Question

Consider the gas phase dissociation, PCl$_5$(g) $\rightleftharpoons$ PCl$_3$(g) + Cl$_2$(g) with equilibrium constant $K_p$ at a particular temperature and pressure $P$. The degree of dissociation ($\alpha$) for PCl$_5$(g) is

• A. $\alpha = \left(\frac{K_p}{K_p + P}\right)^{1/3}$
• B. $\alpha = \frac{K_p}{K_p + P}$
• C. $\alpha = \left(\frac{K_p}{K_p + P}\right)^{1/2}$
• D. $\alpha = \left(\frac{K_p}{K_p + P}\right)^2$

Hint:

Gas dissociation shortcut: \begin{itemize} \item Write ICE table \item Use total moles for partial pressure \item For small $\alpha$, simplify expressions \end{itemize}

Answer 1

The Correct Option is B