Question

Equilibrium constant, K_c for the reaction
\(N_2 (g) + 3H_2 (g) ⇋ 2NH_3 (g)\)
At 500 K is 0.061 At a particular time, the analysis shows that composition of the reaction mixture is 3.0 mol L^–1 N₂, 2.0 mol L^–1 H₂ and 0.5 mol L^–1 NH₃. Is the reaction at equilibrium? If not in which direction does the reaction tend to proceed to reach equilibrium?

Answer 1

Given:

Reaction:
N₂(g) + 3H₂(g) ⇋ 2NH₃(g)

Equilibrium constant at 500 K:
K_c = 0.061

Concentrations at a particular time:
[N₂] = 3.0 mol L⁻¹
[H₂] = 2.0 mol L⁻¹
[NH₃] = 0.5 mol L⁻¹

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Step 1: Write the expression for reaction quotient (Q_c)

For the reaction:

Q_c = [ NH₃ ]² / ( [ N₂ ] [ H₂ ]³ )

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Step 2: Substitute the given values

Q_c = (0.5)² / ( 3.0 × (2.0)³ )

Q_c = 0.25 / (3.0 × 8)

Q_c = 0.25 / 24

Q_c = 0.0104

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Step 3: Compare Q_c with K_c

Q_c = 0.0104
K_c = 0.061

Since Q_c < K_c, the reaction mixture is not at equilibrium.

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Step 4: Direction of reaction to reach equilibrium

When Q_c < K_c, the reaction proceeds in the forward direction.

This means more N₂ and H₂ will react to form NH₃ until equilibrium is attained.

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Final Answer:

The reaction is not at equilibrium.
Since Q_c < K_c, the reaction will proceed in the forward direction to reach equilibrium.