NIOS Class 10 Science & Technology Chapter 8 Solution

NIOS Class 10 Science & Technology Chapter 8 Solution – Acids, Bases And Salts

NIOS Class 10 Science & Technology Solution Chapter 8 Acids, Bases And Salts. NIOS Class 10 Science & Technology Chapter 8 Question Answers Download PDF. NIOS Class 10 Science Notes.

NIOS Class 10 Science & Technology Chapter 8 Solution

Board NIOS
Class 10th  (Secondary)
Subject Science and Technology (212)
Topic Question Answer, Solution, Notes



(Acids, Bases And Salts)



1) Put the following substances in acid or base bottle.

(a) Milk of magnesia

(b) gastric juice in humans

(c) soft drinks

(d) lime water

(e) vinegar

(f) soap.

Ans: – In acid bottle the substance will be: – gastric juice in human, vinegar, soft drinks.

In base bottle: – Milk of magnesia, lime water, soap.


2) What will happen if you add a drop of the following on a cut unripe apple, curd, causting soda solution and soap solution.

(i) phenolphthalein

(ii) litmus.

Ans: – Phenolphthaleinis Colourless on unripe but pink in caustic soda and soap.

Litmus turns red on unripe apple but become blue in soda and soap solution.



1)Name the substances in which the following acids are present:

(a) Ethanoic acid (b) Tartaric acid.

Ans: – Option (a).


2)Which of these acids would be partially dissociated in their aqueous solution?

(a) HBr (b) HCN

(c) HNO3 (d) C2H5COOH.

Ans: –  HCN and HNO3.


3)An acid reacts with a substance X with liberation of a gas which burns with a‘pop’ sound when a burning match stick is brought near it. What is the natureof X?

Ans: – From the upper description it is clear that the upper substance must be a metal.


4) An acid reacts with a substance Z with the liberation of CO2 gas. What can be the nature of Z?

Ans: – The nature of the z is base and this base will be carbonate or NaHCO3 which after reaction with the acid will produce the carbon dioxide gas.


5) Which of the following oxides will react with a base?

(a) CaO (b) SO2.

Ans: – The oxide which reacted with the base is SO2.



1)Why does the colour of dry blue litmus paper remains unchanged even whenit is brought in contact with HCl gas?

Ans: – The colour of blue litmus papers remains unchanged if there is no such acid or base. In HCl there is no free electron present in that so the colour will not change.


2)How does water help in dissociation of acids and bases?

Ans: – The water molecules are bonded with the ionic and the covalent bond so there will be acids and bases ions and this element will be H (+) and OH (-).


3)Identify the nature of the following aqueous solutions (whether acidic, basic orneutral)

(a) Solution A: [H+] < [OH–] (Basic)

(b) Solution B: [H+] > [OH–](Ionic)

(c) Solution C: [H+] = [OH–](Neutral).



1)pOH of a solution is 5.2. What is its pH. Comment on the nature (acidic, basicor neutral) of this solution.

Ans: –   As we know that, pH + pOH = 14

So, PH = 14 – pOH

= 14 – 5.2

= 8.8

As pH > 7.0, so this is basic in nature.


2) pH of a solution is 9. What is the concentration of H+ ions in it?

Ans: – As we know, pH = –log[H+]

And, pH = 9

Then, log[H+] = –9

or [H+] = 10–9 mol L–1.


3) What is the nature (whether acidic, basic or neutral) of the following solutions?

(a) Solution A: pH = pOH (Its neutral)

(b) Solution B: pH >pOH (Its acidic)

(c) Solution C: pH <pOH (Its basic).



1) Identify acid radical and basic radical in CaSO4.

Ans: – In CaSO4 the basic radical is Ca (+2) and the SO4(-2) is acidic radical.


2)CuSO4 was prepared by reacting an acid and a base. Identify the acid and thebase that must have been used in this reaction.

Ans: – Acid is H2SO4 with the acid radical SO4(2–)

Baseis Cu (OH)2 with the basic radical Cu (2+).


3)Which one of the following is the correct formula of plaster of paris?

CaSO4.H2O or 2CaSO4.H2O.

Ans: – The formula of plaster of paris is CuSO4.1/2H2O or 2CuSO4.H2O.



A) Objective Type Questions

I) Mark the correct choice


1)Lemon juice contains

(a) tartaric acid (b) ascorbic acid

(c) acetic acid (d) lactic acid.

Ans: – Option (a).


2)Aqueous solutions of acids conduct electricity. This shows that

(a) They contain H+ ions

(b) They contain OH– ion

(c) They contain cations and anions

(d) They contain both H+ and OH– ions.

Ans: – Option (c).


3)Which of the following is not a strong acid?

(a) HCl (b) HBr

(c) HI (d) HF.

Ans: – Options (d).


4)Self dissociation of water produces

(a) a large number of H+ ions

(b) a large number of OH– ions

(c) H+ and OH– ions in equal numbers

(d) H+ and OH– ions in unequal numbers

Ans: – Option (c).


5)In any aqueous basic solution

(a) [H+] > [OH–] (b) [H+] < [OH–]

(c) [H+] = [OH–] (d) [H+] = 0.

Ans: – Option (b).


6)In an aqueous solution of HCl which of the following species is not present?

(a) H+ (b) OH–

(c) HCl (d) Cl-.

Ans: – Option (b).


7) Which of the following is not a raw material for manufacturing washing soda?

(a) Lime stone (b) Ammonia

(c) Slaked lime (d) Sodium chloride.

Ans: – Option (b).


Mark the following statements as true (T) or false (F):

1)Acids furnish H+ ions only in the presence of water. (True)

2)Lime water turns blue litmus red. (False)

3)HF is a strong acid. (False)

4) H2 gas is produced when acids react with metal oxides. (True)

5) Corrosive action of acids is due to H+ ions present in them. (True)

6)When the pH of the rain water become more than 5.6 it is called acid rain. (True)


7)Aqueous solutions of all the salts are neutral in nature i.e., neither acidic nor basic in nature. (False).

III. Fill in the blanks

1) Acid’s taste ……..sour………….. while bases taste …….. biter…………..


2) Milk of magnesia turns ……. blue…………… litmus ……. yellow……………


3) One mole of sulphuric acid would furnish ……..2………….. mole/s of H+ ions and

…….1……….. moles of SO4(2–) ions.


4) ……..H2………….. gas is produced when acids react with metal hydrogen carbonates.


5)Lime water turns milky on passing CO2 gas due to the formation of……….OH- ions…………


6)The reaction between an acid and a base is known as ……….neutralize reaction…………


7) Bee sting injects ……..formic………….. acid which causes severe pain and burning sensation.


8)In NH4NO3 the acid radical is ……NH4(+) ……………. and the basic radical is……NO3(-) ………


9) Chemically baking soda is ……NaHCO3…………….


Descriptive Questions

1)What is an acid?

Ans: – Acid is substance which gave H(+) ions in the solution.


2)Give two examples of acids found in food articles.

Ans: – In lemon we found citric acid and in milk we find lactic acid.


3)What is a base?

Ans: – The base is substance which gave the hydroxyl ions in the solution after dissolving.


4)Give two examples of bases.

Ans: – Sodium hydroxide is working as base and the lime water is the example of base.


5)What are indicators?

Ans: – The indicator is present in every solution which indicates about the nature of the solution whether it is basic or acidic medium or not.


6) What is the colour of methyl orange indicator in (i) acidic medium and (ii) basic medium.

Ans: – In acidic medium the colour of methyl orange is red and in basic medium the colour of it is yellow.


7) Why do solutions of acids and bases conduct electricity?

Ans: – The solution of acids and basic conduct electricity as this indicator bear the ion like hydrogen or hydroxyl which helps to transfer electricity.


8)Differentiate between strong and weak acids and give one example of each.

Ans: –

Strong acid

Weak base

H (+) Ions are present. OH (-) are present in it.


9)Write down the reaction between zinc and sulphuric acid.

Ans: – Zn + H2SO4 à ZnSO4 + H2.


10) Which gas is evolved when an acid reacts with metal carbonates? Which other category of compounds would produce the same gas on reacting with acids?

Ans: – When the acid reacts with the metal carbonate then the carbon dioxide gas will be evolved after this reaction.

The same gas when react with the acid then the carbonate form of the material will be produced and the hydrogen gas will be evolved.


11)What type of oxides react with acids? Give one examples of this type of oxide and write down the balanced equation for the reaction.

Ans: – The oxide is metal oxide.

The remaining reaction is,

ZnO2 + 4HCl —–> 2ZnCl2 +  2H2O.


12) What is the name given to the reaction between an acid and a base? What are the products formed in such reactions?

Ans: – If an acid and base react with each other then this reaction is known as neutralize reaction.

Example: – NaOH + HCl —> NaCl + H2O.


13)“Corrosive action of acids is not related to their strength”. Justify this statement.

Ans: – The corrosive action of acids is not related to their strength – If we talked about this reaction then we will see that the surface of the body is affected by the moisture present in the air which is the action of hydrolysis or water.


14) Give one example each of the following (i) a strong base (ii) a weak base.

Ans: – Strong acid: – NaCl and weak base: – NH4OH.


15) List three categories of substances that can react with a base. Give one example of each and write the chemical reaction involved in each case.

Ans: – NH4OH + HCl —-> NH4Cl + H2O.

2NaOH + CO2 —-> Na2CO3 + H2.



What happens when a dry strip of each of red litmus paper and blue litmus paper is brought in contact with HCl gas? In which case a change would be observed if the strips are moistened and then brought in contact with HCl gas and what would be the change?

Ans: – The dry cheap or blue litmus papers when will cake in contact with the hydrochloride acid then we will see its colour become red as the H(+) present in HCl turns to this change.

If this makes moisture then we will see if will act as a base so in that case the colour of this in contact with the hydrogen chloride make this yellow in colour.


17) A small palette of NaOH is kept on dry red litmus paper. Initially, no changeis observed but after some time its colour starts changing to blue around theplace where the palette of NaOH is kept. Explain these observations.

Ans: – As we all know that the litmus colour changes when it makes contact with the acidic or basic medium. In this case this red litmus changes it colour to the blue as this indicator is basic in nature.


18) How does water help in dissociation of acids and bases? Explain.

Ans: – There are hydrogen ion or H (+) and the hydroxyl ions (OH-) present in the water which react with the acid and base and makes the compound of oxide and produced the hydrogen gas.


19)What is ‘self dissociation of water’? Name the resulting species and give their concentrations at 25°C.

Ans: – The water is dissociated into the hydrogen and hydroxyl ions this phenomenon of water is known as the self-dissociation of water.


20)What is ionic product constant of water? Give its value at 25°C. Will the value change if an acid, base or a salt is dissolved in water?

Ans: – The ionic product constant express by the formula,

K(w)=[H3O+][OH-] , at 25degree Celsius value is 1*10-14mole 2 /l-2.


21)Give the relationships between the concentrations of hydrogen ions and hydroxyl ions in (i) pure water (ii) a neutral solution (iii) an acidic solution and (iv) a basic solution.

Ans: – In pure water the hydrogen and hydroxyl ions concentration are less amount.

In the neutral solution the concentration of hydrogen and the hydroxyl ions are same.

An acidic solution has the greater number of hydrogen ions than the hydroxyl ions.

In basic medium the hydroxyl ions concentration is more than the hydrogen ions.


22)What is pH? What happens to the pH if the hydroxyl ion concentration in the solution increases?

Ans: – The pH is the logarithmic value of concentration of hydrogen ions in a solution. If the PH value is increasing then we can say that that the concentration of hydrogen in that solution is increasing.


23) Predict whether a given aqueous solution is acidic, basic or neutral if its pH is

(a) 7.0, (b) 11.9 and (c) 3.2.

Ans: – pH value is 7 then this medium is neutral, pH value is 11.9 then it is basic and if the pH value is 3.2 then this medium is acidic in nature.


24)Calculate the pH of 1.0 ×10–4 molar solution of HNO3.

Ans: – pH=-log(H+).

Or, pH= -log (10^-4).

Or, pH=4.


25)What is the pH of 1.0 × 10–5 molar solution of KOH?

Ans: – pH=-log(H+).

Or, pH= -log (10^-5).

Or, pH=5.


26)What is the pH of 1.0 × 10–2 mol L–1 solution of NaCl?

Ans: – pH=-log(H+).

Or, pH=-log (10^-2).

Or, pH=2.


27)What do you understand by the term ‘universal indicator’?

Ans: – The indicator is nothing but the pH value of different object which tells us the nature of the substance is acidic or basic.


28) What is acid rain?

Ans: – Acid is the mixture of water and the toxic gas present in the air. It affects the monument or the marbles present in open area.

H2O + SO2 —-> H2SO4


29) What is the importance of pH for humans and animals, and our digestive system?

Ans: – He pH is very important for the digestion if the food present in our body as this food after the reaction with the basic substance which has more pH value than the minimise the acidity in our body.


30) Which chemical causes pain and burning sensation when somebody accidentally touches ‘nettle plant’?

Ans: – Histamine Acetylcholine is used for the pain and the burning sensation when somebody accidentally touches nettle plant.


31)What is a salt? Give two examples.

Ans: – The reaction between the acid and the bas in a reaction make the product salt and water.

Example: –

NaOH + HCl —-> NaCl + H2O.


32) How are salts obtained from an acid? Mention four types of substances that can be used for it.

Ans: – The reaction of acid with the basic substance makes the salt. For example, various acid or basic substance like NaOH, HC, MgO, CaO, NH4Cl etc.


33)Give chemical formula of (i) baking soda and (ii) washing soda.

Ans: – Baking soda: – NaHCO3.

Washing soda: – Na2CO3.


34) List the raw materials required for the manufacture of baking soda and describe the process with the help of suitable chemical equations.

Ans: –

The raw materials required to manufacture washing soda, Lime stone, Sodium chloride (NaCl) in the form of brine, Ammonia (NH3)

CaCO3(s) ⎯→ CaO(s) + CO2(g)↑

NaCl(aq) + CO2(g) + NH3(g) + H2O(l) ⎯→ NaHCO3(s)↓ + NH4Cl(aq)

2NaHCO3⎯⎯→ Na2CO3 + H2O + CO2↑


35)Distinguish between baking powder and baking soda. Why is baking powder preferred for making cakes?

Ans: – Baking powder is manufacturers by the uses of tartaric acid and the baking soda and baking soda is made from the reaction between ammonia, carbon dioxide, water.

2NaHCO3⎯⎯→ Na2CO3 + H2O + CO2↑

This cO2 emission makes the cake soft.


36)Give any two uses of baking soda.

Ans: – Baking soda is used for the making of bread, this also used for the making of baking powder.


37) What is washing soda? Give its chemical formula. How is it manufactured by Solvay’s method?

Ans: – Washing soda is used for the clearing of dust particles in clothes.

Chemical formula according to Solvay’s method,

2NaHCO3⎯→ Na2CO3 + H2O + CO2

Na2CO3 + 10H2O ⎯→ Na2CO3.10H2O.


38)Give two uses of washing soda.

Ans: – The uses of washing soda-

  • As cleaning regent.
  • Remove the hardness of water.


39) What is the chemical formula of ‘plaster of paris’? How is it manufactured? What precaution is taken during its manufacture?

Ans: – 2CaSO4.H2O or CaSO4.1/2H2O is the chemical formula of plaster of paris.

Manufacture of plaster of paris.

Raw material: –

Gypsum or CaSO4.2H2O

CaSO4.2H2O ⎯⎯⎯⎯⎯→ CaSO4.1/2H2O + 3/2H2O.


40) List any four uses of ‘plaster of paris’.

Ans: – Uses of plaster of paris: –

  • For making of walls and ceiling smooth.
  • For the decorative designs on ceilings, walls and pillars.
  • For making ‘chalk’ for writing on blackboard.
  • Making the fire proof materials.


41) What is bleaching? Chemically, what is bleaching powder? Give its any four uses.

Ans: – Bleaching powder is used for the disinfectant.

Its chemical name is calcium chloro hypochlorite.

Uses of bleaching powder is,

  • Textile industry for bleaching of cotton and linen.
  • paper industry for wood pulp bleaching.
  • Make the wool unshrinkable.
  • Used as disinfectant.


42) List the raw materials required and the method of manufacture of bleaching powder. Write the equation for the reaction involved.

Ans: – The raw material is, Slaked lime, Ca (OH)2 and Chlorine gas, Cl2.

Chemical reaction: – Ca (OH)2 + Cl2 ⎯→ CaOCl2 + H2O

Updated: February 21, 2022 — 12:37 pm

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