Find the concentration of NO and Cl2 .

Question

At 473 K,

for the elementary reaction 2NOCl(g)k1⇌k−12NO(g)+Cl2(g)

k1=7.8×10−2L/mols and k−1=4.7×102L2/mol2s

A sample of NOCl is placed in a container and heated to 473 K. When the system comes to equilibrium, [NOCl] is found to be 0.12 mol/L .

Answer 1

2NOCl(g) <--k₁/k_-1--> 2NO(g) + Cl₂(g)

0.12 M...........................2x...........x.........equilibrium concentrations

Find Keq:

Keq = k₁ / k_-1 = 7.8x10^-2 / 4.7x10²

Keq = 1.66x10^-4

Writing the Keq expression and solving for x:

Keq = [NO]²[Cl₂] / [NOCl]² = (2x)²(x) / (0.12)²

1.66x10^-4 = 4x³ / 0.0144

x³ = 5.98x10^-7

x = 8.42x10-3 M

[NO] = 2x = 1.68x10^-2 M = 0.0168 M

[Cl₂] = 8.42x10^-3 M = 0.00842 M