Question

Consider the following substances :
NaCl, Ca(OH)2, NaHCO3, NH3, Na2CO3, H2O, Cl2, CO2, CaSO4.2H2O, 2CaSO4.H2O, CaOCl2
(a) Which two substances combine to form bleaching powder ?
(b) Which four substances are utilised in the production of washing soda ?
(c) Which compound represents plaster of Paris ?
(d) Which compound is a part of baking powder ?
(e) Which compound is used as an antacid ?

Lakhmir Singh Chemistry Class 10

Answer 1

Explanation:

A) Ca(OH)2 combines with Cl2 to give bleaching powder (CaOCl2 ).

The chemical reaction involved is as follows.

2Ca(OH)2 + CaCl2 → CaOCl2 + 2H2O

b) NaCl, NH3, H2O, CO2 are utilised in the production of washing soda.

The chemical reaction involved can be shown in three steps:

i) Production of sodium hydrogen carbonate:

NaCl + NH3 + H2O + CO2 → NaHCO3 +NH4Cl

ii) Production of anhydrous sodium carbonate upon heating sodium hydrogen carbonate:

2NaHCO3 → Na2CO3 + CO2 + H2O

iii) Production of hydrated sodium carbonate when anhydrous sodium carbonate is dissolved in water:

Na2CO3 + 10H2O → Na2CO3.10H2O

c) 2CaSO4.H2O represents plaster of Paris as its chemical formula is CaSO4.1/2H2O.

d) NaHCO3 is part of baking powder, as baking powder is a mixture of NaHCO3 and tartaric acid.

e) NaHCO3 is used as an antacid, as it is alkaline, thus it neutralises excess acid in the stomach.