CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
Water–gas shift reaction:
CO(g)+H2O(g)⇌CO2(g)+H2(g)
A student places 0.400 mol of each of the four reactive species into a 5.00 L rigid vessel at 1000 K and allows the system to reach equilibrium.
Analysis of the equilibrium mixture shows that 0.170 mol of CO2 is present in the vessel.
(1) Determine the equilibrium molar concentration of every species present in the container.
(2) Calculate the equilibrium constant Kc for the reaction at 1000 K.
(3) With the volume held constant, 1.00 mol of helium gas is injected into the vessel at the same temperature. The system is allowed to re-establish equilibrium. Predict the direction in which the reaction will shift, and justify your answer without performing a numerical calculation.
(4) Calculate the new partial pressure of each reactive species after the system has come to its new equilibrium. Assume ideal-gas behavior and include a brief statement explaining why the value of Kc does or does not change.