Solubility Product and Solubility of a Sparingly Soluble Salt

In this video created by Chemistry Guru, Singapore's leading JC Chemistry tuition centre, we want to discuss how to determine solubility of a sparingly soluble salt from its solubility product K_sp.

But first we need to establish the fact that K_sp and solubility are both related to a saturated solution.

Solubility Product K_sp and Saturated Solution

When a salt dissolves and the solution is diluted, the concentration of ions is expected to continue to increase.

This means the system is not at equilibrium and equilibrium constant K_sp is not relevant for a diluted solution.

When the solution is saturated, the concentration of ions is at its maximum and constant.

Hence the system is now at equilibrium and K_sp is relevant for a saturated solution.

Solubility and Saturated Solution

Solubility is the amount of salt that dissolves to give a saturated solution.

Therefore solubility is directly related to a solution that is saturated.

Since both K_sp and solubility are related to a saturated solution, this means K_sp and solubility are related to each other, and we can use one of the value to find the other.

Dissocation of Sparingly Soluble Salt CaF₂

Let's use CaF₂ as an example.

When CaF₂ is put in a beaker of water, it'll dissociate partially to form Ca²⁺ and F^- ions.

We can represent this using the following equation.

If we let x be the solubility of CaF₂, x moles of CaF₂ will dissolve to give a saturated solution which contains x moles of Ca²⁺ and 2x moles of F^-.

We can now write out the solubility product and express this in terms of solubility x to work out the relationship between K_sp and x.

This means that if K_sp is given, we can determine solubility of the salt, and vice versa.

For the detailed step-by-step discussion on how to determine solubility of a sparingly soluble salt from its solubility product K_sp, check out this video!

We can also compare ionic product and solubility product to determine if there is precipitation for that sparingly soluble salt.

Topic: Solubility Product, Physical Chemistry, A Level Chemistry, Singapore

Back to other previous Physical Chemistry Video Lessons.

Found this A Level Chemistry video useful?

This free chemistry video lesson is brought to you by Chemistry Guru, Singapore's reputable A Level Chemistry tuition centre since 2010.

Please like this video and share it with your friends!

Join my 18,000 subscribers on my YouTube Channel for new A Level Chemistry video lessons every week.

Check out other A Level Chemistry Video Lessons here!

Need an experienced tutor to make Chemistry simpler for you?

Do consider signing up for my A Level H2 Chemistry Tuition classes at Bishan or online chemistry classes!