Question

Ammonium hydrogen sulphide is contained in a closed vessel at $313K$ when total pressure at equilibrium is found to be $0.8$ atm. The value of $K_p$ for the reaction,
${NH}_{4}HS\left(s\right)\rightleftharpoons {NH}_3\left(g\right)+H_{2}S\left(g\right)$ is:

• A. $0.16$
• B. $1.6$
• C. $0.016$
• D. $16$

Answer 1

The correct option is A $0.16$

Ammonium hydrogen sulphide is contained in a closed vessel at $313K$ when total pressure at equilibrium is found to be $0.8$ atm.
${NH}_{4}HS\left(s\right)\rightleftharpoons {NH}_3\left(g\right)+H_{2}S\left(g\right)$
$P_{N{H}_3}=P_{H_{2}S}=P$

Total pressure $P_{N{H}_3}+P_{H_{2}S}=P+P=2P$

But total pressure is 0.8 atm.

$2P=0.8$

$P=0.4$ atm

$P_{N{H}_3}=P_{H_{2}S}=P=0.4$ atm
The value of the equilibrium constant for the reaction, is $K_p=P_{N{H}_3}\times P_{H_{2}S}$

$K_p=0.4\times 0.4$

$K_p=0.16$