Question

$PC{l}_5$ dissociates according to the reaction $PC{l}_5\left(g\right)\rightleftharpoons PC{l}_3\left(g\right)+C{l}_2\left(g\right)$. At 523 K, $K_p=1.78atm$. Find the density of the equilibrium mixture at a total pressure of 1 atm :

• A. 0.271 g/L
• B. 2.71 g/L
• C. 27.1 g/L
• D. None of these

Answer 1

The correct option is B 2.71 g/L

$\underset{P_0(1-\alpha )}{PC{l}_5}\rightleftharpoons \underset{P_0\alpha }{PC{l}_3}+\underset{P_0\alpha }{C{l}_2}$

$1.78=\frac{P_0{\alpha }^2}{1-\alpha }$

$P_0(1+\alpha )=1$

$M_{avg}=\frac{208.5}{1+\alpha }$

$d_{mix}=\frac{[1\times \frac{208.5}{1+\alpha }]}{0.0821\times 523}=2.71g/L$