Question

A certain weak base has a Kb of 8.50 × 10-7. What concentration of this base will produce a pH of 10.38?

Answer 1

pH = 10.05

pOH = 3.95

[OH-] = 10^-pOH = 10^-3.95 = 0.00011220 M

B + H2O <==> HB+ + OH-

Kb = ([HB+] [OH-]) / [B]

8.50 x 10^-7 = [(1.122 x 10^-4) (1.122 x 10^-4)] / x

x = 0.0148 M

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