Question

A definite amount of solid ${NH}_{4}HS$ is placed in a flask already containing ammonia gas at a certain temperature and $0.50$ atm pressure. ${NH}_{4}HS$ decomposes to give ${NH}_3$ and $H_{2}S$ and at equilibrium total pressure in flask is $0.84$ atm. The equilibrium constant for the reaction is:

• A. $0.30$
• B. $0.18$
• C. $0.17$
• D. $0.11$

Answer 1

Answer: (D)

$0.11$

$N{H}_{4}HS\left(s\right)\rightleftharpoons N{H}_3\left(g\right)+H_{2}S\left(g\right)$

Initial $a$ $0.5atm$ $0atm$

equilibrium $a-x$ $0.5+x$ $x$

Total pressure $=0.5+x+x$

$=0.5+2x$

i.e. $x=0.17$

$K_p=P_{N{H}_3}\cdot P_{H_{2}S}$

$=\left(0.67\right)\times \left(0.17\right)$

$K_p=0.1139$

So, option $D$ is correct.