Le Chatelier's Principle

Tutor: None Selected Time limit: 1 Day

Magnesium hydroxide is only very slightly soluble in water. The reaction by which it goes into so­lution is: Mg(OH)2 (s) ⇌ Mg2+ (aq) + 2 OH- (aq) 

It's possible to dissolve significant amounts of Mg(OH)2 in solutions in which the concentration of either Mg2+ or OH- is very, very small. Explain, using Ksp, why this is the case. 

Explain why Mg(OH)2 might have very appreciable solubility in 1 M HCl.

Oct 3rd, 2015

Thank you for the opportunity to help you with your question!

For the first part of your question:

Mg(OH)2 (s) ⇌ Mg2+ (aq) + 2 OH- (aq) 

This means that if the concentration of Mg2+ or OH- is very very small in the solution, we can assume that their product will be much less than the Ksp, where

Ksp = Conc(Mg2+)*Conc(OH-)*Conc(OH-)/(Conc(Mg(OH)2)

So, to maintain Ksp constant(which is a requirement), the concentration of Mg2+ or of OH- needs to increase, hence it's possible to dissolve significant amounts of Mg(OH)2

For the second part of your question:

HCl ⇌ H+ + Cl-

H+ + OH- ⇌ H2O

The H+ ions react with the OH- ions formed from the dissolution of Mg(OH)2, which leads to a decrease in the concentration of OH- ions. This decreases the value of Ksp, so to maintain Ksp as constant, the concentration must increase, and hence Mg(OH)2 might have very appreciable solubility in 1 M HCl.

Please let me know if you need any clarification. I'm always happy to answer your questions! :)
Sep 22nd, 2015

Studypool's Notebank makes it easy to buy and sell old notes, study guides, reviews, etc.
Click to visit
The Notebank
Oct 3rd, 2015
Oct 3rd, 2015
Mar 23rd, 2017
Mark as Final Answer
Unmark as Final Answer
Final Answer

Secure Information

Content will be erased after question is completed.

Final Answer