Suppose that a hydrogen fuel cell, as described in the text, is to be operated at 75° C and atmospheric pressure. We wish to estimate the maximum electrical work done by the cell using, only the room-temperature data at the back of this book. It is convenient to first establish a zero-point for each of the three substances, H2 O2, and H20. Let us take G for both H2 and O2 to be zero at 25°C, so that G for a mole of H20 is -237 kJ at 25°C.(a) Using these conventions, estimate the Gibbs free energy of a mole of H2 at 75°C. Repeat for O2 and H20.(b) Using the results of part (a), calculate the maximum electrical work done by the cell at 75°C, for one mole of hydrogen fuel. Compare to the ideal performance of the cell at 25°C.
Suppose that a hydrogen fuel cell, as described in the text, is to be operated at 75° C and atmospheric pressure. We wish to estimate the maximum electrical work done by the cell using, only the room-temperature data at the back of this book. It is convenient to first establish a zero-point for each of the three substances, H2 O2, and H20. Let us take G for both H2 and O2 to be zero at 25°C, so that G for a mole of H20 is -237 kJ at 25°C.
(a) Using these conventions, estimate the Gibbs free energy of a mole of H2 at 75°C. Repeat for O2 and H20.
(b) Using the results of part (a), calculate the maximum electrical work done by the cell at 75°C, for one mole of hydrogen fuel. Compare to the ideal performance of the cell at 25°C.
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