Anilinium ion has pKa = 4.6 at 298 K. Using the weak-base approximation [OH-]=sqrtK_b c, the pH of a 0.1 M aqueous solution of aniline is closest to

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Anilinium ion has pKa = 4.6 at 298 K. Using the weak-base approximation $[OH X^{-}] = K_{b} c$ , the pH of a $0.1 M$ aqueous solution of aniline is closest to

p K_{b} = 14 - 4.6 = 9.4

pOH = \frac{1}{2} (9.4 + 1) = 5.2

, so

pH = 14 - 5.2 = 8.8

(base-water ionisation is far larger than water autoionisation, so the approximation holds).