5. Calculate the solubility of Cu(N3)2 in water in grams per litre, where the Ksp = 6.3 x 10-10.

Equilibrium equation:

Cu(N3)2 (s) Cu2+ (aq) + 2 N3- (aq)

The goal is to use:

Ksp = [ Cu2+ ][ N3- ]2

to determine the concentration of Cu(N3)2 which can dissolve in aqueous solution.

Given that [ Cu2+ ] = x, and [ N3- ]2 = 2x, which of the following represents an appropriate substitution?

a) 6.3 x 10-10 = (x)(2)(2x) = 4x2
b) 6.3 x 10-10 = (x2)(2x) = 2x3
c) 6.3 x 10-10 = (x)(2x)2 = 4x3
d) 6.3 x 10-10 = {x} / {2} (2x) = x2