a For each of the salts on the left, match the salts on the right that can be compared directly, using Ksp 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 iodide _ [need answer here]

2. manganese(II) hydroxide _ [need answer here]

A. Fe(OH)2

B. CaSO3

C. NiCO3

D. Ba3(PO4)2

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

silver iodide Ksp = _ [need answer here]

manganese(II) hydroxide Ksp = _ [need answer here]

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

Ksp (Solubility products) are the equilibrium constants for poorly soluble compounds. As every equilibrium constant, it is formed by the product of the products raised to their stoichiometric coefficients divided by the product of reactants raised to their stoichiometric coefficients. We only include in the constant gases and aqueous species. So, to solve this task, we need to write each reaction and its Ksp.

1. Silver Iodide

AgI(s) ⇄ Ag⁺(aq) + I⁻(aq)

When AgI is put in water, the concentration of Ag⁺ and I⁻ that actually dissolve is known as solubility (S). So the concentration of both Ag⁺ and I⁻ would be S.

AgI(s) ⇄ Ag⁺(aq) + I⁻(aq)

S S

We can replace this in the Ksp expression:

Ksp = [Ag⁺].[I⁻] = S.S = S²

We can follow the same steps to find out the relationship between Ksp and S for each compound.

2. Mn(OH)₂(s) ⇄ Mn²⁺(aq) + 2OH⁻(aq)

S 2S

In this case, the concentration of OH⁻ is 2S because 2 moles are produced along with 1 mole of Mn²⁺.

Ksp = [Mn²⁺].[OH⁻]² = S.(2S)² = 4S³

A. Fe(OH)₂(s) ⇄ Fe²⁺(aq) + 2OH⁻(aq)

S 2S

Ksp = [Fe²⁺].[OH⁻]² = S.(2S)² = 4S³

B. CaSO₃(s) ⇄ Ca²⁺(aq) + SO₃²⁻(aq)

S S

Ksp = [Ca²⁺].[SO₃²⁻] = S.S = S²

C. NiCO₃(s) ⇄ Ni²⁺(aq) + CO₃²⁻(aq)

S S

Ksp = [Ni²⁺].[CO₃²⁻] = S.S = S²

D. Ba₃(PO₄)₂(s) ⇄ 3 Ba²⁺(aq) + 2 PO₄³⁻(aq)

3S 2S

Ksp = [Ba²⁺]³.[PO₄³⁻]²= (3S)³.(2S)²= 108S⁵

a. The salts that can be compared using the same Ksp expressions are:

silver iodide BC

manganese(II) hydroxide A

b.

silver iodide Ksp = S²

manganese(II) hydroxide Ksp = 4S³