A gaseous mixture contains 0.30 moles CO, 0.10 moles H₂, and 0.03 moles H₂O vapour and an unknown amount of CH₄ per litre. This mixture is at equilibrium at 1200 K.
CO(g) + 3H₂(g) ⇌ CH₄(g) + H₂O(g)

Question

A gaseous mixture contains 0.30 moles CO, 0.10 moles H₂, and 0.03 moles H₂O vapour and an unknown amount of CH₄ per litre. This mixture is at equilibrium at 1200 K.
CO(g) + 3H₂(g) ⇌ CH₄(g) + H₂O(g); K_c = 3.9
What is the concentration of CH₄ in this mixture? The equilibrium constant K_c equals 3.92.

Prashant Kotian · Accepted Answer

Correct answer: B. The given concentrations per litre are [CO] = 0.30 M, [H₂] = 0.10 M, and [H₂O] = 0.03 M. Using K_c = ([CH₄][H₂O]) / ([CO][H₂]³), we get 3.9 = ([CH₄] × 0.03) / (0.30 × 0.10³). 3.9 = ([CH₄] × 0.03) / 0.0003. [CH₄] = (3.9 × 0.0003) / 0.03 = 0.039 M. Therefore, correct answer is B.

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