At 250ºC, the equilibrium constant K_p for the reaction PCl₅(g) PCl₃(g)+ Cl₂(g)is 1.80.Sufficient PCl₅ is put into a reaction vessel to give an initial pressure of 2.74 atm at 250ºC.Calculate the pressure of PCl₅ after the system has reached equilibrium.

Question

Quizplus · Accepted Answer

The balanced chemical equation for the given reaction is:

PCl5(g) ⇌ PCl3(g) + Cl2(g)

The equilibrium constant (K) at 250ºC is given as 1.80.

Initial pressure of PCl5(g) = 2.74 atm

Let the change in pressure be -x atm.

At equilibrium, the pressure of PCl5 is (2.74 - x) atm, the pressure of PCl3 is x atm, and the pressure of Cl2 is x atm.

Substituting the equilibrium pressures into the equilibrium expression for K:

K = [PCl3] [Cl2] / [PCl5]
1.80 = x^2 / (2.74 - x)

Solving for x, we get:

x = 1.24 atm

Therefore, the pressure of PCl5 at equilibrium is:

2.74 - x = 2.74 - 1.24 = 1.50 atm

Hence, the correct answer is B) 1.24 atm.

At 250ºC, the Equilibrium Constant Kp for the Reaction PCl5(g)

At 250ºC, the Equilibrium Constant K_p for the Reaction PCl₅(g)