Question

a refrence book lists the following overall formation constants for the combination of bromide with pb2+ : log β1 = 1.77, log β2= 2.6 , log β3= 3.0 , log β4= 2.3 what are the stepwise reactions and associated formation constants?

Answer 1

stepwise reactions:

Pb+2 + Br- ---------------------> PbBr+ , β1 = 1.77 (foramtion constant)

PbBr+ + Br- --------------------> PbBr2 , β2= 2.6 (foramtion constant)

PbBr2 + Br- --------------------> PbBr- , β3= 3.0 (foramtion constant)

PbBr- + Br- ------------------> PbBr-2 , β4= 2.3 (foramtion constant)

formation constant

Kf = β1 x β2 x β3 x β4

log Kf = log β1 + log β2 + log β3 + log β4 = 1.77 + 2.6 + 3.0+ 2.3

log Kf        = 9.67

overall Kf = 4.67 x 10^9