InterviewSolution
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InterviewSolution
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The emf of the cell : `H_(2)(g)|"Buffer||Normal"` canlomel elctrolde is `0.6885V` at `25^(@)C`, when barometric pressure is `=760 mm`. What is the pH of the buffer solution? `E_("calomel")=0.28V`A. `9.92`B. `7.92`C. `8.92`D. `6.92` |
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Answer» Correct Answer - D As the right electrode is normal (standard) electrode, the emf of cell may be written as `E_(cell)=E_("calomel")-E_(H^(+)("buffer")//H_(2))E_(cell)=E_("calomel")-E_(H^(+)("buffer")//H_(2))` or, `0.6885=0.28-E_(H^(+)//H_(2))` `thereforeE_(H^(+)//H_(2))=-0.4085V` Now, from Nernst equation, `E_(H^(+)//H_(2))=E_(H^(+)//H_(2))^(0)-(0.059)/(n)log.(P_(H_(2)))/([H^(+)]^(2))` `-0.4085=0-(0.059)/(2)` `or,(logP_(H_(2))-log[H^(+)]^(2))` or, `0.4085=(0.059)/(2)(log1+2P^(H))` `therefore`pH of buffer solution = `6.92` |
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