Test: Important Chemical Compounds - UPSC MCQ

PLASTER OF PARIS is a white or yellowish, finely divided, odorless powder consisting mostly or entirely of calcium sulfate hemihydrate, CaSO₄.1/2H₂O.

Washing soda is chemically sodium carbonate, which is a basic salt. When dilute HCl is added to washing soda, acid base neutralisation reaction takes place and sodium chloride is formed along with water and carbon dioxide. Following is the chemical equation for the reaction

 Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂

Hence, the correct answer is (b) carbon dioxide. 

Baking powder is a mixture of baking soda NaHCO₃,(sodium hydrogen carbonate)and a mild edible acid such as tartaric acid

Carbon dioxide is released when baking soda is added to cake and this makes the cake to rise making them soft and spongy.

Sodium acetate (CH₃COONa) is a salt in solid state and can't be regarded as an acid or base in anhydrous or molten form.
Although, being an ionic compound, sodium acetate dissociates in water to produce sodium ion Na+ and acetate ion CH₃COO^-. These ions react with water producing NaOH and CH₃COOH.
Now, as NaOH is a strong base and CH₃COOH is a weak acid, the resultant solution is basic in nature.
Hence, sodium acetate is basic in aqueous medium.

Plaster of Paris i.e, CaSO₄.1/2H₂O is used by doctors as plaster for supporting fractured bones in the right position.

Correct option is B. Baking soda solution 

Sodium hydrogen carbonate (also known as sodium bicarbonate or bicarbonate of soda) has the chemical formula NaHCO₃ . When it is heated above about 80°C it begins to break down, forming sodium carbonate, water and carbon dioxide.

Gypsum is calcium sulphate dihydrate. The chemical formula of gypsum is CaSO₄·2H₂O
Plaster of paris is prepared by heating gypsum to a temperature of 373K.When gypsum is heated to a temperature of 373k ,It loses three-Fourths of its water of crystallisation and forms plaster of paris.

The excess of acid in the stomach causes acidity. As NaHCO₃ is alkaline in nature, it neutralizes the excess acid and relieves discomfort. Hence it is an essential ingredient in antacids. Following equation explains its reaction with HCl 

 NaHCO₃ + HCl → NaCl + H₂O + CO₂↑