Question

$5 \cdot 1 \,g NH _{4} SH$ is introduced in $3.0 \,L$ evacuated flask at $327^{\circ} C .30 \%$ of the solid $NH _{4} SH$ decomposed to $NH _{3}$ and $H _{2} S$ as gases. The $Kp$ of the reaction at $327{ }^{\circ} C$ is
$\left( R =0 \cdot 082 L\right.$ atm $mol ^{-1} \,K ^{-1}$, Molar mass of $S =32 \,g \,mol /{ }^{01}$, molar mass of $N =14 \,g \,mol ^{-1}$ )

• A. $1 \times 10^{-4} \, atm^2$
• B. $4.9 \times 10^{-3} \, atm^2$
• C. $0.242 \, atm^2$
• D. $0.242 \times 10^{-4} \, atm^2$

Answer 1

Answer: (C)

Now use $PV = nRT$ at equilibrium
$P_{\text {total }} \times 3$ lit $=(.03+.03) \times .082 \times 600$
$P_{\text {total }}=.984 \,atm$
At equilibrium
$P_{N H_{3}}=P_{H_{2} S}=\frac{P_{\text {total }}}{2}=.492$
$k_{P}=P_{N H_{3}} \cdot P_{H_{2} S}=(.492)(.492)$
$k_{p}=.242\, atm ^{2}$