State whether a sample of each of the following would increase or decrease in mass if exposed to air.

(a) Solid NaOH

(b) Solid CaCl₂

(c) Solid Na₂CO₃.10H₂O

(d) Conc. Sulphuric acid

(e) Iron (III) Chloride

(a) Why does common salt get wet during the rainy season?

(b) How can this impurity be removed?

(c) Name a substance which changes the blue colour of copper sulphate crystals to white.

(d) Name two crystalline substances which do not contain water of crystallisation.

State the change noticed when blue litmus and red litmus are introduced in the following solutions:

(a) Na₂CO₃ solution

(b) NaCl solution

(c) NH₄NO₃ solution

(d) MgCl₂ Solution

The acid which contains four hydrogen atoms is :

1. Formic acid
2. Sulphuric acid
3. Nitric acid
4. Acetic acid