Question

Calculate the solubility of LaF3 in grams per liter in:

a) pure water

b) 0.025 M KF solution

c) 0.150 M LaCl3 solution

Answer 1

From tables, we know:

and

Also:

The expression of solubility product is:

If we increase the concentration of the products, the equilibrium move towards left, and it will decrease the solubility.

a)

  

b)

  

or

You can see, in the first question, S is very small. So, we can assume 3S<<0.025

c)