Give reasons for the following:

In the laboratory preparation of nitric acid, the mixture of concentrated sulphuric acid and sodium nitrate should not be heated very strongly above 200°C.

The temperature of the reaction should not increase above 200°C, because sodium sulphate formed at higher temperature, forms a hard crust which sticks to the walls of the retort and is difficult to remove, although the yield of nitric acid is higher.

2NaNO₃ + H₂SO₄ $\xrightarrow{\gt 200 \degree\text{C}}$ Na₂SO₄ + 2HNO₃

The higher temperature

• may damage the glass apparatus.
• decomposition of nitric acid can also occur.
• wastage of fuel.