The pH of a 0.15 M butylamine, C&H3NH2 solution is 12.0 at 25°C. Calculate the dissociation constant of the base.

The dissociation  constant of the base : 7.4 x 10⁻⁴

Butylamine, C4H9NH2 Is A Weak Base

Kb is the dissociation  constant of the base.

LOH (aq) ---> L⁺ (aq) + OH⁻ (aq)  

[OH⁻] for weak base can be formulated :

pH of solution : 12

pH+pOH=14, so pOH :

14-12 = 2, then :

the the dissociation  constant (Kb) =

Or you can use from ICE method :

C4H9NH2(aq) + H2O(l) ⇌ C4H9NH3+(aq) + OH-(aq)

0.15

x                                                x                        x

0.15-x                                        x                        x

14 days is the half-life of phosphorus-32