In which of the following substances will there be :

(a) increase in mass

(b) decrease in mass

(c) no change in mass when they are exposed to air?

1. Sodium chloride
2. Iron
3. Conc. sulphuric acid
4. Table salt
5. Sodium carbonate crystals

State the methods by which hydrated salts can be made anhydrous?

Water acts as a universal solvent because:

1. It is an organic compound
2. It is polar and has a high dielectric constant.
3. It is liquid at room temperature.
4. It boils at 100°C

Permanent hardness of water is removed by:

1. Adding calcium sulphate
2. Boiling with potassium chloride
3. Boiling
4. Adding sodium carbonate