InterviewSolution
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InterviewSolution
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20 ml of 0.5 N HCl and 35 ml of 0.1 NaOH are mixed. The resulting solution willA. Be neutralB. Be basicC. Turn phenolphthalein solution pinkD. Turn methyl orange red |
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Answer» Correct Answer - D (i) 20 ml of 0.5 N HCl `0.5 N rArr 1000 m` 0.5 mole HCl is present in 20 ml `= (20 xx 0.5)/(1000) = 1.0 xx 10^(-2)` (ii) 35 ml of 0.1 NaOH `0.1 N rArr 1000 ml` of 0.1 mole NaOH is 35 ml `= (35 xx 0.1)/(1000) = 0.35 xx 10^(-2)` `rArr (1.0 - 0.35) 10^(-2) = 0.65 xx 10^(-2)` mole HCl `HCl = H^(+) + Cl^(-) rArr [HCl] = [H^(+)] + [Cl^(-)]` 55 ml contains `0.65 xx 10^(-2)` mole of `H^(+)` ions `1000 ml - (0.65 xx 10^(-2) xx 10^(3))/(55) = (6.5)/(55)` `pH = -log [H^(+)] = -log (6.5//55)` `= log 55 - log 6.5 = 9.2` Due to acidic nature of solutions the colour of methylorange becomes red. |
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