Give reason for the following: Nitric acid not used for the preparation of hydrogen gas?
Answer
Hydrogen cannot be prepared by the action of nitric acid on metals because it also releases nitrous oxide and nitric oxide and oxides the hydrogen to form water.
Give reason for the following : Though hydrogen is lighter than air it cannot be collected by downward displacement of air.
Answer
Since hydrogen is lighter than air. it is possible to collect the gas by downward displacement of air. But it is not safe to do so since a mixture of hydrogen and air can lead to an explosion.
Redox reactions are those in which reduction and oxidation both takes place simultaneously i.e. one substance is reduced while the other gets oxidised.