Question

Using half-reactions, balance the equation for the redox reaction when Cr2O2 -7 (aq) andFe2+(aq) react to form Cr3+(aq) andFe3+(aq) in acidic solution.

Answer 1

Answer : Cr2O72-(aq) + 6 Fe2+(aq) + 14 H+ → 2 Cr3+(aq) + 6 Fe3+(aq) + 7 H2O

• The equation of the redox half-reactions is given as follows:

Cr2O2^-7(aq) + Fe^2+ (aq) → Cr^3+(aq) + Fe^3+(aq)

• adding this to n acidic solution will produce the following: see equations in the box below:

`\begin{gathered} 1.Balance\text{ the Cr atom } \\ \rightarrow Cr_2O^(2-)_7+6e^-\rightarrow2cr^(3+) \\ 2.\text{ Balance the }Fe\text{ electrons by multiplying with 6 } \\ \rightarrow6Fe^(2+)\rightarrow6Fe^{3+\text{ }} \\ 3.\text{ Balance the oxygen atoms },\text{ 7Oxygen on the left side, so 7Oxygen on the right side } \\ \rightarrow Cr_2O^{2-\text{ }}_{7^{}}+6Fe^(2+)+\text{ }\rightarrow6Fe^{3+\text{ }}+2Cr^(3+)+\text{ }7H2O \\ 4\text{. balance the H atoms } \\ \rightarrow Cr_2O^{2-\text{ }}_7+6Fe^(2+)+\text{ }14H^+\rightarrow6Fe^(3+)+2cr^(3+)+7H_2O \end{gathered}`

Answer : Cr2O72-(aq) + 6 Fe2+(aq) + 14 H+ → 2 Cr3+(aq) + 6 Fe3+(aq) + 7 H2O