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Electrochemistry

Question
CBSEENCH12011054

The pressure of H2 required to make the potential of H2-electrode zero in pure water at 298 K is

  • 10-12 atm

  • 10-10 atm

  • 10-4 atm

  • 10-14 atm

Solution

D.

10-14 atm

From the question, we have an equation
2H+ +2e- --> H2(g)
According to Nernst equation
straight E space equals space straight E to the power of 0 space minus fraction numerator 0.0591 over denominator 2 end fraction log space fraction numerator straight p subscript straight H subscript 2 end subscript over denominator left square bracket straight H to the power of plus right square bracket squared end fraction
0 minus fraction numerator 0.0591 over denominator 2 end fraction space log space fraction numerator straight p subscript straight H subscript 2 end subscript over denominator left parenthesis 10 to the power of negative 7 end exponent right parenthesis squared end fraction
left square bracket therefore space left square bracket straight H to the power of plus right square bracket space equals 10 to the power of negative 7 end exponent right square bracket

therefore space For space potential space of space straight H subscript 2 space electrode space to space zero space comma space pH subscript 2 space should space be space equal space to space left square bracket straight H to the power of plus right square bracket squared comma space straight i. straight e space 10 to the power of negative 14 end exponent space atm
log space fraction numerator 10 to the power of negative 14 end exponent over denominator left parenthesis 10 to the power of negative 7 end exponent right parenthesis squared end fraction space equals 0