Question

consider the following equilibrium:

Mg(OH)2(aq) <-> Mg2+ (aq) + 2OH-(aq)

a) what would happen to the equilibrium if some acid is added to the soultuion?
--->OH- would increase causing Mg(OH02 to dissolve

b) what would happen to the solubility of Mg(OH)2?
---> it would increase

c) what would happen to the Ksp?
--> I don't know about this part??

Answer 1

I want to quibble a little with your answers. Technically a is incorrect because you are talking about OH and the question is asking what happens to th equilibrium. I would like to see you say that the equilibrium will shift to the right. You are correct that Mg(OH)2 will dissolve. Also, I wonder if you missed the point with adding acid. Adding H3O^+ to OH^- causes the reaction H3O^+ + OH^- ==> 2H2O to occur. That REMOVES OH- so the Mg(OH)2 reaction you show shifts to the right in order to REPLACE the OH^- that has been removed by the acid.

Your answer to b is right.

c. Ksp does not change (unless temperature changes, either up or down). That's why we can use Ksp in these calculations because, at constant T, K is constant.