Compound C undergoes unimolecular rearrangement to two isomeric products, D and E
CHEMISTRY · Multi-part · A Level · Chemistry · Chemical equilibria (Le Chatelier’s principle and Kc) · Chemical equilibria (Le Chatelier’s principle and Kc)
Problem
Compound C undergoes unimolecular rearrangement to two isomeric products, D and E. At 400 K the standard Gibbs free energy change for the equilibrium
D ⇌ E
is ΔG° = –12.0 kJ mol⁻¹ (positive toward E). A chemist rapidly converts C to a mixture containing 90 % D and 10 % E (by mole) at 400 K and then allows the sealed system to stand isothermally for 3 h, long enough to reach equilibrium.
(a) Calculate the equilibrium constant K for the interconversion D ⇌ E at 400 K.
(b) Compute the reaction quotient Q for the initial 90 % D/10 % E mixture and state whether the composition will shift toward D or toward E as it approaches equilibrium.
(c) Determine ΔG for the initial mixture at 400 K.
(d) After equilibrium is reached, what will be the mole fraction of E in the final mixture? Show your reasoning.