Which of the following reactions will get affected by increasing the pressure? Also mention whether chasnge will cause the reaction to go into forward or backward direction.
(i) `COCl_(2)(g)hArrCO(g)+Cl_(2)(g)`
(ii) `CH_(4)(g)+2S_(2)(g)hArrCS_(2)(g)+2H_(2)S(g)`
(iii) `CO_(2)(g)+C(s)hArr2CO(g)`
(iv) `4NH_(3)+(g)+5O_(2)(g)hArr4NO(g)+6H_(2)O(g)`

Explanation

A. According to Le Chatelier's principle when pressure is increased on equilibrium, the equilibrium shift in the direction where the number of gaseous molecules are less.
(i) `COCl_(2)(g)hArrCO(g)+Cl_(2)(g)`
In this reaction the number of gaseous reactant molecules (1) are less than the total number of gaseous molecules (2) of products. So increase pressure shifts the equilibrium in backward direction.
(ii) `CH_(4)(g)+2S_(g)hArrCS_(2)(g)+2H_(2)S(g)`
In this reaction the total number of gaseous reactant molecules (3) are equal to the total number of gaseous product molecules (3). So pressure has no effect on this equilibrium.
(iii) `CO_(2)(g)+C(s)hArr2CO(g)`
In this reaction the number of gaseous reactant molecules (1) is less than the total number of gaseous product molecules (2). So increase in pressure shifts the equilibrium in the backward direction.
(iv) `4NH_(3)(g)+5O_(2)(g)harr4NO(g)+6H_(2)O(g)`
In this reaction the sum of the number of gaseous reactant molecules (g) is less than the sum of the number of the gaseous product molecules (10). So the increase in pressure shifts the equilibrium in the backward direction.