Write the reaction that occurs between:

• Magnesium oxide and water.

Write the reaction that occurs between:

• Calcium oxide and water.

All the soluble solid impurities settle down at the bottom of the sedimentation tank.

Sodium and magnesium salts make the water hard.

Hard water is fit for washing.

Sugar is solute in sugar solution.

The molecular formula of washing soda is ${\mathrm{Na}}_2{\mathrm{CO}}_3$.

Give reasons for the following.

• Seawater is saline.

Give reasons for the following:

• Water is called a universal solvent.