Partial Pressure of NO2 at equilibrium

Question

Consider the decomposition of N₂O₄(g) into NO₂(g).

N₂O₄ (g) ⇌ 2NO₂(g)      Kp = 47.9 at 400 K

Suppose that 1.00 atm of N₂O₄ decomposes and reaches equilibrium at 400 K. Determine the partial pressure of NO₂ at equilibrium.

Answer 1

Probably best to use an ICE table.

N₂O₄(g) <==> 2NO₂(g)

1.00...................0............Initial

-x.....................+2x..........Change

1.00-x................2x..........Equilibrium

Kp = (NO₂)² / (N₂O₄)

47.9 = (2x)² / 1-x

47.9 = 4x² / 1-x

4x² + 47.9x -47.9 = 0

x = 0.928 atm

Partial pressure NO₂ = 2x = 2 x 0.928 = 1.86 atm