Suppose you have a hydrogen-oxygen fuel cell with the overall reaction: The corr

Question

Suppose you have a hydrogen-oxygen fuel cell with the overall reaction:

The corresponding Nernst equation is given above, in which PH2O is the gas pressure of water vapor, PH2 the hydrogen gas pressure, and PO2 that of oxygen. Given the above, which of the follow statement(s) are TRUE. No knowledge of fuel cells is required – just a fundamental ability to read and interpret a mathematical expression.

0RT 2 H2 0 Suppose you have a hydrogen-oxygen fuel cell with the overall reaction: H2 (g) + ½ O2 (g)-> H2O (g) ->H20 The corresponding Nernst equation is given above, in which PH20 is the gas pressure of water vapor, PH2 the hydrogen gas pressure, and Po2 that of oxygen. Given the above, which of the follow statement(s) are TRUE. No knowledge of fuel cells is required -just a fundamental ability to read and interpret a mathematical expression (To receive credit you must select all the TRUE statements and NOT select those that are false.) Temperature Thas no effect on the cell potential Ecell If the pressure of oxygen gas Pos is increased the cell potential Ec will cell increase. As the fuel cell runs and water vapor PH2o accumulates, the cell potential Ecell should decrease. o Tripling the hydrogen pressure PH2 will reduce the cell potential Ecell by 1/3

Explanation / Answer

The equation is

Ecell = E0cell - (RT/2F)xln(PH2O / PH2x P1/2O2)

1. The given equation is a function of T and hence Ecell depends on temperature. Hence 1st option is False and not our answer.

2. As we increase the value of PO2, the value of P1/2O2 will also increase and hence the value of (RT/2F)xln(PH2O / PH2x P1/2O2) decrease. This results an increase in the value of Ecell. Hence 2nd option is correct and one of our answers.

3: As water vapor accumulates, the value of PH2O will increase. This causes an increase in the value (RT/2F)xln(PH2O / PH2x P1/2O2). Hence the value of Ecell decreases. Hence 3rd option is also correct and one of our answers.

4: Ecell is a logarithm function of PH2. and not a linear function. Hence tripling PH2 will not reduce the Ecell by 1/3. Hence this statement is false and not our answer.

Hence only 2nd and 3rd options are true and we need to click on 2nd and 3rd option

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