Question

Hydroxylamine, NH2OH, is a weak base. A 0.010 M solution of hydroxylamine has a pH of 8.98. What is the Kb for this compound? A. 9.5 x 10-6 B. 3.1 x 10-3 C. 1.7 x 10-5 D. 9.1 x 10-11 E. 9.1 x 10-9

Answer 1

Hydroxylamine, NH2OH, is a weak base. A fraction of molecules in aqueous solution accepts proton from water:

               NH2OH (aq) + H2O (l) ↔ NH3OH+ (aq) + OH– (aq)

               0.010 M solution of hydroxylamine

                PH of hydroxylamine =8.98

pH = 14 – ½ × pKb + ½ × log [B]

8.98 = 14 – ½ × pKb + ½ × log 0.010

8.98 = 14 – ½ × pKb + ½ − 2

  ½ × pKb = 14 – 1 – 8.98

    pKb = 4.02 x2 = 8.04

    −log kb = 8.04

Kb = 10^−8.04   = 9.12 x 10⁻⁹

Kb = 9.12 x 10⁻⁹