A chemist is investigating an unknown reversible reaction that involves species A, B
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
A chemist is investigating an unknown reversible reaction that involves species A, B, and C. The only information available is the following set of concentration changes observed from the start of the experiment until the system reaches equilibrium.
• Initial concentrations (t = 0 min): [A] = 0.600 M, [B] = 0 M, [C] = 0 M.
• At equilibrium: [A] decreases by 0.300 M, [B] increases by 0.400 M, and [C] increases by 0.200 M.
Assume no other species are present and that the temperature is constant.
Using only these data, address the tasks below.
(a) Propose the simplest balanced chemical equation consistent with the observed concentration changes. Clearly identify the role of each species as reactant or product.
(b) Explain how the relative magnitude of the concentration changes leads to the stoichiometric coefficients in your proposed equation.
(c) Suppose a second trial is performed with the same initial concentration of A but with an additional 0.100 M of C introduced at t = 0 min. Predict qualitatively whether the equilibrium concentration of A will be greater than, equal to, or less than 0.300 M below its initial value. Provide a chemical justification for your prediction.
(d) Design a concise experimental procedure (no more than three essential steps) that would allow another student to verify whether your proposed balanced equation is correct using concentration–versus–time measurements.