Question

For each of the salts on the left, match the salts on the right that can be compared directly, using K_sp values, to estimate solubilities.

(If more than one salt on the right can be directly compared, include all the relevant salts by writing your answer as a string of characters without punctuation, e.g, ABC.)

	1.	silver carbonate		A. PbCl2
	2.	copper(II) sulfide		B. Mn(OH)2
				C. AgCN
				D. Cu(OH)2

Write the expression for K in terms of the solubility, s, for each salt, when dissolved in water.

silver carbonate			copper(II) sulfide
Ksp =			Ksp =

Note: Multiply out any number and put it first in the K_sp expression. Combine all exponents for s.

***** 1 & 2 COULD HAVE MORE THAN 1 ANSWER*****

Answer 1

Solubility of AB, A2B, AB2, A3B, AB3, A2B3, A3B2

For solubility comparisson:

AB <-> A+ + B-; Ksp = [A+][B-] = S*S = S^2 --> S = sqrt(Ksp)

A2B <--> 2A+ + B-2 Ksp = [A+]^2[B-2] = (2S)^2 * S = 4*S^3 --> S = (Ksp/4)^(1/3)

AB2 <--> A+2 + 2B- ; Ksp = [A+2][B-]^2 = S* (2S)^2 = 4*S^3 --> S = (Ksp/4)^(1/3)

A3B <---> 3A+ + B-3 ; Ksp = [A+]^3[B-3] = (3S)^3 * S = 27*S^4 --> S = (Ksp/27)^(1/4)

AB3 <--> A+3 + 3B- ; Ksp = [A+3][B-]^3 = S* (3S)^3 = 27*S^4 --> S = (Ksp/27)^(1/4)

A3B2 <-->3A+2 + 2B-3; Ksp = [A+2]^3[B-3]^2 = (3S)^3 * (2S)^2 = 108*S^5 --> S = (Ksp/108)^(1/5)

A2B3 <-->2A+3 + 3B-2; Ksp = [A+3]^2[B-2]^3 = (2S)^2 * (3S)^3 = 108*S^5 --> S = (Ksp/108)^(1/5)

PbCl2 = AB2; Mn(OH)2 = AB2; AgCN = AB; Cu(OH)2 = AB2

Silver cabronate = Ag2CO3 --> A2B type salt,

then, A2B salts can be compared only with A2B and AB2 salts, which are:

PbCl2 = AB2; Mn(OH)2 = AB2; Cu(OH)2 = AB2

Now, for

Copper (II) Sulfide = CuS, this is type AB

then, only

PbCl2 = AB2; Mn(OH)2 = AB2; AgCN = AB; Cu(OH)2 = AB2

AgCN will do

Q2

for

Ag2CO3

Ksp = [Ag+]^2[CO3-2]

and for

CuS ---> Cu2+ + S2-

Ksp = [Cu2+][S2-]