Question

If you place 65.5 g of NOCl in a 2.0 L reaction flask at 500 K, and once the equilibrium below has been established the total pressure is 21.6 atm, what is Kp for the reaction?

2 NOCl (g) <--> 2 NO (g) + Cl2 (g)

Answer 1

moles of NOCl = 65.5 / 65.46 = 1.0 mol

volume = 2 l

temperature = 500 K

P V = n R T

P x 2 = 1 x 0.0821 x 500

P = 20.525 atm

2 NOCl (g) <---------> 2 NO (g) + Cl2 (g)

20.525                         0              0

20.525 - 2x                  2x             x

total pressure at equilibrium :

20.525 - 2x + 2x+ x = 21.6

x = 1.075

PNOCl = 20.525 - 2 x 1.075 = 18.375

PNO = 2.15

PCl2 = 1.075

Kp = P²NO x PCl2 / P²NOCl

      = 2.15^2 x 1.075 / 18.375^2

     = 0.0147

Kp = 0.0147

     =