Consider the gaseous equilibrium at constant temperature: A(g) + 2 B(g) ⇌ 3 C(g)…

CHEMISTRY · Single correct · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)

Problem

Consider the gaseous equilibrium at constant temperature: A(g) + 2 B(g) ⇌ 3 C(g) Initially at equilibrium the partial pressures are

P_A = 0.40\,\text{atm}

P_B = 0.60\,\text{atm}

, and

P_C = 0.20\,\text{atm}

. Some B is rapidly withdrawn, lowering

P_B

0.30\,\text{atm}

while

P_A

and

P_C

are momentarily unchanged. Which statement is most consistent with the state of the system immediately after the withdrawal? (a)

Q < K

and the forward reaction rate exceeds the reverse, so the system shifts to the right. (b)

Q > K

and the reverse reaction rate exceeds the forward, so the system shifts to the left. (c)

Q > K

but the system will shift to the right to replenish the removed

\mathrm{B}

. (d)

Q = K

so the system remains at equilibrium with no net shift.

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