Question

Consider the following substances:
NaCl, Ca(OH)₂, NaHCO₃, NH₃, Na₂CO₃, H₂O, Cl₂, CO₂, CaSO₄.2H₂O, 2CaSO₄.H₂O, CaOCl₂
(a) Which two substance 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?

Answer 1

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.