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Sunday, September 7, 2014

Solubility Product Constant Problems

Category: Chemical Engineering Math

"Published in Newark, California, USA"

A chemist dissolves BaSO4 in pure water at 25°C. If Ksp = 1 x 10-10, what is the solubility of barium sulfate in water?

Solution:

Since barium sulfate is a slightly soluble salt in water, then it is not 100% completely dissolved. Usually, if a salt is slightly soluble in water, then the solution is cloudy at most. There's also a precipitate of undissolved salt at the bottom of the solution. Ksp will tell us how soluble the salt is. If Ksp = 0, then the salt is not soluble in water at all at any temperature. If you will shake the solution, it is cloudy at first and then later all particles will precipitate at the bottom of the solution. There are some salts that are more soluble in warmer solution rather than in room temperature solution. If Ksp = ∞, then the salt is 100% completely dissolved. The solution is clear at all at any temperature. 

Let's consider the barium sulfate that is slightly soluble in water


The solubility of barium sulfate is calculated by its equation


The concentration of barium ion and sulfate ion are expressed in molarity.

Let x = be the concentration of barium ion in the solution.
      x = be the concentration of sulfate ion also in the solution.

Therefore, the solubility of barium sulfate in water is