K_c is 1.67 × 10²⁰ at 25°C for the formation of iron(III) oxalate complex ion: Fe³⁺(aq) + 3 C₂O₄^2-(aq) ⇌ [Fe(C₂O₄) ₃]^3-(aq) .
If 0.0200 M Fe³⁺ is initially mixed with 1.00 M oxalate ion,what is the concentration of Fe³⁺ ion at equilibrium?

Question

Quizplus · Accepted Answer

Given the equilibrium constant (K) is 1.67 × 10^20 for the reaction, and the initial concentrations are 0.0200 M for Fe^3+ and 1.00 M for oxalate ion, we can set up an ICE table (Initial, Change, Equilibrium) for the reaction. Since K is very large, the reaction proceeds almost to completion, favoring the formation of the complex ion. However, the stoichiometry of the reaction shows that 1 mole of Fe^3+ reacts with 3 moles of oxalate ion, but given the large excess of oxalate, it's reasonable to assume that almost all of the Fe^3+ will be consumed. The small equilibrium concentration of Fe^3+ can be calculated using the quadratic formula or approximations based on the large value of K, leading to the answer 1.44 × 10^-22 M, which indicates that almost all Fe^3+ ions react to form the complex ion.

Kc Is 1

K_c Is 1