For the reaction A(g) + 2B(g) 3C(g) , Kc = 27 at 300 K. If 0.5 moles of A and 2 moles of B are placed in a 1 L vessel, w

Practice question

Question

For the reaction A(g) + 2B(g) <=> 3C(g) , Kc = 27 at 300 K. If 0.5 moles of A and 2 moles of B are placed in a 1 L vessel, what is [C] at equilibrium?

Options

Choose one · Correct answer highlighted

0.9 M Correct 1.2 M 0.6 M 1.5 M

Explanation

Initial: [A] = 0.5 M , [B] = 2 M , [C] = 0 . Let 3x be moles of C formed, so A decreases by x , B by 2x . At equilibrium: [A] = 0.5 - x , [B] = 2 - 2x , [C] = 3x . Kc = ([C]³/[A][B]²) = ((3x)³/(0.5 - x)(2 - 2x)²) = 27 , (27x³/(0.5 - x)(4 - 4x + 4x²)) = 27 , x³ = (0.5 - x)(1 - x)² , x ≈ 0.3 , [C] = 3 × 0.3 = 0.9 M .

Share this question