# How do you solve the Ksp equations?

##### 2 Answers

They all follow a basic pattern, which I will describe and demonstrate below...

#### Explanation:

To illustrate the method, I will use a generic insoluble solid

When dissolved in water, our compound dissolves according to

The

Here's the solution:

First, let the variable

First, since each formula unit of

Similarly, each unit of

Placing these variables into the

To solve this, note that

Divide each side by 4, then take the cube root:

This means the solubility is

Ksp is a particular form of Equilibrium in solution. Use an I.C.E. chart (Initial, Change, Equilibrium) to correctly determine the quantities of reactants and products before using th equations.

#### Explanation:

Some simpler solutions may be calculated directly. For example, to find the concentration of aluminum ion inn equilibrium with hydroxide, given the Ksp.

Using the given value of the hydroxide ion concentration, the equilibrium concentration of aluminum ion is:

The other way – finding the Ksp from the solubility – is just a rearrangement of the equation.

The molar solubility of

For

For every mole of