A sealed, rigid container at contains the brown–colored equilibrium mixture…
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A sealed, rigid container at 298K contains the brown–colored equilibrium mixture represented by the equation below.
N2O4(g)⇌2NO2(g)
After the system has reached equilibrium, a student quickly injects a small quantity of pure NO2(g) into the vessel. No other changes are made to the temperature, volume, or pressure of the system.
(a) Describe qualitatively how the rate of the forward reaction compares with the rate of the reverse reaction in the instant immediately following the NO2 injection.
(b) Predict the direction in which the equilibrium will shift as the system re-establishes equilibrium. Justify your answer in terms of a change to the reaction quotient Qc relative to the equilibrium constant Kc.
(c) Once the new equilibrium is attained, state whether the equilibrium concentrations of each of the following species are greater than, less than, or equal to their original equilibrium values. Provide a brief justification for each.
(i) [NO2] (ii) [N2O4]
(d) Explain why the numeric value of Kc for the reaction remains unchanged even though the color of the mixture is observed to fade after equilibrium is re-established.