Question

A small amount of $N{H}_{4}HS$ is placed in a flask already containing ammonia gas at a certain temperature and $0.50$ atm pressure. Ammonium hydrogen sulphide decomposes to yield $N{H}_3$ and $H_{2}S$ gases in the flask. When the decomposition reaction reaches equilibrium, the total pressure in the flask rises to $0.84$ atm. The equilibrium constant for $N{H}_{4}HS$ decomposition at this temperature is :

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

Answer 1

The correct option is D $0.11$

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

At initial stage pressure are

$0$ atm. $0.5$atm. $0$ atm

At equilibrium stage

$0$ atm. $0.5$+ $x$ $x$

Total pressure at equilibrium= $0.5$+$2x$=$0.84$

$x$= $0.17$atm

$k_p$= $P_{N{H}_3}\times P_{H_{2}S}$

= ($0.5$+$0.17$)$\times 0.17$

= $0.11at{m}^2$