Question

$X{Y}_2$ dissociates as: $X{Y}_2\left(g\right)\rightleftharpoons XY\left(g\right)+Y\left(g\right)$
Initial pressure of $X{Y}_2$ is $600mm$ $Hg$. The total pressure at equilibrium is $800mm$ $Hg$. Assuming volume of system to remain constant, the value of $K_p$ is:

• A. $50$
• B. $100$
• C. $200$
• D. $400$

Answer 1

Answer: (B)

$X{Y}_2$ dissociates as:

$X{Y}_2\left(g\right)\rightleftharpoons XY\left(g\right)+Y\left(g\right)$

Initial pressure of $X{Y}_2$ is $600mm$ $Hg$. The total pressure at equilibrium is $800mm$ $Hg$.

Let $xmm$ $Hg$ of $X{Y}_2$ dissociates to reach equilibrium. $xmm$ $Hg$ of $XY$ and $xmm$ $Hg$ of $Y$ will be formed at equilibrium. $600-xmm$ $Hg$ of $X{Y}_2$ will be present at equilibrium.

Total pressure $=(600-x)+x+x=600+xmm$ $Hg$

But total pressure $=800mm$ $Hg$

$600+x=800$ or $x=200$