemical equation is

H2SO4 + Zn –> ZnSO4 + H2

b) dilute hydrochloric acid is react with magnesium ribbon

Ans : when dilute hydrochloric acid is react with magnesium ribbon to form magnesium chloride and hydrogen gas

Word equation of above reaction is

Hydrochloric acid + Magnesium –> Magnesium chloride + Hydrogen

Chemical formula of hydrochloric acid is HCl

Symbol of magnesium is Mg

Chemical formula of magnesium chloride is MgCl2

Symbol of hydrogen gas is H 2

Adding the chemical formulae the reaction is becomes as

HCL + Mg –> MgCl2 + H2

Balancing chemical equation :

First count the number of atom present on both the sides

Name of element

Reactant side Product side
Hydrogen 1

2

Chlorine

1 2
Magnesium 1

1


To equal the magnesium and chlorine atom on reactant side . Multiply HCl by 2 and write it 2 HCl .

2HCL + Mg –> MgCl2 + H2

Again count the number of atom . Equal number of atom present on both the sides

Balanced chemical equation is

2HCL + Mg –> MgCl2 + H2

C) sulphuric acid reacts with Aluminium powder

– when sulphuric acid is combine with aluminium powder to form Aluminium sulphate and hydrogen gas.

Word equation of above reaction is

Sulphuric acid + Aluminium –> Aluminium Sulphate + Hydrogen

Chemical formula of sulphuric acid is  H 2 SO 4

Symbol of Aluminium is Al

Chemical formula of Aluminium sulphate is Al 2 ( SO 4 ) 3

Symbol of hydrogen gas is H 2

After adding the chemical formula the chemical equation is becomes as

H2So4 + Al –> Al2(So4)3 + H2

Balancing chemical equation

Count the number of atom present on both the sides

No of element

Reactant side Product side
Hydrogen 2

2

Sulphur

1 3
Oxygen 4

12

Aluminium

1

2

To equal the Sulphur and oxygen atom  and aluminium at reactant side , multiply H2 SO4  by 3 And write. It 3H2SO4 . And multiply aluminium by 2 and write it 2Al The chemical equation is becomes as

3H2So4 + 2Al –> Al2(So4)3 + H2

Again count the number of atom,

At left hand side 6 hydrogen atom and right hand side 2 hydrogen atom is present .to equal the hydrogen atom at right hand side multiply H 2  by 2 and write it 2 H 2

The chemical equation is becomes as

3H2So4 + 2Al –> Al2(So4)3 + 3H2

Further count the number of atom . Equal number of atom is present

Balanced chemical equation is :

3H2So4 + 2Al –> Al2(So4)3 + 3H2

d) dilute hydrochloric acid react with iron filing

Ans –  when dilute hydrochloric acid is combined with iron filing to form ferrous chloride and hydrogen gas

Word equation of above reaction is

Hydrochloric acid + Iron —> Ferrous Chloride + Hydrogen gas

Chemical formula of hydrochloric acid is HCl

Symbol of iron is Fe

Chemical formula of ferrous chloride is FeCl2

Symbol of hydrogen is H 2

After adding the formulae and symbol the chemical equation is becomes as

HCL + Fe –> FeCl2 + H2

Balancing chemical equation

Count the number of present on both the sides

HCL + Fe –> FeCl2 + H2

At left hand side 1 chlorine, 1 hydrogen and 1 ferrous atom is present at right hand side 1 ferrous atom , 2 chlorine atom and 2 hydrogen atom is present

To equal the chlorine and hydrogen atom multiply HCl by 2 and write chemical equation

Balanced chemical equation is

2HCL + Fe –> FeCl2 + H2

14) Complete and balanced the chemical equation

a) Zn ( s) + HCl( aq) ——> ——————- + ————-

Ans : the complete balanced  chemical equation is

Zn (s) + 2HCL (aq) –> ZnCl2 (s) + H2 (g)

B) Na 2 CO 3 ( s) + HCl( aq) —->    —————- + ————+ ——–

Ans :.  The complete balanced chemical equation is

Na2Co3 (s) + 2HCL (aq) —> 2Nacl (aq) + Co2 (g) + H2O (l)

c) NaHCO3 ( s) + HCl(aq) —-> ————- + ———- + ——

Ans : the complete balanced chemical equation is

NaHCO3 ( s) + HCl(aq) —> NaCl (aq) + Co2 (g) + H2O (l)

d) NaOH( aq ) + HCl(aq ) —> ———- + ——–

Ans : the complete balanced chemical equation is

NaOH( aq ) + HCl(aq ) —-> NaCl (aq) + H2O (l)

e) CuO( s) + HCl( aq ) —> ———— + ———-

Ans : the complete balanced chemical equation is

CuO (s) + 2HCL (aq) —> CuCl2 (aq) + H2O (l)

Short type questions:

16) a) What is an indicator? Name three common indicator.

Ans :  Indicator is an one type of dye that shows changes colours when it is add in an acid or a base.

Indicator Is differentiate acid and base by showing colour changes.

Simply we said that indicator is a chemical substance which differentiate the acid and base by showing physical changes (odour) in it .

Example: three common indicator is litmus, phenolphthalein and methyl orange

Litmus : litmus show colour changes in acid is blue to red . And in basic solution is red to blue

Phenolphthalein: phenolphthalein indicator indicate colourless nature in acid

And pink colour in base (alkali)

Methyl orange : Methyl orange gives red colour in acid solution .

And methyl orange gives yellow colour in basic solution

b) Name the acid base indicator extracted form lichen

Ans : litmus  is an acid base indicator which is extracted from lichen. It is natural indicator which show purple dye colour. extracted from lichen plant which is belongs to division Thallophyta

c) What colour does the turmeric paper turn when put in an alkaline solution ?

Ans : When a turmeric paper put in alkaline solution it turns into red colour

Turmeric paper show colour changes from yellow to red.

17) What is an olfactory indicator ? Name two olfactory indicator . What is the effect of adding sodium hydroxide solution to these olfactory indicators ?

Ans : Olfactory Indicator : the substance whose odour (smell) changes in acidic or basic solutions are called olfactory indicator .

Olfactory means relating to the senses of smell.

Olfactory indicator shows different odour in acid and base solutions.

Olfactory indicator work on the principle that, when it is added in acid or base then it is characterised smell can not be detected

Examples :  1) onion extract – when it is added in base solution it smell can not be   detected

When it is added in acidic solution smell of onion extract is remains in it .smell is not destroy

  • Vanilla extract: when it is added in base solution smell of vanilla extract can not be detected.

When it is added in acid solution the smell of vanilla extract is remains in it.

  • When sodium hydroxide solution is added to cloth strip of onion extract .the smell of onion extract can not be detected. It show that when a base is added in onion extract the smell is vanished

When sodium extract solution is added in vanilla extract then the smell of vanilla extract can not be detected.

18) a) What’s happens when acid reacts with a metal ? Give chemical equation of the reaction involved?

When a metal react with acid to form their salt and evolution of hydrogen gas . Indication of evolution of hydrogen gas is giving by pop sound .

General equation for the reaction is:

Metal + acid —> salt  + Hydrogen gas

Example : When magnesium metal react with hydro chloric acid to form Magnesium chloride and evolution of hydrogen gas

2HCL (aq) + Mg –> MgCl2 (aq) + H2 ↑ (g)

Hydrochloric Acid Magnesium Metal Magnesium Chloride Hydrogen

  1. b) Which gas is usually liberate when an acid reacts with metals ? How will you test for the presence of this gas ? .

Ans : Hydrogen gas is liberated when an acid is react with metals

Test for the hydrogen gas :

Consider a reaction, in which zinc metal is react with sulphuric acid to form zinc sulphate with evolution of hydrogen gas.

Zn (s) + H2SO4 (aq) —> ZnSO4 + H2 (g)

Zinc  Sulphuric acid  Zinc Sulphate Water

Take a few piece of zinc granules in test tube . Add 5 ml of dilute sulphuric acid. After that formation of gas bubbles takes place .this gas is passing through the soup solution. Gas bubbles are also formed in soup solution. It is evolved in the atmosphere . Took near the burning candle of a gas filled soap bubbles. The soap bubbles burns and gives pop sound . This pop sound indicate that the presence of hydrogen gas

The pop sound shows the hydrogen gas produced in the reaction .

This is the test for hydrogen gas .

19) While diluting an acid , why it is  recommended that the acid should be added to water and not water to the acids?

Ans : When the water is added in concentrated acid for the dilution. The large amount of heat is evolved. It is exothermic reaction. This heat is changes into steam. Which can be exposed to our cloth and face. It causes damage and injury

While concentrated acid is added to water for dilution heat is evolved gradually . This is absorb by water do not cause any damage

Hence acid is added in water not water is added in acids .

20)  What’s happened when an acid is react with metal hydrogencarbonate ? Write equation of the reaction which takes place

Ans : When a acid is react with metal hydrogencarbonate to form their salt , water and evolution of carbon dioxide gas.

Metal Hydrogen Carbonate + Acid  —> Salt + Carbon di oxide + Water

Example: When dilute hydrochloric acid is react with sodium hydrogen carbonate .then sodium chloride, carbon dioxide and water is formed.

NaHCO3 (s) + HCL (aq) —> Nacl (aq) + Co2 (g) + H2O (l)

Sodium Hydrogen Carbonate Hydro Chloric acid —> Sodium Chloride Carbon dioxide Water

In above reaction sodium chloride salt is form with evolution of carbon dioxide gas.

21) a)  What’s happen when a dilute hydrochloric acid is added to sodium carbonate ?  Write a balanced chemical equation for the reaction involved?

Ans : When a dilute hydrochloric acid is added in sodium carbonate to form sodium chloride , carbon dioxide gas and water is formed.

Dilute Hydrochloric acid + Sodium Carbonate —> Sodium Chloride + Carbon dioxide + Water

The chemical equation of the reaction is

Balancing chemical equation:

Na2CO3 + HCL —> NaCl + Co2 + H2O

Count the number of atom present on both the sides

Name of the atoms

Reactant side Product side
Sodium 2

1

Carbon

1 1
Oxygen 3

3

Hydrogen

1 2
Chlorine 1

1


At reactant side 2 sodium atom, 1 carbon atom, 3 oxygen atom ,1 carbon atom and 1 chlorine atom is present

At product side, 1 sodium atom, 1 carbon atom 3 oxygen atom ,2 hydrogen atom and 1 chlorine atom is present

To equal the sodium and chlorine atom multiply HCl by 2 and write it 2 HCl . And multiply NaCl by 2 and write it 2NaCl

Na2CO3 + 2HCL —> 2NaCl + Co2 + H2O

Again count the number of atom present on both the sides

Equal number of atom is present , the balanced chemical equation is

Na2CO3 + HCL —> NaCl + Co2 + H2O

Sodium Carbonate  Hydro Chloric Acid —> Sodium Chloride Carbon dioxide Water

b) Which gas is liberated when dilute hydrochloric acid react with sodium carbonate ? How will you test for the presence of this gas?

Ans : When dilute hydrochloric acid is  react with sodium carbonate the carbon dioxide gas is liberated.

Test : Take 0.5 gram of sodium carbonate solutionsin Boiling test tubes. Add 2 ml of dilute HCl to observe that effervesces of a gas this gas is passed through a lime water After the passing gas the lime water becomes milky.

Keep passing gas in milky lime water, after some time lime water becomes clear .

The lime water becomes milky is indicated that the evolution of carbon dioxide gas.

22) What happens when an acid react with a base ? Explain by taking the example of hydrochloric acid  and sodium hydroxide . Give equation of the chemical reaction which takes place. What is the special name of such a reaction.

Ans : When an acid Is react with base to form the salt and water .

Acid + Base –> Salt + Water

In above reaction the acid nullified basic character and base nullified the acidic character to form neutral compound salt .

It is called neutralisation reaction.

Example : when  hydrochloric acid reacts with sodium hydroxide solution .the sodium hydroxide solution neutralised the acidity of Hydrochloric acid  to form sodium chloride salt and water.

NaOH (aq) + HCL —> NaCl (aq) + H2O (l)

Sodium Hydroxide Hydrochloric acid  Sodium Chloride Water

In the reaction sodium hydroxide and hydrochloric acid is neutralised each other and form salt. Which is not acid or base. It is neutral in nature.

23) What’s happens when an acid reacts with a metal oxide ? Explain with the help of an example . Write a balanced chemical equation for the reaction involved.

Metal Oxide + Acid —> Salt + Water

Ans : When acid is react with metal oxide to form salt and water .

It is neutralisation reaction . In this reaction acid and metal oxide is neutralised each other .

Example : when copper oxide is react with dilute hydrochloric acid to form copper chloride and water

CuO (s) + H2SO4 (aq) —> CuSO4 (aq) + H2O (l)

Copper Oxide (black) Sulphuric acid  Copper Sulphate (blue) Water

In this reaction black colour of copper oxide solution is changes  to blue colour of copper sulphate solution

Balancing chemical equation : Count the number of atom present on both the sides.

 Name of atoms

 Reactant side Product side
Copper 1

1

Oxygen

5 5
Hydrogen 2

2

Sulphur

1

1

Equal number of atom is present on both the sides.

The balanced chemical equation is

CuO (s) + H2SO4 (aq) —> CuSO4 (aq) + H2O (l)

Copper Oxide Sulphuric acid  Copper Sulphate Water

24) a) What are organic acid and mineral acid.

Ans :  Organic acid : those acid which are occuring Naturally is called organic acid . It is extracted from natural source like as plant materials and animals

Organic acid is weak acid because of it is naturally occurring .

The substance which contain organic acid which is not harmful to eat and drink .

Example: acetic acid, citric acid , lactic acid , tartaric acid . It is an organic acid.

Lactic acid is obtained from sour milk ( curd ) . Tartaric acid is present in tamarindand unripe grapes .

Mineral acid : those substance which is prepared from minerals on the earth are  called mineral acid .

Mineral acid is called man made acid

Mineral acid are harmful  .they burn hand and cloths . In laboratory dilute acid is used . It is less harmful than concentrated acid .

Example: Hydrochloric acid, Sulphuric acid and Nitric acid etc are mineral acid.

b) Give two example each of organic acid and minerals acids

Ans Organic acid : acetic acid and oxalic acid is an example of organic acid

Minerals acid : sulphuric acid and nitric acid is an minerals acid .

C) State some of the uses of minerals acid in industry .

Ans : Sulphuric acid :  Sulphuric acid is used in the manufacturing of fertilisers like ammonium sulphate.

It is use to make paints , synthetic fibres and  chemicals.

It is mostly use in detergents , explosives and car batteries.

Nitric acid : Nitric acid is used for making fertilisers like ammonium nitrate.

It is also used to make explosive like TNT (Tri – Nitro Toluene )

It is use to make dyes and plastics

Hydrochloric acid : before the galvanisation process hydrochloric acid is used to remove oxide from steel object .

It is also use for removing scale deposits from inside the boilers

It is mostly use to make dye – stuff, textile food and in leather industry.

25) What is mean by strong acid and weak acid ? Classify the fallowing into string acid and weak acid

HCl , CH3 COOH , H SO 4 , HNO 3 , H 2 CO 3 ,H 5SO 3

Ans : Strong acid : the acid which is completely dissociate and form their ions is called strong acid.

Strong acid gives large amount of Hydrogen ions in water.

Generally minerals acid are strong acid.  Strong acid is harmful and dangerous to hand.

Strong word refers to degree of ionisation not concentration of the acids.

Strong acids have high electrical conductivity and they are strong electrolyte.

e.g. hydrochloric acid is completely ionised in water.

HCl  —> H + + Cl

Single arrow pointing towards the right indicate that the HCl is completely ionised to form ions.

Weak electrolyte : the acid which is partially dissociate in their ions is called weak acids .

Weak acid gives less amount of hydrogen ions in water .

Organic acids are weak acids . It is safe to eat and drink .dilute solution of weak acids are quite safe to drink.

Weak acids are quite react with other substances such as metal, metal carbonates, metal hydrogen carbonates.

Weak acid have low electrical conductivity. Weak  acids is weak electrolytes

e.g. acetic acid is partially ionised in water to produced only a small amount of hydrogen ions

CH3COOH    ⇌   COO  + H +

The double arrow pointing towards left as well as right is indicate that acetic acid does not ionised fully to form hydrogen ions .

  • Strong acids – HCl , H 2 SO 4 ,HNO 3
  • Weak acids –CH3COOH , H2CO3 , H2SO3

26) Why do HCl ,H2SO4 ,HNO3 , show acidic character in aqueous solution while solution of compound like C6H12 O6 (glucose) and C2H5OH (alcohol) do not show acidic character.

Ans – The acid like HCl,  ,H2SO4, HNO3, is mixed in water and it is completely ionised into their ions. To form a hydrogen ions (H+)  in the water .acidic character is shown by Formation of H + Ions.

But when C6H12O6 (glucose ) and C2H5OH (alcohol) is mixed in water do not dissociate into ions . Do not form Hydrogen ions any other ions . Hence it is not show acidic character.

27) What is neutralisation reaction? Explain with an example. Give the chemical equation of the reaction which takes place.

Ans: the reaction in which acid and base react with each other to form salt and water  is called neutralisation reaction.

Acid + Base —> Salt + Water

In the through out the reaction acid is treated with base . The base neutralises the acid and destroy acidic character. And acid neutralised the base and destroy the basic character.

Simply called that when the effect of acid is Nullified by base and vice versa is called Neutralisation reaction .

e.g. When the sulphuric acid is react with sodium hydroxide to form sodium sulphate salt and water

H2SO4 (aq) + NaOH (aq) —-> Na2SO4 (aq) + H2O (l)

Sulphuric acid Sodium Hydroxide Sodium Sulphate Water

In the above process the H 2 SO 4  and NaOH neutralised (Nullify) each other and form sodium sulphate salt, which is neutral in nature

Aqueous solution of sulphuric acid is neutralised by aqueous solution of sodium hydroxide .

28) Why should curd and other food stuff (like lemon juice etc) not be kept in a metal container (such as copper and bronze vessels )

Ans : When the curd and other sour food stuff ( like lemon juice ) are kept in metal container , it is react with metal of the vessels to form a poisonous metal compound . Due to this compound cause food poisoning and damage to health

Hence curd and other food stuff are not kept in metal container.

29) a) What is produce if an acid is added to base

Ans : when an acid is added to base to form salt and water.

It is neutralisation reaction . In which acid in nullify the base and vice versa.

b) Why does the dry HCl gas not change the colour of dry litmus paper

Ans : Colour of litmus paper changes shown only when formation of hydrogen ions (H +) in solution

The dry HCl do not produce H + Ions . When it is mixed with water in aqueous state it form H + ions . Acidic character is depend upon the amount of H + ions produced .litmus paper shows the acidic and basic character . When dry HCl gas passed through a litmus paper the H + ions didn’t produce.  Litmus paper can not get any result .

Hence dry litmus paper do not show any changes of colour of dry HCl gas .

c) What colour does the phenolphthalein indicator turns when added to an alkali ( such as sodium hydroxide)

Ans :  Pink colour  Solution is form when the phenolphthalein indicator is added to alkali ( sodium hydroxide ).

30)  a) Why do acid not show an acidic behaviour in absence of water ? .

Ans : Acidic behaviour of acid is due to presence of Hydrogen ions (H + ) . When acid is react with water it ionised and form hydrogen ions . In absence of water do not produce hydrogen ions (H + ) it can not ionised. Hence water is responsible for acidic behaviour for the formation of hydrogen ions .

Acidic character is totally depend upon the formation hydrogen ion.

b) Why does an aqueous solution of an acid conduct electricity?

Ans :. When an acid is dissolve in water to form aqueous solution. In the aqueous solution acid is ionised and form it’s ions. Acid is dissolved into the hydrogen ions.  It is charge particles .due to the presence of charge particles. (Ions) the aqueous solution of acid is conduct electricity.

E.g. when hydrochloric acid (HCl ) is dissolved in water the aqueous solution of hydrochloric acid is formed . In the solution of HCl is ionised into Hydrogen ions ( H + ) and chloride ions ( Cl ) the ions is charge particles . They have positive and negative charge. This charge particles ( ions ) conduct electricity . Due to the presence of  H +  and Cl ions in the solution of HCl is conduct electricity.

c) Why does the distilled water not conduct electricity and rain water does ?

Ans : Distilled water do not have any ionic compounds. Ionic compound is responsible to conduct electricity. Ions have an charge on it .charge particles is conduct electricity it means that in distilled water does not present of free ions in it. It is not acidic or basic in nature . hence distilled water do not conduct electricity.

But in the ain water when it falling to the earth surface through atmosphere. The acidic gas carbon dioxide is dissolved in it to form carbonic acid (H2CO3 ) . Carbonic acid is ionised into hydrogen ions H + (aq) and Carbonic ions CO 3 2-aq this ions conduct electricity .also in rain water the other acidic gas such as SO2 , NO2  is mixed and form acid which is also responsible to conduct electricity.

Long Answer Type Questions:

31.)  (a) What happens when an acid reacts with a metal carbonate? Explain with the help of  example. Write chemical equation of the reaction involved

Ans : (a) When an acid reacts with a metal carbonate to form, carbon dioxide gas and water is formed.

Metal Carbonate + Acid  —>  Salt + Carbon dioxide +  Water

Example : When hydrochloric acid reacts with sodium carbonate to form sodium chloride carbon dioxide & water are formed.

Na2CO3 (s)  + 2HCL (aq) —> 2NaCl (s) + Co2 + H2O

Sodium Carbonate Hydrochloric acid    Sodium Chloride Carbon dioxide Water

The brisk effervescence of carbon dioxide gas is formed. The rapid escape of small bubble of gas from the liquid

(b) What happens when carbon dioxide gas is passed through lime water:

i) For a short time ?

ii) For a considerable time ?

Write equation of the reaction involved.

Ans :  (i) For a short time :  When carbon dioxide gas is passed through lime water for short time then the milky calcium carbonate and water formed

Ca(OH)2 (aq) + Co2 (g) —> CaCo3 (s) + H2O

Calcium Hydroxide (lime water)  Carbon dioxide    Calcium Carbonate (White p.p.t.) (Makes lime Water milky)   Water

In the reaction the lime water turns milky because the formation of a white precipitate of calcium carbonate.

(ii) for a considerable time :  when a carbon dioxide gas is passed through lime water for a long then calcium hydrogen carbonate is formed

CaCo3 (s) + Co2 (g) + H2O (l) —> Ca(HCO3) (aq)

Calcium Carbonate Carbon di oxide Water  Calcium Hydrogen Carbonate

The lime water becomes milky in short time is dissolve and solution becomes clear.

32.) With the help of labelled diagrams, describe an activity to show that acids produce ions only in aqueous solutions.

Ans :  The following experiment shows the acids produce ions only in aqueous solutions :

1) Take 1 gram of solid sodium chloride (NaCl) in clean & dry boiling tube . add some concentrated sulphuric acid. After that fit a rubber cork with a small glass delivery tube in the mouth of boiling tube .

The sodium chloride sulphuric acid is react with each other &formed  Hydrochloric acid gas .

This gas is coming out from test tube at open end of glass tube.

2) Hold a dry blue litmus paper at the open mouth of gas tube. No change in colour occurs at dry blue litmus paper.

3) Again hold wet ( moist) blue litmus paper in hydrogen chloride gas. The blue litmus paper changes to red in colour.

Conclusion : Dry HCl gas does not contain any Hydrogen ions in it, hence dry HCl gas does not shows change the colour of dry blue litmus paper because it has no hydrogen ions ( H+) aq.

Hydrogen chloride gas dissolve in water to produce Hydrogen ions (H+)aq and chloride ion Cl (aq). The separation (H+)  ions from HCl molecules can occurs only in the presence of water.

In another way it is written as, when HCl is dissolving to form  hydrogen ions . It is also written in the form of Hydronium ions.

HCL + H2O —> H3O+ + Cl

Hydrochloric acid Water  Hydrogen Ion Chlorine ions

H+ ions indicate HCl is acidic . Hence the dry HCl turns wet blue litmus paper .

It dissolves in the water present in wet litmus paper to forms Hydrogen ions ( H+ aq) which turns blue litmus paper to red.

Above activity indicate that HCl gas shows  ions only in aqueous solution.

33.)  (a) Which element is common to all acids ?

Ans :  (a) Hydrogen is the common element in to all the acids.

b) Compounds such as alcohol and glucose also contain hydrogen but are not categorised as acids. Describe an activity to prove it.

Take solution of hydrochloric acid sulphuric acid glucose & alcohol.

Pour the hydrochloric acid, sulphuric acid, glucose and alcohol in beaker A,B,C,D respectively.

ii) Fix two iron nails on a Rubber cork and place the cork in beaker. (A) connect the nails to the two terminals of a 6 volt battery through a switch and a bulb. Switch on the current at beaker A the bulb start glowing. This indicate that the hydrochloric acid (HCl)  solution taken in the beaker conduct electricity.

iii) Repeat the experiment at beaker B,  the bulb glow again. This is shows  that sulphuric acid conducts electricity.

iv) Again the switch on the current at beaker C, the bulb does not glow in the case this show that glucose solution does not conduct electricity.

iv) Lastly switch on the current at beaker D . the bulb does not glow in this beaker . This shows that alcohol solution does not conduct electricity.

Conclusion : The acid solution i.e. Hydrochloric acid (HCl) & Sulphuric acid (H2SO4) conduct electricity because it dissociate into charge particles [ions] .this charge particles carry currents but in the case of glucose &alcohol is not form charge particles. Due to the absence of ions glucose solution & alcohol solution do not conduct electricity.

 

Lakhmir Singh Manjit Kaur Class 10 Chemistry 2nd Chapter Solution (2nd Part)

 

Bases

Very Short Answer Type Questions :

1) Name the gas evolved when zinc granules are treated or heated with:

  • Hydrochloric acid solution
  • Sodium hydroxide solution

Ans : (a) When a zinc granules is treated with hydrochloric acid solution to form zinc chloride salt with the evolution of hydrogen gas.

2HCL + Zn ……..> ZnCl2 + H2

By treating with hydrochloric acid [HCl] hydrogen gas is evolved.

(b) When a zinc granules is treated with sodium hydroxide solution to form sodium zincate with the evolution of hydrogen gas.

2NaOH (aq) + Zn (s) Zinc granules …….> Na2ZnO2 (aq) + H2 (G)

(Sodium hydroxide) + (Zinc granules)    (Sodium zincates) (hydrogen gas)

By treating with sodium hydroxide [NaOH] Hydrogen gas is evolved .

 

2) What is the common name of water soluble bases.?

Ans:  The common name water soluble bases is alkali.

Example : Sodium hydroxide [NaOH]  potassium hydroxide [KOH], Calcium Hydroxide [ Ca(OH)2] .

 

3) What is the common in all the water soluble bases (or alkalis) ?

Ans : All water soluble bases (or alkali) formed hydroxide ions [OH} in water.

 

4) Why does tooth decay start when the pH of mouth is lower than 5.5?

Ans: Food contains sugar , this sugar breakdown in our mount to form acids because of bacteria present in mouth . this acid lower the pH in the mouth and tooth decay starts .  the tooth enamel is made of calcium phosphate . which is hardest material in our body but acid is strong enough to attack the enamel of our tooth and it get corroded. This corrosion occurs at the lower PH of mouth . Due to this corrosion tooth decay starts .

 

5) What is the pH of neutral solution?

Ans : The pH of neutral solution is exactly 7. neutral solution does  not shows any effect of litmus or any other common indicator.

 

6) Which is more acidic : a solution of pH = 2 or a solution of pH = 6?

Ans : The solution of pH = 2 is more acidic than the pH= 6. Because pH = 2 solution contain higher number of concentration of hydrogen ions.

 

7) Which more basic (or more alkaline ) : a solution of pH= 8 or a solution of pH = 11 ?

Ans : The solution of pH= 11 is more basic than the solution of pH = 8 . because the solution of pH = 11  contain higher concentration of hydroxide ions [OH-] . so it is strong alkali.

 

8) Name the scientist who developed the pH scale.

Ans : In 1909,  scientist `Sorenson’ developed the pH scale.

 

9) Name the indicator which can give us an idea of how strong or weak acid or base is.

Ans : The indicator which can gives the idea of how strong or weak an acid or base is called universal indicator.

 

10) The of soil A is 7.5 while that of soil B is 4.5. Which of the two soils, A or B should be treated with powdered chalk to adjust its pH and why?

Ans : pH of soil A is 7.5 ,  it is basic in nature and pH of soil B is 4.5,  it is acidic in nature. as well as the powdered chalk [CaCO3] is basic in nature . Hence soil B which have pH 4.5 is adjust their pH when it is treated with powdered chalk. Because soil B is very acidic in nature and its acidity is reduced by adding powdered chalk, which is basic in nature.

 

11) What is the name of the indicator which can be used for testing the pH of a solution?

Ans : The indicator which can be used for testing the pH of a solution is called universal indicator. Universal indicator shows the strength of acid & base by measuring the pH of acid & base.

 

12) What color will universal indicator show if you add it to the following substances.

  • Potassium hydroxide, pH = 12
  • Soda water, pH=5
  • Sulphur acid, pH= 2

Ans : (a) In potassium hydroxide (which have PH = 12 ) Add universal indicator, after addition  potassium hydroxide show Dark purple colour. Formation of Dark purple color indicate that the potassium hydroxide is strong alkali.

(b) In soda water ( which have pH = 5) . add universal indicator, after addition  soda water shows orange yellow colour.

Formation of orange yellow colour indicate that the soda water is weak acid.

(c) In sulphuric acid ( which have pH= 2 ) add universal indicator then sulphuric acid shows red colour.

Formation of red colour indicate that the sulphuric acid is strong acid .

 

13) A beaker of concentrated hydrochloric acid has a pH of 1. What colour will full range universal indicator turn if it is added to this beaker? Is it a strong or a weak acid ?

Ans : When universal indicator is add in a concentrated Hydrochloric acid has a pH 1. Then the colour of hydrochloric acid solution is changes to red. red colour  is formed because pH of concentrated Hydrochloric acid is very low. It is strong acid. Strong acid shows red colour in universal indicator

 

14) Two solutions X and Y are tested with universal indicator. Solution X turns orange whereas solution Y turns red. Which of the solutions is a stronger acid?

Ans : Two solution X and Y tested with universal indicator solution X turns orange colour whereas solution Y turns red in colour. Red colour solution Y is stronger acid because the solution which impart red colour is a strong acid .

 

15) Two solution A and B have pH values of 3.0 and 9.5 respectively. Which of these will turn litmus solution from blue to red and which will turns phenolphthalein from colourless to pink?

Ans : Solution A has pH 3.0 ,when it is tested with litmus paper it shows the blue litmus paper turns into red.   Change in colour from blue to red indicate that the solution A is acid . which pH has very low. Solution B has pH 9.5 ,when it is tested with phenolphthalein indicator ,it shows the pink colour. Change in colour from colourless to pink . indicate that the solution B is basic [ alkali ] which pH is high.

 

16) Two drinks P and Q gave acidic and alkaline reactions, respectively. Which solution will give alkaline reaction and which one acidic ?

Ans : Drink P is acidic and Drink Q is alkaline in nature . drink Q pH value is 9 because drink Q is alkaline and alkaline and alkaline solution. Shows pH value between 7 to 14. Hence drink Q pH value is 9.

 

17) Two solutions X and Y have pH=4 and pH=8 , respectively. Which solution will give alkaline reaction and which one acidic?

Ans : The solution X value pH is 4 and solution Y pH value is 8.

Solution X shows acidic reaction because it’s PH is 4 . The pH between 1 to 7 acidic in nature solution Y show alkaline reaction because its pH is 8 . the pH between 7 to 14 shows basic it nature.

 

18) Fill in the following blanks with suitable words:

(a ) Acids have a pH———than 7.

(b ) Alkalis have a pH——— than 7.

(c ) Neutral substances have a pH of———-.

(d ) The more acidic a solution, the————- the pH.

(e ) The more alkaline a solution, the ————the pH.

Ans : (a ) lower  ( b) Higher  ( c) 7  (d ) lower  (e) higher.

 

Short Answer Type Questions in PDF Format

Short ans type 1

 

Long Answer Type Questions in PDF Format

LOng ans type

 

Lakhmir Singh Manjit Kaur Class 10 Chemistry 2nd Chapter Solution (3rd Part)

Very short Answer Type questions

1) What is the chemical formula of (a) baking soda, and (b) washing soda?

Ans:  (a) Chemical formula of Baking soda is NaHCo3.

The chemical name of baking soda is Sodium Hydrogen Carbonate.  Generally it is called as Sodium Bicarbonate.

(b) Chemical formula of washing soda is Na2Co3.10H2O.

In washing soda 10 molecule of Hydrogen is present it is called Sodium Carbonate decahydrate.

Chemical name of washing soda is Sodium Carbonate [Na2Co3].  Sodium Carbonate is commonly known as `Soda ash’.

 

2) Write chemical formula of (i) Soda ash (ii) sodium carbonate decahydrate.

Ans : (i) Soda ash– Chemical formula of Soda ash is Na2Co3.

Chemical name of Soda ash is sodiumcarbonate.

(ii) Sodium carbonate –  Chemical formula of sodium carbonate decahydrate is Na2Co3.10H2O.

 

3) State whether the following statement is true or false:

Copper sulphate crystals are always wet due to the presence of water of crystallisation in them.

Ans: It is False statement

because copper sulphur is not wet it is hydrated salt.

 

4) Which of the following salt has a blue colour and why?

CuSO4.H2 or  CuSO4

Ans: CuSO4.H2O  Salt have blue colour. It is an hydrated salt.

Which contained one water molecule which is the responsible for blue colour.

 

5) What should be the colour of litmus in a solution of sodium carbonate?

Ans: The Red litmus paper shows blue colour in the solution of sodium carbonate.

formation of blue colour indicate that solution of sodium carbonate is alkaline in nature.

 

6) State the common and chemical names of the compound formed when plaster of Paris is mixed with water.

Ans: When plaster of Paris is mixed with water to form calcium sulphate dihydrate.

CaSO4. ½H2O + 1½H2O —> CaSo4.2H2O

Plaster of Paris  Water  Gypsum [calcium sulphate dehydrate]

The common name of Calcium sulphate dihydrate is Gypsum.

 

7) With which substance should chlorine be treated to get bleaching powder?

Ans: When calcium hydroxide is treated with chlorine to form bleaching powder.

Ca(OH)2 + Cl2 —> CaOCl2 + H2O

Calcium Hydroxide  Chlorine  Calcium Oxychloride Water

 

8) What is the commercial name of calcium sulphate hemihydrates?

Ans: The commercial name of calcium sulphate hemihydrate is plaster of Paris [CaSO4. 1/2 H2O].

 

9) Name the product formed when Cl2and H2 produced during the electrolysis of brine are made to combine.

Ans: When a chlorine [Cl2] and Hydrogen [H2] is combine to form hydrochloric acid .

 

10) Name calcium compound which hardens on wetting with water.

Ans: The calcium compound of which is hardens on wetting with water is plaster of Paris. The chemical name of plaster of Paris is calcium sulphate hemihydrates.

 

11) Name sodium compound of which is a constituent of many dry soap powder.

Ans: Sodium carbonate [Na2CO3] or washing soda is constituent of many dry soap powder.

 

12) Name a metal carbonate which is soluble in water.

Ans: Sodium carbonate [Na2CO3] is soluble in water.

 

13) Name an acid which is present in baking powder.

Ans: The acid present in baking soda is Tartaric acid

 

14) Name the metal whose carbonate is known as washing soda.

Ans : Chemical formula of washing soda is Na2CO3.10H2O .

In the washing soda, sodium is the metal whose carbonate is known as washing soda.

 

15) Which compound is used as an antacid in medicine : NaHCO3 or Na2CO3?

Ans: NaHCO3(Sodium hydrogen carbonate) is used as an antacid in medicine because it is alkaline is nature when it is react with the acid present in stomach, it get neutralized easily. And get relief to stomach for digestion.

 

16) What is the common name of (a) NaHCO3 and (b) Na2CO3.10H2O?

Ans: a) NaHCO3 :  Common name of NaHCO3  is baking soda.

b) Na2 CO10H2 O : Common name of Na2 CO3.10H2O of is washing soda.

 

17) Write the chemical name and formula of (a) common salt, and (b) caustic soda.

Ans: (a) Common salt : The chemical name of common salt is sodium chloride.

Chemical formula of common salt is Nacl.

(b) Caustic soda : The chemical name of caustic soda is sodium hydroxide.

Chemical formula of caustic soda is NaOH.

 

17) What are the two main ways in which common salt ( Sodium chloride) occurs in nature?

Ans:  The common salt (Sodium chloride) occurs naturally by two way which is sea water and as rock salt .

  • In sea water it is occurs as dissolved formed
  • In rock salt it is occurs as solid form

 

18) Name the major salt present in sea- water?

Ans: The major salt present in sae-water is Sodium chloride (NaCl)

 

19) How the common salt obtained from sea-water?

Ans: By the evaporation process common salt is obtained from sea-water.

 

20) Why is sodium chloride required in our body?

Ans: Sodium chloride is require in our body to formation of hydrochloric acid (HCL ) in stomach. For the digestion, and maintained the fluid in our blood cells also help to working of Nervous system.

 

21) Name three chemicals made from common salt (or sodium chloride).

Ans:  1) Sodium hydrogen carbonate [Baking soda] is made from sodium chloride.

2) Sodium carbonate [Na2CO3] – washing soda is also obtained from sodium chloride.

3) Sodium hydroxide [NaOH] is made from sodium chloride.

 

22) Give any two uses of common salt (sodium chloride).

Ans: 1) Common salt is use as preservative in Pickles and in curing meat and fish It is act as preservative.

2) Common salt (Sodium hydroxide) is used in the manufacturing of soap.

 

23) What name is given common salt which is mined from underground deposits? How was the salt formed?

Ans:  The salt which mined from underground deposits is called Rock salt. The salt is brown colour crystal which present on earth from thousand of year of ago. It is obtained from underground by mining process . This process is same as coal mining process.

 

24) Name the salt which is used as a preservative in pickles, and in curing meat and fish.

Ans:  Sodium chloride is used as a preservative pickles and in curing meat and fish.

 

25) Name the raw material used for the production of caustic soda.

Ans: Sodium chloride is used for produce caustic soda.

When sodium chloride is electrolytically decomposed the caustic soda is formed.

Sodium chloride is raw material use to production of caustic soda.

2NaCl + 2H2O —> 2NaOH + Cl2 + H2

Sodium Chloride Water  Sodium Hydroxide Chloride Hydrogen

 

26) The electrolysis of an aqueous solution of sodium chloride gives us three products. Name them.

Ans: When an aqueous solution of sodium chloride is electrolytically decomposed  to form sodium hydroxide, chloride and hydrogen gas.

2NaCl + 2H2O —> 2NaOH + Cl2 + H2

Sodium Chloride  Water  Sodium Hydroxide Chlorine Hydrogen

Sodium hydroxide is formed at near cathode chlorine gas is formed at anode hydrogen gas is formed at cathode.

 

27) During the electrolysis of a saturated solution of sodium chloride, where is :

(a) Chlorine formed?

(b) Hydrogen formed?

(c) Sodium hydroxide formed?

Ans:  (a) Chlorine is formed at anode.

(b) Hydrogen gas is formed at cathode.

(c) Sodium hydroxide gas is formed near the cathode.

 

30)

(a)

(b)

(c)

NaCl + NH3 + H2O + Co2 —> NaHCO3 + NH4Cl

(d)

Ca(OH)2 + Cl2 —> CaOCl2 + H2O

 

31)  What is washing soda? State two properties and two uses of washing soda.

Ans- Washing soda is sodium carbonate in which 10 molecules of water of crystallisation is present .  sodium carbonate decahydrate called as washing soda .

The chemical formula of washing soda is  Na2CO3.10H2O.

Washing soda is obtained from sodium chloride (NaCl)

Properties :

  • Washing soda present in crystalline solid structure form.
  • When red litmus paper is dipped into washing soda solution it change into blue colour . Changes in colour indicate that it is alkaline in nature

Uses :

  • In glass manufacturing process sodium carbonate is use .it is also use to manufacture soap and paper
  • Manufacturing of sodium compound ( borax ) takes place by using sodium carbonate .

 

32)  Write the formulae of sodium chloride and sodium carbonate. Explain why an aqueous solution of sodium chloride is neutral but an aqueous solution of sodium carbonate is basic ( or alkaline). Write chemical equations of the reaction involved.

Ans : The chemical formula of sodium chloride is NaCl

The chemical formula of sodium carbonate is Na2 Co3.

When sodium chloride dissolve in water to form an aqueous solution of sodium chloride. Dissociation process is takes place to form ions

Here from Positive ions is Na+  and Negative ion is Cl

There is no formation of hydrogen ion (H-) and hydroxy ions ( OH ) .Hydrogen ions  indicate acidic nature. And hydroxy  ion  (OH ) indicate basic nature. Hence sodium chloride show neutral nature.

  • But when sodium carbonate is dissolved in water hydrolysis process takes place to form sodium hydroxide (NaOH) and carbonic acid (H2CO3).

Sodium hydroxide is strong base and carbonic acid is weak base.

Na2Co3 (s) Sodium Carbonate + 2H2O(L) Water ⇋  2NaOH Sodium hydroxide (aq) + H2CO3 Carbonic acid (aq)

Sodium hydroxide is fully ionised gives large amount of hydroxide ions (OH-) & Carbonic acid slightly ionised to form a small amount of hydrogen ions (H-) . sodium carbonate [ Na2CO3] solution contain more hydroxide ions than  hydrogen ions Hence sodium carbonate is basic [ alkaline] in nature.

 

33) Write the chemical formula of ammonium chloride. Explain why an aqueous solution of ammonium chloride is acidic in nature ? illustrate your answer with the help of a chemical equation.

Ans : Chemical formula of ammonium chloride is NH4Cl.

The aqueous solution of ammonium chloride is acidic in nature because ammonium chloride is made from strong acid of hydrochloric acid (HCl) and weak base of ammonium hydroxide [NH4OH].

  • Explanation :

When ammonium chloride is dissolved in water it is hydrolysed to form Ammonium hydroxide and hydrochloric acid.

NH4Cl (s) Ammonium Chloride + H2O(L) Water NH4OH (Aq) Ammonium Hydroxide + HCL (Aq) Hydrochloric Acid

Ammonium hydroxide partially ionised to form a small amount of hydroxide ion.  [OH _ (aq)].  Hence it is weak base and hydrochloric acid [HCl] is fully ionised to form a large amount of hydrogen ions [ H+(aq)] hence it is strong acid.

In ammonium chloride solution large amount of hydrogen ions [H +(aq) ] is present than hydroxide ions hence ammonium chloride is acidic in nature.

 

34) What is baking soda? Write chemical name of baking soda . Give the important uses of baking soda. How does baking soda differ chemically from washing soda?

Ans :  Baking is a chemical substance which is add to the food for the increasing cooking capacity i.e. faster cooking.

  • The chemical name of baking soda is sodium hydrogen carbonate.
  • Chemical formula of baking soda is NaHCO3.
  • Baking soda is made from common salt [sodium chloride]

Uses :

  • it is used to remove excess of hydrochloric acid is present in the stomach . It is called acidity

It acts as an antacid to give relief from acidity

  • baking soda [ sodium hydrogen carbonate] with sulphuric acid is use in fire extinguisher to the formation of carbon dioxide gas
  • In the formation of baking powder process baking soda ( sodium hydrogen carbonate ) is used.

It’s  all about is uses of baking soda.

Different nature of baking soda from washing soda.

Washing soda is sodium decahydrate [ Na2CO3] and baking soda is sodium hydrogen carbonate [NaHCO3].In washing soda 10 molecule of water of crystallisation is present . And in baking soda zero molecule of water of crystallisation is present. baking soda & washing soda is differ  chemically by their formulae.

 

35) Describe how sodium hydrogencarbonate [baking soda] is produced on a large scale. Write equation of the reaction involved.

Ans : Sodium hydrogen carbonate is present on large scale by using raw material sodium chloride, Ammonia, carbon dioxide gas.

When a cold and concentrated Solution of sodium chloride is react with ammonia and carbon dioxide gas to form sodium hydrogen carbonate and ammonium chloride as a by product.

NaCl (Sodium Chloride)[Common salt] + NH3 (Ammonia) + H2O (Water) + CO2 Carbon dioxide  …..>   NaHCO3Sodium Hydrogen  Carbonate [Baking Soda] + NH4Cl Ammonium Chloride

Sodium hydrogen carbonate is formed as a white crystal. Which is alkaline in nature

 

36) What happens when a cold and concentrated solution of sodium chloride reacts with ammonia and carbon dioxide? Write the chemical equation of the reaction which takes place.

Ans : When a cold and concentrated solution of sodium chloride reacts with ammonia & carbon dioxide to form sodium hydrogen carbonate [baking soda] and ammonium chloride

NaCl (Sodium Chloride) + NH3 Ammonia + H2O Water + CO2 Carbon dioxide …….> NaHCO3 Sodium hydrogen Carbonate [Baking soda] + NH4Cl [Ammonium Chloride]

 

37)

(a) What is meant by “water of crystallisation” in a substance ? Explain with an example.

 (b) How would you show that blue copper sulphate crystals contain water of crystallisation?

(c ) Explain how anhydrous copper sulphate can be used to detect the presence of moisture ( water ) in a liquid.

Ans : (a) Water of crystallisation :

In some salt contain a few water molecules in their crystals structure as an essential part.

“The fixed number of water molecule is present in salt to form part of crystal of a structure is called water of crystallisation “

  • The salt which contain water of crystallisation is called hydrated salt.
  • In hydrated salt contain fixed number of water molecules in its formula unit.
  • Water of crystallisation is a part of crystal structure of salt.
  • Due to the water of crystallisation , salts crystal have definite shape and it imparts the colour.

Example : Iron Sulphate Heptahydrate  FeSO4. 7H2O

In Iron sulphate crystals 7 molecules of water of crystallisation is present in one  formula unit . it is written as FeSO4. 7H2O.

In which 7 molecules of water is present hence write Heptahydrate.

(b) In copper sulphate crystal 5 molecule of water of crystallisation is present in one Formula unit.

it is written as CuSo4.5H2O. it is Copper sulphate Pentahydrate. it show blue colour. Which indicate  that it contain water of crystallisation .

(c ) When water is added to anhydrous copper sulphate it gives blue colour .it indicate that the presence of moisture in a liquid.

  • Take white anhydrous powder  of copper sulphate in the test tube . add few drop of liquid [water] in it .the appearance of blue colour of anhydrous copper sulphate.

Appearance of blue colour indicate the presence of moisture.

CuSo4 Anhydrous Copper Sulphate [White] + 5H2O Water ………> CuSo4 . 5H2O Hydrated copper sulphate [Blue]

 

38)

(a) What is the common name of sodium hydrogencarbonate?

(b) What happens when a solution of sodium hydrogencarbonate is heated ? Write the equation of the reaction involved.

(c) Explain why, sodium hydrogencarbonate is used as an antacid.

Ans : (a) The common name of sodium hydrogen carbonate is baking soda.

(b) When solution of sodium hydrogen carbonate is heated it decomposes to form sodium carbonate , water  along with evolution of carbon dioxide gas.

                           Heat

2NaHCO3 Sodium Hydrogen Carbonate ..….…………> Na2CO3 + CO2 + H2O

  • It is decomposition reaction.
  • Above reaction clearly shows that when sodium hydrogen carbonate is heated to  gives carbon dioxide gas .  it is constituent  of baking powder

(c)  Sodium hydrogen carbonate is alkaline in nature . when it taken,  it neutralise the excess of hydrochloric acid  which ispresent in stomach and give  relieves for digestion.

Hence sodium hydrogen carbonate is act as an antacid.

 

39)

(a) What will happens if heating is not controlled while preparing plaster of Paris ?

(b) Write an equation to show the reaction between plaster of Paris and water.

Ans : (a) If heating is not controlled whilepreparing of plaster of Paris.  i.e. it is more than 1000C or above 373K then the water of crystallisation is eliminated or evaporated and anhydrous Calcium sulphate is formed. It means that after over heating  of Gypsum,  the dead burnt plaster is formed.

     More than 1000c

CaSo4 . 2H2O ……………………………….> CaSo4

(b) When water is added to plaster of Paris, it sets into a hard mass.

Hard mass is a gypsum. This Hard mass or solid is set in an half hour .

The chemical reaction involve in it, as follows :

CaSo4 . ½ H2O + 1½ H2O ……….> Caso4. 2H2O Gypsum [Sets as a hard mass]

 

40)

(a) What happens when copper sulphate crystals are heated strongly? Explain with the help of an equation.

(b) What happens when a few drops of water are added to anhydrous copper sulphate ? Explain with the help of an equation.

Ans : (a) When a blue copper sulphate crystal is heated strongly

The water of crystallisation is evaporateto form white colour of anhydrous copper sulphate.

                       Heat

CaSo4 . 5H2O Hydrated copper sulphate ..………..> CuSo4 Anhydrous Copper sulphate + 5H2O [ Goes Away]

  • Strongly heating of copper sulphate is turns white anhydrous copper sulphate because of loss of water of crystallisation.

(b) When a few drops of water is added to anhydrous copper sulphate it  form hydrated copper sulphate which is blue in colour.

Anhydrous copper sulphate turns blue on adding water.

 

41)

(a) Name two constituents of baking powder?

(b) How does baking powder differ from baking soda?

(c) Explain the action baking powder in the making of cake (or bread). Write equation of the reaction involved.

Ans : (a) In baking powder sodium hydrogen carbonate and Tartaric  acid this two constituents is present.

(b) In baking powder sodium hydrogen carbonate and Tartaric acid is present and in baking soda only sodium hydrogen carbonate is present.

Baking soda is single compound and baking powder is mixture of sodium hydrogen carbonate and  Tartaric acid. Hence it is differ from each other.

(c ) When a baking powder mixed with water in the process of baking cake , the baking soda ( sodium hydrogen carbonate) & water is reacts with Tartaric acid to form sodium ions and carbon dioxide gas is evolved.

NaHCO3 ­sodium Hydrogen Carbonate [Baking Soda] + H (Aq) Hydrogen ions ……> Na+ (Aq) Sodium ions + CO2 (g) + H2O Water

Formation of sodium tartrate salt & carbon dioxide gas is responsible for making soft and spongy  cake .sodium Tartrate smell is very pleasant . due to this pleasant smell the taste  of cake is good. The carbon dioxide gas is trapped in the wet dough and bubbles out slowly making the cake or bread to rise and become soft and spongy.

 

42)

(a) What is the chemical name of bleaching powder?

(b) What is the chemical formula of bleaching powder?

(c) What are the materials used for the preparation of bleaching powder?

(d) State one use of bleaching powder ( other than bleaching).

Ans :  (a) The chemical name of bleaching powder is calcium oxychloride.

(b) The chemical formula of bleaching powder is CaOCl2.

(c ) Calcium hydroxide (slacked lime ) and chlorine is used to make bleaching powder. When calcium hydroxide is react with chlorine gas to form calcium oxychloride and water.

Ca (OH)2 Calcium Hydroxide [Slacked lime] + Cl2 (Chlorine) ……> CaOCl2 + H2O

(d) in industry manufacturing of chloroform is carried out by using bleaching powder.

 

43)

What does soda acid type fire extinguisher contain ? How does it work ? Explain the working of a soda acid fire extinguisher with the help of a labelled diagram.

Ans : In soda acid type fire solution of sodium hydrogen carbonate & sulphuric acid is present

Working of soda acid fire :

Soda acid fire made up of sodium hydrogen carbonate and sulphuric acid .

Structure : in soda acid fire sodium hydrogen carbonate placed in lower portion of wash bottle  and dilute sulphuric acid is present in ignition tube. The Gas tube placed in solution of sulphuric acid .and nozzle is come out from the cap for the purpose of spreading of gas

Working : the knob of fire extinguisher on and sulphuric acid is mixed in sodium hydrogen carbonate and reaction is takes place between sulphuric acid and sodium hydrogen carbonate to form carbon dioxide gas . This gas is use to control fire

Carbon dioxide gas coming out due  to the pressure it forcefully . It is come with liquid drops .   this drops falls on burning substance . It form a safe jacket or blanket surrounding the burning substance . Due to this air supply is cut off . Because of  less air supply, burning is stop and fire get controlled.

 

  • Diagram of soda fire extinguisher

44)

(a) Name a sodium compound used for softening hard water.

(b) Which compound of calcium is used for disinfecting drinking water supply?

 (c) Name a metal compound which has detergent properties (cleansing properties ).

 (d) Name one compound calcium which is used for removing the colour a coloured cloth.

 (e) State a peculiar (or remarkable) property of plaster of Paris.

 (f) Name the substance obtained by the action of chlorine an solid (dry) slaked lime.

Ans :  (a) The sodium compound which is sodium carbonate is used for softening hard water.

(b) Calcium oxychloride [bleaching powder] is use for disinfecting drinking water supply.

(c ) Sodium carbonate is a metal compound which has detergent properties [ cleaning properties].

(d) Calcium oxychloride [bleaching powder] is used for removing coloured from a coloured clothes.

(e) the plaster of Parisshow property to   setting into a hard mass after  wetting with water

When water is added to plaster of Paris , itself  is to become a hard mass .in about half an hour . due to hydration setting of plaster of Paris is take place And to form  crystals of Gypsum . which set to form a hard solid mass.

CaSO4 . ½ H2O + 1½ H2O ……..> CaSO4 . 2H2O

(f) When a dry solid slaked lime is treated with chlorine to form calcium oxy chloride [ bleaching powder] with water.

Ca (OH)2 Calcium Hydroxide + Cl2 Chlorine ……….> CaOCl2 Calcium Oxychloride  + H2O Water

 

45)

(a) What is Gypsum ? What happens when gypsum is heated to 100C (373K) ?

(b) Name a sodium compound which is used for making borax and glass?

(c) Name the compound which is used in hospital for setting fractured bones.

(d) Which is real bleaching agent present in bleaching powder ?

Ans :  (a) Gypsum is a calcium sulphate dehydrate CaSO4.2H2O.  in Gypsum two  molecule of water of crystallisation is present.

  • When gypsum is heated to 1000C (373K) into form of a plaster of Paris Along with water molecule

  • The formula of plaster of Paris is also written as 2CaSO4.H2O so multiply all the equation by 2 and write again it.

(b)  Sodium carbonate [Na2CO3] is a sodium compound which is used for making borax and glass.

(c ) Plaster of Paris is used in hospitals for setting fractured bones .

(d) Chlorine is a real bleaching agent present in a bleaching powder.

The chlorine produced by the action of a dilute acid on bleaching powder . due to the oxidising property of  chlorine it is used for bleaching . some coloured substance is get colourless when oxidised by chlorine.

 

46) (a) What is “baking powder”? How does it make the cake soft and spongy?

(b) In addition to sodium hydrogencarbonate, baking powders contain a substance X. Name the substance X. What is the role of substance X in the baking powder?

Ans :  (a) Baking Powder : Baking powder is a mixture of sodium hydrogen carbonate [ Baking Soda] and mostly useful in   edible acid such as Tartaric acid .

In the process of baking cake , The baking powder is mixed with water . it  means that the sodium hydrogen carbonate reacts with water to from sodium Tartrate salt and carbon dioxide gas.

In this process carbon dioxide is collect in dough due to this bubbles form on the surface of cake .It is soft and spongy . on the other side the sodium tartrate salt have an pleasant smell because of  pleasant smell the taste of food is good.

 

(b) In addition of sodium hydrogen carbonate the  baking powder contain a substance X . The substance  X is Tartaric acid.

The role of tartaric acid is to give good and delicious taste to food . If the  sodium hydrogen carbonate is present then sodium carbonate is formed because of  action of heat during  baking process due to this sodium carbonate,  taste of food is bitter.

For a good taste, Tartaric acid is present in a baking powder along with sodium hydrogen carbonate.

 

47) State two uses each of the following Compound :

(a) Sodium hydroxide  (b) Chlorine   (c ) Hydrogen  (d) Hydrochloric acid

Ans :  (a) sodium hydroxide:

  • Artificial textile , fibres and rayon are made by using sodium hydroxide
  • In aluminium metal extraction process sodium hydroxide is used .sodium hydroxide is used to the purify bauxite ore to form pure aluminium metal
  • In metal oil refining process and production of dyes and bleaches sodium hydroxide is used .

(b)chlorine

*  Hydrochloric acid is made from chlorine .

* Formation of plastics ( polyvinyl chloride PVC ) , pesticides , dye stuff  are takes place using chlorine

*cleaning solvent trichloroethane is made by using  chlorine gas in laboratory.

(c ) hydrogen

  • Formation of ammonia fertiliser takes place by using hydrogen gas
  • In Production of methanol ( CH3 OH ) hydrogen is used
  • Hydrogenation of oil is due to hydrogen

(d) hydrochloric acid

* Mostly  Hydrochloric acid is used in medicine &cosmetics

* in textiles, dyeing tanning  industries hydrochloric acid is in most of the production process

*  in making plastics like Polyvinyl chloride [PVC] is takes place by using hydrochloric acid.

 

48) (a) What is the common name of the compound CaoCl2 ?

(b) Name the raw material used for the preparation of plaster of Paris.

(c) Which property of plaster of Paris is utilised is making casts for broken limbs in hospitals ?

(d) Explain why chlorine is used for sterilising drinking water supply.

Ans  (a) The common name of the compound CaOCl2 is bleaching powder.

(b) The raw material which is used to make plaster of Paris Gypsum [CaSO4.H2O].

(c) When a plaster of Paris is mixed with water , it is sets into a hard mass within half an hour. The setting of plaster of Paris is due to its hydration to form crystals of gypsum which sets to form a hard solid mass. Plaster of Paris form solid hard mass hence it is  utilised in making caste for broken limbs in hospitals.

(CaSO4)2.H2O + 1½H2O ………..> CaSo4 . 2H2O

(d) Chlorine is a disinfectant i.e. chlorine have tendency to kill the bacteria present in water And make it safe.

Due to this property chlorine is used for sterilizing drinking water supply.

 

49) 

(a) What happens when a concentrated solution of sodium chloride [brine ] is electrolysed ? Write the equation of the reaction involved

(b) Why is the electrolysis of a concentrated solution of sodium chloride know as chlor-alkali process?

 (c) Name three products of the chlor-alkali process. State two uses of each of these products.

Ans :  (a) When a concentrated solution of sodium chloride [Brine] is electrolysed , it decomposed to form sodium hydroxide. Chlorine and hydrogen

Electrolysis process means addition of water molecule .in the electrolysis of sodium chloride, The chlorine gas is produced at the anode .The hydrogen gas is produced at the cathode and sodium hydroxide solution produced near the cathode.

(b) The process electrolysis of the concentrated Solution Of sodium chloride is known as chlor-alkali process because through out the process  The chlorine gas and sodium hydroxide is produced .

chlor denoted that chlorine gas and  sodium hydroxide is denoted alkali nature

Hence it is called as chlor-alkali process.

( c) In the chlor- alkali process sodium hydroxide (common soda) ,  Chlorine gas and hydrogen gas is produced.

Uses of sodium hydroxide ( NaOH ):

  • Artificial textile , fibres and rayon’s are made by using sodium hydroxide
  • In aluminium metal extraction process sodium hydroxide is used.

It is use for the purification of bauxite ore to form pure aluminium metal

Uses of chlorine ( Cl 2 ):

  • Hydrochloric acid is made from chlorine .
  • Formation of plastics ( polyvinyl chloride PVC ) , pesticides , dye stuff are takes place using chlorine
  • cleaning solvent trichloroethane is formed by using chlorine gas in laboratory.

Uses of hydrogen

  • In Production of methanol ( CH3 OH ) hydrogen is used
  • In liquid form It is use as a fuel in rocket

 

50) (a) Describe how washing soda is produced starting from sodium chloride (common salt). Write equations of all the reactions involved.

 (b) State whether an aqueous solution of washing soda is acidic or alkaline? Give reason for your answer.

(c) What is meant by saying that washing soda has detergent properties?

 (d) Give two important uses of washing soda ( or sodium carbonate).

Ans: (a) Washing soda is produced by sodium chloride (common salt) in three steps, which is explain below:

  • First step: concentrated solution of sodium chloride [Brine] is reacted with carbon dioxide , ammonia along with water to form precipitated of sodium hydrogen carbonate and ammonium chloride Sodium hydrogen carbonate present as solid mass . It is separate out .

NaCl Sodium Chloride + NH3 Ammonia + H2O Water + CO2 Carbon dioxide ………> NaHCO3 Sodium Hydrogen Carbonate + NH4Cl Ammonium Chloride

  • Second step: slightly soluble sodium hydrogen carbonate is separated by using filtration  process and dried it. After drying it is heated due to heating,  it is  decomposed into sodium carbonate, carbon dioxide & water.

In this step anhydrous sodium carbonate [soda ash] is formed.

                             Heat

2NaHCO3 Sodium Hydrogen Carbonate ..……………> Na2Co3 + Co2 + H2O

 

  • Third step: Anhydrous sodium carbonate [soda ash] is mixed in water. It is completely dissolved & recrystallizedit, to form washing soda crystals .

By this three process washing soda is formed from sodium chloride.

Na2CO3 Sodium carbonate+ 10 H2O Water ………….> Na2Co3 . 10H2O Washing Soda Crystal 

 

(b) Aqueous solution of washing soda is alkaline in nature.

Because when washing soda is mixed with water to form sodium hydroxide and carbonic acid it means that it produce strong base and weak acid.

When strong base is produce solution is alkaline

also aqueous solution of washing soda shows changes red litmus paper to blue colour.

Hence the aqueous solution of washing soda is alkaline in nature.

 

(c) Washing soda have detergent or cleaning properties because washing soda transfer dirt and grease into water soluble molecules and remove it from clothes and make cloth clean .

 

(d) Uses of washing soda [sodium carbonate].

*  permanent hardness of water is easily remove by using washing soda

*  sodium compound like borax is produce by using washing soda

* in the glass manufacturing process sodium carbonates is use .

 

51) (a) What is bleaching powder ? How is bleaching powder prepared? Write chemical equation of the reaction involved in the preparation of bleaching powder.

(b) What happens when bleaching powder reacts with dilute sulphuric acid? Give equation of the reaction involved.

(c ) state two important uses of bleaching powder.

Ans : (a ) Bleaching powder : bleaching powder is a calcium oxy chloride.

Chemical formula of bleaching powder is CaOCl2.

Bleaching powder is also called as chlorine of lime.

Preparation of bleaching powder :

Bleaching powder is prepared from dry slacked lime and chlorine gas . When a gas is passed  over calcium hydroxide , it converted into calcium oxy chloride.

Ca (OH)2 Calcium Hydrogen + Cl2 Chlorine ………> CaoCl2 Calcium Oxy Chloride  + H2O Water

(b) When bleaching powder [ calcium oxy chloride] is react dilute sulphuric acid to form calcium sulphate, chlorine and water.

In this process all the chlorine molecules  is liberated .  it act as a bleaching agent.

CaoCl2 (Calcium oxy chloride) + H2So (Sulphuric acid) …….> CaSo4 (Calcium Sulphate) + Cl2 (Chlorine gas) + H2O (Water)

 

(c ) Uses of bleaching powder :

  • Bleaching powder is use to purify water .it act as a disinfectant agent
  • Bleaching powder is shows reduction hence it is use as oxidising agent in industry for manufacturing process

chloroform [CHCl3] is made up from bleaching powder

 

52) (a) What is plaster of Paris ? write the chemical formula of plaster of Paris.

(b) How is plaster of Paris prepared ? write chemical equation of the reaction involved.

(c ) Explain why plaster of Paris should be stored in moisture-proof container.

(d) State two important use of plaster of Paris .

Ans: (a) Plaster of Paris: Plaster of Paris is a calcium sulphate hemihydrates compound. Or it is calcium sulphate half – hydrate.

The name plaster of Paris is given because , it is made by heating Gypsum which was mainly found in Paris.

Plaster of Paris commonly known as P.O.P.

  • The chemical formula of plaster of Paris CaSO.1/2 H2O.
  • In plaster of Paris half molecules of water in crystallisation is present .

( b) Preparation of plaster of Paris :

Plaster of Paris prepared from gypsum . Gypsum is a calcium sulphate dehydrate.Chemical formula of gypsum is CaSO4.2 H2O. In gypsum 2 water molecule of crystallisation.

The Gypsum is heated at 100 0C or 373K temperature in a Klin . After Completion of heating plaster of Paris is formed .   three fourths of its water of crystallisation consumed to form hemihydrates or half hydrate plaster of Paris.

In the preparation of gypsum, heating should be carefully. If gypsum is heated above 100 0C it form burnt Plaster of Paris.

(c ) Plaster of Paris should be store on a moisture-proof containers because if the moisture is present in  a plaster of Paris,it  slow setting process  along with its hydration . due to the slow setting of plaster of Paris it become useless

Hence plaster of Paris should be stored in moisture-proof container . There is no moisture or water molecules is present and plaster of Paris becomes useful for long time.

(d) Uses of Plaster of Paris :

* most of the  toys, decorative materials. Cheap ornaments, cosmetics, Black- board and casts for statues are made up from plaster of Paris

*in chemistry laboratory air gaps is present in appratus , this gap is filled by using plaster of Paris

 

53)

(a) What is a salt? Give the names and formulae of any two salts. Also name the acids and bases from which these salts may be obtained.

(b) What is meant by `a family of salts’? Explain with examples.

(c ) What is meant by ‘hydrated’ and `anhydrous’ salts Explain with examples.

(d) write the names, formulae and colours of any two hydrated salts.

(e) What will be the colour of litmus in an aqueous solution of ammonium chloride salt ?

Ans :

  • Salt : salt is a compound formed from an acid by the replacement of the hydrogen in the acid by a metal.

Generally salt are formed when acid reacts with base.

  • Salts has two parents : an acid and a base.
  • The name of salts is derived from two parts.

First part of the salt name is derived from the name of base .

Second part of the name of salt comes from an name of acid.

  • Salt are ionic compound they contain positive charge ions and negative charge ions.

Example: 1) Sodium sulphate [ Na2SO4]:

sodium sulphate is formed by the reaction of sulphuric acid and sodium hydroxide.

In sodium sulphate — Acid part is sulphuric acid

— Base parts is sodium hydroxide.

2) Zinc sulphate[ZnSO4] :

Zinc sulphate is formed by the reaction of sulphuric acid [H2SO4] and zinc hydroxide Zn(OH)2 .

In zinc sulphate —–Acid part is —– Sulphuric acid

Base part is – zinc hydroxide.

  • The salts having the same positive ions or same negative ions are said to a family of salts.

Important family of salts :

Sodium salts, calcium salts, Magnesium salts, zinc salts, potassium salts, Aluminium salts, Copper salts, Ammonium salts, chloride salts, Sulphate salts , Nitrate Salts, carbonate salts, Acetate salts.

e.g: Sodium chloride [ NaCl] and potassium chloride ( KCl ). this two salts are belongs to the same family of salts. I.e.  `family of chloride salts’.

They are belongs to the same Family because they both contain the same negatively charged ions, Chloride ions (Cl-).

(c ) Hydrated salts :

  • It is a crystalline salts.
  • The salts in which water of crystallisation is present is called hydrated salts. It means that presence of water molecules is salts.

e.g :  Iron sulphate heptahydrate salt ( FeSO4.7H2O) .

in this salts 7 molecules of water of crystallisation is present.

  • Anhydrous salts :

After  heating salt  loss their water of crystallisation are called Anhydrous salt

Simply means that loss of water molecule from the salts.

e.g :  Iron sulphate dehydrate is heated and it loss 7 molecule of water of crystallisation to form anhydrous iron sulphate .

(d)  (1)  Sodium carbonate decahydrate .

Chemical formula of sodium carbonate decahydrate is  Na2CO3. 10 H2O.

  • * It is white in colour .

(2) Copper sulphate Pentahydrate

Chemical formula of copper sulphate Pentahydrate is CuSO4.5H2O.

  • It is blue in colour.

(e) In aqueous solution of Ammonium chloride salts. The blue litmus paper turns red in colours. Because ammonium chloride salts are formed by strong acid and weak base and it shows acidic nature.

Updated: August 28, 2021 — 3:22 pm

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