Consider the reversible gas-phase reaction carried out in a closed cylinder at…

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 reversible gas-phase reaction 2NO2(g)⇌N2O4(g)2\text{NO}_2(g) \rightleftharpoons \text{N}_2\text{O}_4(g) carried out in a closed cylinder at constant temperature. Four students make the following claims about the reaction mixture after 3 minutes. Which student’s claim indicates that the reaction mixture has NOT yet reached equilibrium? (a) Only N2O4\text{N}_2\text{O}_4 is present, so the system is at equilibrium. (b) The forward rate is greater than the reverse rate, and the partial pressure of NO2\text{NO}_2 is still decreasing. (c) The forward rate equals the reverse rate, so the partial pressures are no longer changing. (d) The partial pressures of NO2\text{NO}_2 and N2O4\text{N}_2\text{O}_4 are equal, so the reaction has reached equilibrium.

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