Reaction X ⇌ Y is studied in two separate vessels at the same temperature

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

Problem

Reaction X ⇌ Y is studied in two separate vessels at the same temperature. Vessel 1 (sealed):

r_{f1} = 1.2 e^{-0.05 t}

r_{r1} = 0.40(1 - e^{-0.05 t})

Vessel 2 (open to the atmosphere so that some Y escapes):

r_{f2} = 1.2 e^{-0.05 t}

r_{r2} = 0.24(1 - e^{-0.05 t})

Rates are in

\text{mol}\,L^{-1}\,\text{s}^{-1}

and time

t

is in

\text{s}

. Which statement is most consistent with these rate expressions? (a) Both vessels reach dynamic equilibrium; Vessel 1 does so sooner because its reverse rate is larger. (b) Both vessels eventually reach equilibrium when both forward and reverse rates fall to zero. (c) Neither vessel reaches dynamic equilibrium because the forward rate continually decreases toward zero. (d) Only Vessel 1 can reach dynamic equilibrium; in Vessel 2 the escape of

Y

prevents the reverse rate from ever matching the forward rate.

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