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.	lead sulfate		A. BaF2
	2.	lead bromide		B. Ag2SO3
				C. CaCrO4
				D. Pb(OH)2

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

lead sulfate			lead bromide
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)

Now, substitute al Ksp values, and identifty molar solubilities:

Lead sulfate = PbSO4 = AB type

Lead Bromide = PbBr2 = AB2 type

BaF2 = AB2 type

Ag2SO3 = A2B type

CaCrO4 = AB type

Pb(OH)2 = AB2 type

then, recall that AB2 = A2B types

from the list

PbSO4 = CaCrO4 only

for

PbBr2 = (BaF2, Ag2SO3, Pb(OH)2))

Q2.

write Ksp

Ksp = [Pb2+][SO4-2]

Ksp [Pb2+][Br-]^2