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ICSE Class 10 Chemistry Question 15 of 63

Study of Compounds — Nitric Acid — Question 10

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Question

Question 5d

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.

Answer

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 →>200°C\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.