Le Châtelier's principle states that if a stress is applied to a system at equilibrium, the system will shift to relieve that stress. This is true for all types of equilibrium, including the dissolution of salts that are only sparingly soluble. Here is the chemical reaction that represents solid barium sulfate dissolving in water: BaSO4(s) ⇌Ba2+(aq)+SO42−(aq) Ksp =1.1×10−10

Which of the following actions would shift this reaction toward solid barium sulfate?

Add more barium sulfate. Add more sulfate ions. Remove sulfate ions. Remove barium ions.

In which of the following would barium sulfate be least soluble?

pure water

1 M NaNO3

1 M K2SO4

Le Châtelier's principle states that if a stress is applied to a system at equilibrium, the system will shift to relieve that stress and attain the equilibrium again.

Add more sulfate ions will increase the concentration of the products side, so the reaction will be shifted towards the reactants side to relieve the stress and attain the equilibrium again.

So, the right choice is: Add more sulfate ions.

2) In which of the following would barium sulfate be least soluble?

The answer is 1 M K₂SO₄, it has a common ion effect of SO₄⁻ ions that increase the concentration of the products side, so the reaction will be shifted towards the reactants side to relieve the stress and attain the equilibrium again.

So, the solubility will decrease.