i. H2(g) + I2(g) ⇌ 2HI(g), KC = 20 at 550 K ii. H2(g) + Cl2(g) ⇌ 2HCl(g), KC= 10^(18) at 550 K

Question

Comment on the extent to which the forward reaction will proceed, from the magnitude of the equilibrium constant for the following reactions :

i. H_2(g) + I_2(g) ⇌ 2HI_(g), K_C = 20 at 550 K

ii. H_2(g) + Cl_2(g) ⇌ 2HCl_(g), K_C= 10¹⁸ at 550 K

Answer 1

i. H_2(g) + I_2(g) ⇌ 2HI_(g), K_C = 20 at 550 K

For the reaction, 

K_C = 20 at 550 K 

If the value of K_C is the range of 10^-3 to 10³,

The forward and reverse proceed to equal extents.

Hence,

The given reaction will form appreciable concentrations of both reactants and the product at equilibrium.

ii. H_2(g) + Cl_2(g) ⇌ 2HCl_(g), K_C= 10¹⁸ at 550 K

For the reaction,

K_C= 10¹⁸ at 550 K

If the value of K_C >>> 10³, forward reaction is favoured.

Hence,

The given reaction will proceed in the forward direction and will nearly go to completion.