A closed vessel initially contains only gaseous substance X

CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)

Problem

A closed vessel initially contains only gaseous substance X, which can reversibly decompose to form gaseous substance Y according to the balanced equation X(g)⇌Y(g)X(g) \rightleftharpoons Y(g) At 25 ∘C25\,^{\circ}\text{C}, an experimenter measures the instantaneous rates of the two opposing processes just after the reaction mixture is prepared. The values are recorded below: • Rate of the process X→YX \rightarrow Y: 6.2×10−3 mol⋅L−1⋅s−16.2 \times 10^{-3}\,\text{mol}\cdot\text{L}^{-1}\cdot\text{s}^{-1} • Rate of the process Y→XY \rightarrow X: 2.5×10−3 mol⋅L−1⋅s−12.5 \times 10^{-3}\,\text{mol}\cdot\text{L}^{-1}\cdot\text{s}^{-1} Answer the following. (1) Part 1: (a) Identify the overall direction of net change in the composition of the system at this moment. (2) Part 2: (b) Explain your answer in part (a) by comparing the numerical values of the two measured rates.

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