Question

$X{Y}_2$ dissociates $X{Y}_2\left(g\right)\rightleftharpoons XY\left(g\right)+Y\left(g\right)$. When the initial pressure of $X{Y}_2$ is $600$ mm Hg, the total equilibrium pressure is $800$ mm Hg. Calculate $K$ for the reaction. Assuming that the volume of the system remains unchanged :

• A. $50.0$
• B. $100.0$
• C. $166.6$
• D. $400.0$

Answer 1

The correct option is B $100.0$

$\underset{\underset{P-x}{P}}{X{Y}_2}\rightleftharpoons \underset{\underset{x}{0}}{XY}+\underset{\underset{x}{0}}{Y}$
Initial $P=600$ mm Hg, Final $P=800mmHg$
Total moles $\propto$ final P.
$\therefore P-x+x+x\propto 800$
$600-x+x+x\propto 800$
$x=200mmHg$
$K=\frac{x\times x}{P-x}=\frac{200\times 200}{400}=100Hg$