Question

In analytical chemistry, solutions of potassium dichromate, K2Cr2O7 (a powerful oxidizing agent), are used to determine the amount of iron present in samples. This analysis is carried out by reacting iron(II) with an acidic solution containing Cr2O72−. During the reaction, the orange dichromate ion forms green Cr3+ ion, and iron(II) ion is oxidized to iron(III) ion. What is the overall ionic equation for this reaction? Including the phases is optional. Express your answer as a chemical equation.

A) 2Fe^2+ + Cr2O7^2- → 2Fe^3+ + 2Cr^3+
B) K2Cr2O7 + 3Fe^2+ + 14H^+ → 2Cr^3+ + 3Fe^3+ + 2K^+ + 7H2O
C) Fe^2+ + K2Cr2O7 + H+ → Fe^3+ + Cr^3+ + K+ + H2O
D) 2K^+ + 2Cr2O7^2- + 6Fe^2+ → 2Cr^3+ + 6Fe^3+ + 2K+

Answer 1

The overall balanced ionic equation for the reaction between iron(II) and potassium dichromate in an acidic solution is 6Fe2+ (aq) + Cr2O72- (aq) + 14H+ (aq) → 6Fe3+ (aq) + 2Cr3+ (aq) + 7H2O (l).

Step-by-step explanation:

The correct overall ionic equation for the reaction between iron(II) and potassium dichromate in acidic solution, forming iron(III) and chromium(III) ions is:
6Fe2+ (aq) + Cr2O72- (aq) + 14H+ (aq) → 6Fe3+ (aq) + 2Cr3+ (aq) + 7H2O (l)

This reaction demonstrates the concept of conservation of electrons, where the oxidation of iron(II) to iron(III) releases electrons that are then used to reduce chromium(VI) in the dichromate ion to chromium(III).