Question

consider the reaction below.
pcl₅(g)⇌pcl₃(g) + cl₂(g)
at 500 k, the reaction is at equilibrium with the following concentrations
pcl₅= 0.0095 m
pcl₃= 0.020
cl₂= 0.020 m
what is the equilibrium constant for the given reaction?
0.042
0.42
2.4
24

Explanation:

Step1: Write equilibrium - constant expression

For the reaction $\text{PCl}_5(g)
ightleftharpoons\text{PCl}_3(g)+\text{Cl}_2(g)$, the equilibrium - constant expression $K_c$ is $K_c=\frac{[\text{PCl}_3][\text{Cl}_2]}{[\text{PCl}_5]}$.

Step2: Substitute the given concentrations

We are given $[\text{PCl}_5]=0.0095\ M$, $[\text{PCl}_3]=0.020\ M$, and $[\text{Cl}_2]=0.020\ M$. Substitute these values into the $K_c$ expression: $K_c=\frac{0.020\times0.020}{0.0095}$.

Step3: Calculate the value of $K_c$

$K_c=\frac{0.020\times0.020}{0.0095}=\frac{0.0004}{0.0095}\approx0.042$.

Answer:

0.042