The reaction is exothermic and therefore, according to Le Chatelier's principle, it should be favoured by low temperature. However, the reaction should be carried out at an optimum temperature of about 750 K and not at 350 K. This is because the collision frequency of the reactant molecules decreases with decrease in temperature. As a result, the rate of reaction would decrease at a lower temperature. Consequently, at low temperature, the yield of the product will be less. Hence, the reaction should be carried out at about 750 K.

Nitrogen fertilisers are very useful for the growth of plants because these provide essential plant nutrients to the soil. However, these should not be used in excessive quantities. The excessive use of fertilisers has many disadvantages also. Some of these are: 
(i) The excessive use of nitrogenous fertilisers concentrates nitrates in the soil and water. Nitrate rich water is unfit for drinking. When this water is carried off into surface water bodies such as rivers, lakes and ponds, it proliferates the growth of algae. These algae consume dissolved oxygen from water and therefore, decrease the oxygen content in water leading to the death of useful aquatic life such as fish. Such an increase in growth of algae in rivers, lakes, ponds etc. resulting in the reduction of oxygen content in water is called eutrophication. Eutrophication destroys the life-supporting environment in rivers, lakes and ponds.
(ii) Excessive use of fertilisers over a long period may affect the alkalinity or acidity of the soil and may adversely affect the crop production. Thus, as a student of chemistry, we should suggest the farmer use only required quantities of nitrogen fertilisers.

Since the volume of the gaseous products is less than that of the gaseous reactants, high pressure should favour the oxidation of sulphur dioxide. But a very high pressure may cause the corrosion of the vessel in which oxidation is carried. Therefore, a pressure of 2 to 3 bar is sufficient for the oxidation.

(i) Liberation of hydrogen prevents the formation of FeCI₃. 
(ii) Structure of XeO₃