1.

Boric acid `Br(OH)_(3)` is monobasic Lewis acid if gives `H^(+)` ions in aquoeus soluions as follows `B(OH)_(3) + H_(2)O hArr [B(OH)_(4)]^(-) + H^(+)` `K_(a) = 5.9 xx 10^(-10)` The `P^(H)` of `0.025M` aqueous solution is `[log 5.9 = 0.771]`A. `5.42`B. `4.52`C. `2.45`D. `4.675`

Answer» Correct Answer - A
`P^(H) = - 1/2 [Log K_(a) + logC]`
`= - 1/2["log"(5.9 xx 10^(-10)) + "log" (0.025)]`
`= - 1/2[(-10 + "log"5.9) + (-2 + "log" 2.85)]`
`= - 1/2[(-10 + 0.771 )+ (-2 + 0.3979)]`
`= - 1/2[(-9229) + (-16021)]`
`= - 1/2 [-9.229 - 1.6021]`
`=- 1/2[-10.3811] = 5.4255`


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