Question

Balance the following redox equation, identifying the element oxidized and the element reduced. Show all work to solve the problem.

Cr2O7 2- + C2H5OH --> Cr3 + CO2

Answer 1

Step-by-step explanation:

A redox equation is defined as an equation that shows reduction and oxidation are taking place simultaneously in a chemical reaction.

When electrons are lost in a chemical reaction then it is known as oxidation reaction. Whereas when electrons are gained in a chemical reaction then it is known as a redox reaction.

For example,
`Cr_(2)O^(2-)_(7) + C_(2)H_(5)OH \rightarrow Cr^(3+) + CO_(2)`

Reduction-half reaction:
`Cr_(2)O^(2-)_(7) + 3e^(-1) \rightarrow Cr^(3+)`

Oxidation state of Cr in
`Cr_(2)O^(2-)_(7)` is +6.

Oxidation-half reaction:
`C_(2)H_(5)OH \rightarrow CO_(2) + 6e^(-1)`

Oxidation state of C in
`C_(2)H_(5)OH` is -2 and in
`CO_(2)` oxidation state of C is +4.

Now, to balance the equation multiply reduction-half reaction by 2.

`2Cr_(2)O^(2-)_(7) + 6e^(-1) \rightarrow 2Cr^(3+)`

Thus, the combined balanced chemical reaction equation will be as follows.

`2Cr_(2)O^(2-)_(7) + C_(2)H_(5)OH \rightarrow 2Cr^(3+) + CO_(2)`

Answer 2

Oxygen, a chalcogen, has oxidation state 2-. Therefore, Cr is Cr2O7^2- has a charge of 6+. This charge becomes 0 after the reaction, so Cr gained electrons and was reduced. This also means that Cr2O7 was the oxidizing agent.

Meanwhile, since H has a charge of 1+, the oxidation state of C in C2H5OH is 2-. In the product CO2, its charge is 4+. This means that it lost electrons, and was oxidized. Therefore, ethanol (C2H5OH) is the reducing agent.