A closed 2.0-L vessel at 298 K contains the gaseous equilibrium system 2 , NO _ 2 (g)…
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 2.0-L vessel at 298 K contains the gaseous equilibrium system
2NO2(g)⇌N2O4(g)
at a total pressure of 1.0 atm. The forward reaction is exothermic.
The system is at equilibrium when several separate stresses are applied, one at a time. No calculation of numerical values is required.
(a) A small pulse of pure NO2 is injected, instantly raising the partial pressure of NO2 while leaving temperature and volume unchanged. Describe the direction of the resulting net reaction and explain your reasoning.
(b) A portion of the gas mixture is withdrawn so that the partial pressure of N2O4 is instantly reduced, while temperature and volume remain constant. Describe the direction of the resulting net reaction and explain your reasoning.
(c) An inert gas is added at constant volume so that the total pressure doubles, but the partial pressures of NO2 and N2O4 remain unchanged. Predict whether any net reaction will occur and justify your answer.
(d) The temperature of the vessel is raised to 308 K while the volume remains unchanged. Predict the direction of the net reaction and justify your choice, taking into account the sign of ΔH.