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Electrochemistry

Question
CBSEENCH12011332
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Standard free energies of formation (in kJ/mol) at 298 K are -237.2, 394.4 and -8.2 for H2O (l), CO2 (g) and pentane (g),  respectively. The value of Ecello for pentane-oxygen fuel cell is

  • 1.968 V

  • 2.0968 V

  • 1.0968 V

  • 0.0968 V

Solution

C.

1.0968 V

Given,
increment straight G to the power of straight o subscript straight H subscript 2 straight O end subscript left parenthesis straight l right parenthesis space equals space minus space 237.2 increment straight G to the power of straight o subscript CO subscript 2 space space left parenthesis straight g right parenthesis space end subscript space equals space minus 394.4 increment straight G to the power of 0 subscript straight C subscript 5 straight H subscript 12 left parenthesis straight g right parenthesis space end subscript space equals space minus 8.2 straight C subscript 5 space straight H subscript 12 space plus space 16 space straight O subscript 2 space rightwards arrow space 5 CO subscript 2 space plus space 6 straight H subscript 2 straight O increment straight G to the power of straight o equals space 5 space straight x space increment straight G to the power of straight o subscript co subscript 2 end subscript space plus 6 space straight x space increment straight G to the power of 0 subscript straight H subscript 2 straight O end subscript space minus left parenthesis increment straight G to the power of straight o subscript straight C subscript 5 straight H subscript 12 space end subscript plus space increment straight G to the power of 0 subscript straight O subscript 2 end subscript right parenthesis equals space 5 space straight x space left parenthesis negative 394.4 right parenthesis space plus 6 space straight x space left parenthesis negative 237.2 right parenthesis space minus space left parenthesis negative 8.2 right parenthesis space plus 0 space equals space minus 3387 space kJ divided by mol In space pentane space minus oxygen space fuel space cell space 32 space space electrons space are space involved. increment straight G to the power of straight o space equals space nFE subscript cell to the power of straight o minus 3387 space straight x space 10 to the power of negative 3 end exponent space equals space 32 space straight x space 96500 space straight x space straight E subscript cell to the power of straight o straight E subscript cell to the power of straight o space equals space fraction numerator negative 3387 space straight x space 10 cubed over denominator 32 space straight x space 96500 end fraction space equals space fraction numerator negative 3387 over denominator 3088 end fraction space equals space 1.0968 space straight V

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