i. Identify the acid and the base whose combination forms the common salt that you use in your food. Write the formula and chemical name of this salt. Name the source from where it is obtained.
ii. What is rock salt? Mention its colour and the reason due to which it has this colour.
iii. What happens when electricity is passed through brine? Write the chemical equation for it.
OR
i. Write the chemical name and chemical formula of washing soda.
ii. How is it obtained from sodium chloride? Give equations of the reactions.
iii. Why it is called a basic salt? Give its any one use.
(i) The acid is Hydrochloric acid (HCl), and the base is Sodium Chloride (NaOH) which will form Sodium Chloride (NaCl) i.e. common salt.
HCl + NaOH → NaCl + H2O
It is found naturally in large amounts in sea water.
(ii) Deposits of solid salt found in huge amount in different areas. These large crystals are called rock salt. And rock salt is brown in colour due to impurities.
(iii) When electricity is passed through brine, then sodium hydroxide (NaOH) is formed with the liberation of Hydrogen (H2) gas at cathode and Chlorine gas (Cl2) at the anode.
NaCl + H2O + Electricity → NaOH + H2 + Cl2
OR
(i) The chemical name of washing soda is Sodium carbonate decahydrate and its chemical formula is Na2CO3.10H2O.
(ii) (a) First sodium hydrogen carbonate prepared from sodium chloride by reaction of ammonia and carbon dioxide.
NaCl + NH3 + CO2 + H2O → NaHCO3 + NH4Cl
(b) And then sodium carbonate is obtained by heating sodium hydrogen carbonate.
NaHCO3→ Na2CO3 + CO2 + H2O
(c) Recrystallization of sodium carbonate gives washing soda.
Na2CO3 + 10H2O → Na2CO3.10H2O
(iii) It is basic salt because it is the salt of strong base and weak acid. It is used as cleaning agent.