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

We can set up an ICE table for this reaction at 250ºC:

|          | PCl5        | Cl2         | PCl3        |
|----------|-------------|-------------|-------------|
| Initial  | 2.74 atm    | 0 atm       | 0 atm       |
| Change   | -x          | -x          | +x          |
| Equilibrium | 2.74 - x  |  - x        | x           |

Substituting these values into the equilibrium expression, we get:

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

Solving for x using the quadratic formula gives us:

x = 1.24 atm

Therefore, the pressure of PCl5 at equilibrium is:

2.74 - x = 1.50 atm

The correct choice is B, with a pressure of 1.50 atm.

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

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