Question

Why pressure has no effect on the synthesis of HI?

Answer 1

(i) When the total number of moles of gaseous reactants and gaseous products are equal, the change in pressure has no effect on system at equilibrium. 

H₂(g) + I₂(g) ⇌ 2HI(g)

Here the number of moles of reactants and products are equal. So the pressure has no effect on such equilibrium with ∆n_g = O.