Question

At certain temperature (T) for the gas phase reaction
2H2O(g) + 2012 (g) = 4HĆI(g) + O2(g) K = 12 x 108 atm
If Cl, HCl & 0, are mixed in such a manner that the partial pressure of each is 2 atm and the mixture is brough
into contact with excess of liquid water. What would be approximate partial pressure of Cl, when equilibrium
is attained at temperature (T)?
[Given : Vapour pressure of water is 380 mm Hg at temperature (T)]
(A) 3.6 x 10-5 atm
(B) 10-4 atm
(C) 3.6 x10-3 atm (D) 0.01 atm​

Answer 1

(C) 3.6 x10-3 atm

Explanation:

Assume the vapor pressure of water as 2.99*10^−2atm.

2H2O + 2Cl2 ⇄ 4HCl + O2

0.0299    22-2x     22+4x   22+x

The equilibrium expression will be Kp = P(O2). P4(Hcl) / P2(H2o). P2(Cl2)

Kp = (2+x) (2+4x)^4 / (0.0299)^2.(2-2x)^2 = 12 * 10^8

Solving, we get:

x = 0.998

P(Cl2) = 2-2x = 3.6 * 10^-3

Option C is the answer.