Molar Solubility Ksp

The Common Ion Effect

How do we solve these questions?

Steps

1. Write out the Ksp equation

2. Complete an ICE table

3. The common ion will be s (or x) + the concentration given

4. The other ion will be an unknown as per the mole ration given by the equation

5. Solve for the unknown to calculate the molar solubility

6. State the effect on solubility

Practice Question

The value of Ksp for silver iodide is 8.52 x 10^-17. Calculate the molar solubility of:

a) silver iodide in water and;

b) in 1.5mol L^-1 potassium iodide solution.

Multiple Choice

The answer to a) is:

• 9.23 x 10^-9 M

• 4.26 x 10^-17

• 7.26 x 10^-33

• 2.92 x 10^-17

Multiple Choice

The answer to b) is:

• 5.68 x 10^-17

• 1.3 x 10^-16

• 6.15 x 10^-9

• 1.38 x 10^-8

Multiple Choice

How much more soluble is silver iodide in water than in 1.5M potassium iodide solution?

• 162.5 million times

• 162.5 times

• 1650 times

• 162500 times

Multiple Choice

Which direction will the reaction favour with the addition of potassium iodide?

• reverse

• forward

Multiple Choice

Is the solubility increased or decreased with the addition of potassium iodide?

• decreased

• increased