Mind Map on Ch 2 Acids, Bases and Salts Class 10​

Reaction of acid with metal:

  • When metal reacts with acid then in that reaction metal displaces hydrogen atom from the acid forms the hydrogen gas and salt.
  • That means, Acid + Metal —> salt + hydrogen gas

For example:

2NaOH(aq) + Zn(s)—-> Na2ZnO2(s) + H2(g)

Reaction of metal carbonates and hydrogen carbonates with acids:

  • All the metal carbonates and hydrogen carbonates react with the acids and forms the corresponding salts, carbon dioxide and water.
  • It can be summarised as

Metal carbonates/ metal hydrogen carbonates + acid —> salt + carbon dioxide + water

For example:

Na2CO3(s) + 2HCl(aq) —> 2NaCl(aq) + H2O(l) + CO2(g)

  • When sodium carbonate reacts with hydrochloric acid it forms the salt as sodium chloride and releases carbon dioxide and water.
  • Similarly, when sodium bicarbonate reacts with hydrochloric acid it forms the salt Black with the release of water and carbon dioxide as given below.

NaHCO3(s) + HCl(aq) —–> NaCl(aq) + H2O(l)+ CO2(g)

Reaction of acids and bases with each other:

  • When acid reacts with the base it forms the salt and water. Such reaction is called as neutralisation reaction. In general neutralisation reaction can be written as

Base + Acid —> Salt + Water

For example:

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

Reaction of metallic oxides with acids:

  • When metal oxides react with the acid, they also form the salt and water. The general reaction of metal oxide with acid can be written as

Metal oxide + Acid —> Salt + water

Properties of acids:

  • Acids contains H+ ions as cations.
  • Like in HCl, H+ is cation and Cl is anion and hence HCl acts as an acid.
  • HNO3 also acts as acid as it contains H+ ions as cations and NO3 ions as anions.
  • Similarly, H2SO4 and CH3COOH are also the acids as they contain H+ ions as cations.
  • H+(aq) ions are mainly responsible for the acidic nature of the acids.

Reaction of acid or base in water solution:

  • The H+ ion separation from acid HCl is possible in presence of water only.

Thus, HCl + H2O —> H3O++ Cl

  • Hydrogen ions may exist as H+(aq) or hydronium ions H3O+.

Hence, H+ + H2O —-> H3O+

  • Thus, we can say that when acids dissolved in water, they produce H+
  • But when bases react with water, they produce OH- ions mainly.

For example:

NaOH(s) —-> Na+(aq) + OH(aq)

KOH(s) —–> K+(aq) + OH(aq)

Mg(OH)2 —-> Mg2+(aq) + 2OH(aq)

  • Thus, bases generate hydroxide ions that means OH- ions on dissolution with water.
  • The bases which are soluble in water are called as alkalis.
  • The dissolution of acid or base in water is highly exothermic reaction so while adding acid or base with water we have to stir constantly to avoid heat splash. More heat and sometimes burning is also possible in case of concentrated acids when added to water.
  • When we add the acid or base to water there will be continuous decrease in the H3O+ or OH- ions per unit volume takes place. This process is called as dilution and the acid or base which is added to water is said to be diluted.

pH scale:

  • The scale which is used for measuring hydrogen ion concentration in the solution is called as pH scale. The pH scale has numbers from 0 to 14 only. The number 0 on scale indicates very acidic nature while the number 14 on pH scale indicates very basic nature.
  • Higher is the hydronium ion concentration lower will be the pH value of the solution. The solution is said to be neutral when it has pH value as 7. And if the pH value is less than 7 it means the solution is acidic.
  • As we go on the pH scale from 7 to 14 the OH- ion concentration increases in the solution which means strength of the alkali increases. Hence, solution with pH greater than 7 are more basic in nature.

For example:

  • The pure water and blood have pH value 7.4
  • Gastric juice is acidic in nature and has pH value 1.2
  • Lemon juice is also acidic in nature and has pH value 2.2
  • Milk of magnesia is basic in nature and has pH value 10.
  • Sodium hydroxide solution has pH value 14.

Weak acids and strong acids:

  • Those acids which gives more H+ ion is called as strong acids. And those acids which gives less H+ ions are called as weak acids.

Weak bases and strong bases:

  • The bases which give more OH- ions are called as strong bases and the bases which gives less OH- ions are called as weak bases.

Importance of pH in everyday life:

In plants and animals:

  • Our body is working within the pH range of about 7 to 7.8. The water of acid rain is having pH less than 5.6. As this low pH acidic water enters the river water then the pH of river water also gets decreased. So, due to decrease in pH value of such water life of aquatic animals is in danger.
  • As animals requires maintained pH value , in similar way plants also requires specific pH range for their healthy growth.
  • In our stomach hydrochloric acid is produced which helps in digesting the food without giving any harm to stomach. When we feel pain in our stomach that means there will be more acid will be produced.
  • Also, tooth decay starts when pH of mouth is lower than 5.5. Tooth is made from the substance which is hardest in the body. Toothpaste is made generally basic which reacts with the bacteria produced in mouth which are acidic and neutralises all to prevent the tooth decay.

For example:

Natural source

Acid
Orange

Citric acid

Tomato

Oxalic acid
Sour milk

Lactic acid

Vinegar

Acetic acid
Tamarind

Tartaric acid

Lemon

Citric acid

Salts, properties and reaction:

  • Salts are the neutral in nature which are having pH value as 7. While salts of string acid and weak base are acidic in nature having pH value less than 7.
  • And the salts of string base of weak acids are acidic in nature and are having pH value greater than 7.
  • Common salt is the raw material for sodium hydroxide, baking soda, washing soda and bleaching powder.
  • Sodium hydroxide is formed when salt and water react together as given in the following chemical reaction.

2NaCl(aq) + 2H2O(l) —–> 2NaOH(aq) + Cl2(g) + H2(g)

This process of formation of sodium hydroxide is called as chlor-alkali process.

Bleaching powder:

  • When chlorine is on action with dry slaked lime bleaching powder is produced as given in the following chemical reaction.

Ca(OH)2+ Cl2 —–> CaOCl2 + H2O

  • Bleaching powder is used for bleaching cotton, wood pulp in paper factories, washed clothe in laundry and linen in textile industry.
  • It is also used as an oxidizing agent.
  • While making drink water free from germs bleaching powder is used.

Baking soda:

  • Baking soda is used in kitchen to make food crispy. Also, it used to cook food fast. NaHCO3 named as sodium hydrogen carbonates is called as baking soda.
  • It can be produced as given by the following chemical reaction.

NaCl + H2O + CO2 + NH3 —–> NH4Cl + NaOHCO3

Uses:

  • Baking powder is made from baking soda.
  • It is used as ingredients in antacids. And as it is alkaline it neutralises the excess acid produced in stomach and gives relief to us.
  • In soda acid fire extinguishers baking soda is used.

Washing soda:

  • Washing soda is having chemical composition as Na2CO310H2O.
  • It can be prepared as given by the following chemical reaction.

Na2CO3 + 10H2O —-> Na2CO3•10H2O

Uses of washing soda:

  • It is used in glass, soap and in paper industries also.
  • In manufacturing sodium compounds like borax washing soda is used.
  • For domestic purpose washing soda is used as cleaning agent also.
  • The hardness of water is removed permanently by using washing soda only.

Plaster of Paris (POP):

  • When gypsum is heated at 373K temperature, it loses the water molecule and forms the calcium sulphate hemihydrate i.e.CaSO41/2H2O. This compound formed is called as plaster of Paris.
  • Doctors mostly use plaster of Paris for supporting the fractures in bones to the right position.
  • POP is the white powder and when is mixed with water again produces gypsum which is a hard solid mass.
Updated: April 14, 2022 — 12:15 pm

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