Equilibrium pressure of BrCl

Question

For the equilibriumBr2​+Cl2​<−−>2BrClthe equilibrium constant isKp=7.0at4000 K. If the cylinder is charged withBrClat an initial pressure of1.00 atmand the system allowed to come to equilibrium, what is the final (equilibrium) pressure ofBrCl

Answer 1

First we need to write the equation out. Next use an ice table and plug in the equilibrium values to Kp.

Br_2(g) + Cl_2(g) <--> 2BrCl_(g)

Initial 0 0 1.00

Change +x +x -2x

Equilibrium x x 1- 2x

Kp = [BrCl]²

[Br₂][Cl₂]

Kp = 7 = (1-2x)²

(x) ( x)

7x²= 1 + 4x² - 4x

7x² -1 - 4x² + 4x = 0

3x² + 4x - 1 = 0

Plug into quadratic formula to get x = 0.215

To find the concentration of BrCl [BrCl] = 1 - 2x = 1- 2(0.215) = 0.51 atm