How do you solve the Ksp equations?
They all follow a basic pattern, which I will describe and demonstrate below...
To illustrate the method, I will use a generic insoluble solid
When dissolved in water, our compound dissolves according to
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.
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 every mole of