Question

For the reaction N2(g) + 3 H2(g) equilibrium reaction arrow 2 NH3(g) at 25.0°C, the Kc of the reaction is 5.4 ✕ 105 and the ΔG° is −32.7 kJ/mol. Use the given concentrations to determine the following.

[N2] = 0.0027 M

[H2] = 0.0045 M

[NH3] = 0.20 M

(a) Determine the ΔG of the reaction.

(b) Determine which direction the reaction will proceed in order to reach equilibrium.

Answer 1

a)

N2 (g)   +    3 H2 (g)    <--------------> 2 NH3 (g)

0.0027        0.0045                              0.20 M

Qc = [NH3]^2 / [N2][H2]^3

     = (0.20)^2 / (0.0027)(0.0045)^3

Qc = 1.6 x 10^8

ΔG = ΔG° + RT ln Qc

     = - 32.7 + 8.314 x 10^-3 x 298 x ln (1.6 x 10^8 )

ΔG = 14.1 kJ/mol

b)

here Qc = 1.6 x 10^8

Kc = 5.4 x 10^5

Qc > Kc. so the reaction will proceed to left direction or reverse direction to reach equilibrium