Question

For a reaction in a galvanic cell both ΔH° and ΔS° are positive. Which of the following statements is true?

Δ G° > 0 for all temperatures

ℰ°cell and ℰcell will be the same at all temperatures

ℰ°cell will increase with an increase in temperature

ℰ°cell will not change when the temperature increases

ℰ°cell will decrease with an increase in temperature

Answer 1

Option C is the correct statement.

ℰ°cell will increase with an increase in temperature

Step-by-step explanation:

To understand this problem it is neccessarry to state the relatioonships between the various paramenters mentioned in the question. these parameters include ΔH°, ΔS°, ΔG° and ℰ°Cell.

ΔH°, ΔS°, ΔG° are related with the following equation;

ΔG° = ΔH° - TΔS°

From the above equation we see that ΔG° cannot be greater than 0 for all temperatures. At higher temperatures, ΔG° becomes a negative value.

A spontaneous redox reaction is characterized by a negative value of ΔG and a positive value of ℰ°Cell, consistent with our earlier discussions. When both reactants and products are in their standard states, the relationship between ΔG° and ℰ°Cell is as follows:

ΔG∘=−nFℰ°Cell where;

F = Faraday and n = number of moles

Since ΔG° becomes negative at higher temperatures, it means ℰ°Cell would increase as temperature increases.

The relationship between G, Ecell and temperature can be given as;

Increase in Temperature = Negative value of G = Increase in E

Due to the fact established above; options B, D and E are false. This means the correct option is option C - ℰ°cell will increase with an increase in temperature