A researcher studies the gas-phase equilibrium CO(g)+H_2O(g) CO_2(g)+H_2(g) H^ =-41
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A researcher studies the gas-phase equilibrium
CO(g)+H2O(g)⇌CO2(g)+H2(g)ΔH∘=−41kJmol−1
Starting with identical equilibrium mixtures at 600 K and 1.50 atm in 3.00 L containers, the researcher applies five unknown single stresses—labelled X, Y, Z, W, and Q—one to each container. After re-equilibration the partial pressures of CO2 in the five containers are determined and found to be:
X: 0.90 atm Y: 0.60 atm Z: 1.10 atm W: 0.45 atm Q: 0.75 atm
(1) Using only the CO2 data provided, rank the unknown stresses X, Y, Z, W, and Q from greatest to least in terms of how much they favor product formation.
(2) Propose a plausible chemical stress for each label (e.g., "decreased volume by half"), ensuring that your proposed set is consistent with the ranking you produced. Provide your reasoning for each proposal.
(3) Select one of your proposed stresses and derive an expression showing how the reaction quotient Qp immediately after that stress compares with the equilibrium constant Kp. Explain why the subsequent shift you predicted is required to restore equilibrium.