Question

Rank the following salts in order of increasing molar solubility. Salt Ksp AgSCN 1.0 × 10–12 Ag2CrO4 1.1 × 10–12 Ag3PO4 1.0 × 10–16

Answer 1

1)

The salt dissolves as:

AgSCN <----> Ag+ + SCN-

   s s

Ksp = [Ag+][SCN-]

1*10^-12=(s)*(s)

1*10^-12= 1(s)^2

s = 1*10^-6 M

2)

The salt dissolves as:

Ag2CrO4 <----> 2 Ag+ + CrO42-

   2s s

Ksp = [Ag+]^2[CrO42-]

1.1*10^-12=(2s)^2*(s)

1.1*10^-12= 4(s)^3

s = 6.503*10^-5 M

3)

The salt dissolves as:

Ag3PO4 <----> 3 Ag+ + PO43-

   3s s

Ksp = [Ag+]^3[PO43-]

1*10^-16=(3s)^3*(s)

1*10^-16= 27(s)^4

s = 4.387*10^-5 M

The compounds in increasing order of solubility are:

AgSCN whose solubility is 1*10^-6 M

Ag3PO4 whose solubility is 4.387*10^-5 M

Ag2CrO4 whose solubility is 6.503*10^-5 M