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

PCl_{5}(g) ↔ PCl_{3}(g) + Cl_{2}(g)

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

We use **K _{p}** when dealing with pressure and

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

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

At a given temperature, the equilibrium constant (K_{p}) for the reaction PCl_{5}(g) ↔ PCl_{3}(g) + Cl_{2}(g) is 0.395 {also K_{p}= K_{c}(0.0821 T)}. What is the total pressure of the equilibrium system in mmHg if there are 100 mmHg of both PCl_{3}(g) and PCl_{5}(g) at equilibrium?

a. 400. mmHg

b. 300. mmHg

c. 595. mmHg

d. 500. mmHg

e. 200. mmHg

Frequently Asked Questions

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.