InterviewSolution
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InterviewSolution
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When one drop of a concentrated `HC1` is added to `1L` of pure water at `25^(@)C`, the `pH` drops suddenly from `7` to `4`. When the second drop of the same acid is added, the `pH` of the solution further drops to aboutA. `0`B. `1.0`C. `2.0`D. `3.7` |
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Answer» Correct Answer - D When `pH = 7, [H^(o+)]` initial `=10^(-7)M`. When `pH = 4, [H^(o+)]` Total `=10^(-4)M`. `:. [H^(o+)]` added from `HC1 = (10^(-4) - 10^(-7))` `=10^(-4) (1-0.001)~~ 10^(-4)M`. When another drop of `HC1` is added: When `pH = 4, [H^(o+)] "initial" = 10^(-4)M` `:. [H^(o+)] added ~~ 10^(-4)` `[H^(o+)] Total = (10^(-4)+10^(-4)) = 2 xx 10^(-4) M` `:.pH =- log (2 xx 10^(-4)) =- 0.3 + 4 = 3.7` Note: Change in volume on adding one drop of `HC1` is assumed to be negligible. |
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