Question

${AB}_2\left(g\right)$ dissociates as $A{B}_2\left(g\right)\rightleftharpoons AB\left(g\right)+B\left(g\right)$. The initial pressure of ${AB}_2$ is $600mm$ $Hg$ and total pressure is $800mm$ $Hg$. The equilibrium constant for the reaction will be:

• A. $500mmHg$
• B. $100mmHg$
• C. $200mmHg$
• D. $400mmHg$

Answer 1

Answer: (B)

$100mmHg$

The given reaction is:-

${AB}_2\left(g\right)\rightleftharpoons AB\left(g\right)+B\left(g\right)$

Initial pressure : $600$ $0$ $0$

At eq. : $(600-p)$ $p$ $p$

Now, total pressure at equilibrium $=800mmHg$

$\Rightarrow 600-p+p+p=800$

$\Rightarrow p=200$

Now, $K_p=\frac{p_{AB}.p_B}{p_{{AB}_2}}=\frac{200\times 200}{400}=100mm$ mm Hg

Hence, option B is correct.