In the Contact process
Give a reason why - vanadium pentoxide is preferred to platinum during the catalytic oxidation of sulphur dioxide.

In the Contact process State the conditions i.e catalyst promoter , temperature and pressure in the catalytic oxidation of sulphur dioxide to sulphur trioxide in the Contact tower . Give a balanced equation for the same .

Give reasons for the observation seen during catalytic oxidation of ammonia.

In the Contact process Give a reason why the catalyst mass is heated electrically - only initially .

Give reason : A graphite anode is preferred to other inert electrodes during electrolysis of fused lead bromide.

In the Contact process State why the above catalytic oxidation reaction supplies energy .

The bleaching action of chlorine is permanent, whereas the bleaching action and sulphur dioxide is temporary. In this context : (i) Give a reason, why chlorine is not used to bleach silk. (ii) State similarity in the use of sulphur dioxide and chlorine as bleaching agents. (iii) Explain the bleaching action of sulphur dioxide with the help of chemical equations. (iv) Why is bleaching by sulphur dioxide only temporary?

Give reasons why? Direct current should be used during electroplating.

Why heating of catalyst is discontinued the moment the oxidation of sulphur dioxide takes place ?

In the stages involved in the extraction of metals in general - give reasons for following Coke is not preferred as a reducing agent in the reduction of the oxide of mercury to its metal, but is preferred in the reduction of the oxide of zinc to its metal.

In the Contact process state why sulphur trioxide vapours are absorbed in concentrated sulphuric acid and not in water to obtain sulphuric acid .