Consider the generic equilibrium A_2(g) + B_2(g) ; ;2 ,AB(g) A student plans to…
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
Consider the generic equilibrium
A2(g)+B2(g)⇌2AB(g)
A student plans to determine the equilibrium constant experimentally by introducing known amounts of A2 and B2 into a sealed vessel, allowing the system to reach equilibrium, and then measuring the amount of AB present. Helium gas may later be added to test whether the equilibrium constant changes.
(1) Describe, in a logically ordered sequence, the steps the student should follow to convert the measured number of moles of each species and the vessel volume into equilibrium molar concentrations.
(2) Explain how the stoichiometric relationship among the species can be used to relate the change in concentration of one species to the changes in the others when calculating the equilibrium constant.
(3) Discuss why adding helium gas at constant volume and temperature does not alter the numerical value of the equilibrium constant, even though partial pressures of the reacting gases change.