a 0.252g sample pf inknown organic base is dissolved in water n titrated with a 0.14M HCl sol. aftr d addition f 20 ml acid,a pH of 10.7 is recorded. the equivalence pt. is reached at 40 ml HCl. acid n base combine in 1:1.find kb of base??

Dear student,

Ka = [H⁺] * [A^-] / [HA]

Rearrange to give [H⁺(aq)]:

[H⁺] = Ka * ([HA] / [A^-])

Take log10 of both sides:

log[H⁺] = log(Ka) + log([HA] / [A^-])

Multiply both sides by -1:

-log[H⁺] = -log(Ka) - log([HA] / [A^-])

Recognizing that -log[H⁺] is pH, and -log(Ka) is pKa

pH = pKa - log([HA] / [A^-])

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All the best.

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Sagar Singh

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