Question

The overall reaction 2Co3+(aq) + 2Cl-(aq) ? 2Co2+(aq) + Cl2(g) has the standard cell voltage Eocell= 0.46 V.

Given that Cl2(g) + 2e-? 2Cl-(aq), Eo = 1.36 V,

calculate the standard reduction potential for the following the half reaction at 25oC:

Co3+ + e-? Co2+

1.82 V
-0.90 V
0.90 V
-1.82 V

Answer 1

Answer: Option (a) is the correct answer.

Step-by-step explanation:

The given overall reaction will be as follows.

`2Co^(3+)(aq) + 2Cl^(-)(aq) \rightarrow 2Co^(2+)(aq) + Cl_(2)(g)`

It is given that standard potential of the cell is 0.46 V.

Hence, the oxidation and reduction half reactions of the cell are as follows.

Reduction-half reaction:
`Cl_(2)(g) + 2e^(-) \rightarrow 2Cl^(-)(aq)`,
`E^(o) = 1.36 V`

Oxidation-half reaction:
`2Co^(3+)(aq) \rightarrow 2Co^(2+)(aq)`,
`E^(o) = ?`

Now, expression of
`E^(o)_(cell)` of this reaction is as follows.

`E^(o)_(cell) = E^(o)_(Co^(3+)/Co^(2+)) - E^(o)_{Cl_(2)/Cl^(-)}`

Putting the given values into the above formula as follows.

0.46 V =
`E^(o)_(Co^(3+)/Co^(2+))` - 1.36 V

`E^(o)_(Co^(3+)/Co^(2+))` = 1.82 V

Thus, we can conclude that standard potential of the given half cell is 1.82 V.