InterviewSolution
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InterviewSolution
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The pH of a `10^(-8)` molar solution of HCl in water isA. 8B. `-8`C. Between 7 and 8D. Between 6 and 7 |
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Answer» Correct Answer - D Molar conc. of HCl `= 10^(-8)`. `:.` pH = 8. But this cannot not be possible as pH of an acidic solution can not be more than 7. So we have to consider `[H^(+)]` coming from `H_(2)O`. Total `[H^(+)] = [H^(+)]_(HCl) + [H^(+)]_(H_(2)O)` IOnisation of `H_(2)O : H_(2)O rarr H^(+) + OH^(-)` `K_(w) = 10^(-14) = [H^(+)][OH^(-)]` Let x be the conc. of `[H^(+)]` from `H_(2)O` or `[H^(+)] = x [OH^(-)]_(H_(2)O)` `:. 10^(-14) = (x + 10^(-8))(x)` or `x = 9.5 xx 10^(-8) M` `:. [H^(+)] = 10^(-8) + 9.5 xx 10^(-8) = 10.5 xx 10^(-8)` or pH `= -log(10.5 xx 10^(-8)) = 6.98` |
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