Answer to Question #92434 in Chemistry for Tj

Question

The equilibrium constant for the reaction below is 0.18 at 25 oC.
PCl3(g) + Cl2(g)PCl5(g)

The following concentrations were measured from the reaction vessel: (4 marks)

[PCl3(g)] = 0.0420

[Cl2(g)] = 0.0240

[PCl5(g)] = 0.00500

Is this system in equilibrium? Explain.
If not, in which direction will the system shift?

Answer 1

To answer the question, we have to compare the trial product, Q , with K

If Q = K the system is at equilibrium

If Q < K , the reaction will shift to the right and produce more product.

If Q > K, the reaction will shift to the left.

Q is a trial product: [PCl₅]/[Cl₂][PCl₃] = 0.00500/0.0240(0.0420) = 4.96

Since 4.96 is greater than 0.18 the reaction proceeds to the left. By shifting left, the concentration of PCl₅ will decrease and Cl₂ and PCl₃ will grow.