The exothermic reaction 2 HI(g) ⇌ + is at equilibrium at

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

Problem

The exothermic reaction 2 HI(g) ⇌ H2(g)H_2(g) + I2(g)I_2(g) ΔH∘<0\Delta H^\circ < 0 is at equilibrium at 700 K700\,\text{K}. The temperature is then increased to 750 K750\,\text{K} while the volume remains constant. Which statement best describes the immediate effect on QQ and KK, and the resulting direction of the net shift? (a) KK decreases while QQ remains unchanged; since Q<KQ < K, the system shifts toward HI. (b) KK decreases while QQ increases; since Q>KQ > K, the system shifts toward H2H_2 and I2I_2. (c) KK decreases while QQ remains unchanged; since Q>KQ > K, the system shifts toward HI. (d) KK increases while QQ remains unchanged; since Q>KQ > K, the system shifts toward HI.

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