# Problem: At a given temperature, the equilibrium constant (Kp) for the reaction PCl5(g) ↔ PCl3(g) + Cl2(g) is 0.395 {also Kp= Kc(0.0821 T)}. What is the total pressure of the equilibrium system in mmHg if there are 100 mmHg of both PCl3(g) and PCl5(g) at equilibrium?a. 400. mmHgb. 300. mmHgc. 595. mmHgd. 500. mmHge. 200. mmHg

###### FREE Expert Solution

We’re being asked to determine the total pressure at equilibrium.

PCl5(g) ↔ PCl3(g) + Cl2(g)

Recall that the equilibrium constant is the ratio of the products and reactants

We use Kp when dealing with pressure and Kc when dealing with concentration:

$\overline{){{\mathbf{K}}}_{{\mathbf{p}}}{\mathbf{=}}\frac{{\mathbf{P}}_{\mathbf{products}}}{{\mathbf{P}}_{\mathbf{reactants}}}}$     $\overline{){{\mathbf{K}}}_{{\mathbf{c}}}{\mathbf{=}}\frac{\mathbf{\left[}\mathbf{products}\mathbf{\right]}}{\mathbf{\left[}\mathbf{reactants}\mathbf{\right]}}}$

Note that solid and liquid compounds are ignored in the equilibrium expression.

###### Problem Details

At a given temperature, the equilibrium constant (Kp) for the reaction PCl5(g) ↔ PCl3(g) + Cl2(g) is 0.395 {also Kp= Kc(0.0821 T)}. What is the total pressure of the equilibrium system in mmHg if there are 100 mmHg of both PCl3(g) and PCl5(g) at equilibrium?

a. 400. mmHg

b. 300. mmHg

c. 595. mmHg

d. 500. mmHg

e. 200. mmHg

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Equilibrium Expressions concept. If you need more Equilibrium Expressions practice, you can also practice Equilibrium Expressions practice problems.