[Faisal]

I had this question in my exam and I dont get it at all.Can anyone plz tell me the answer and explain.Thank u.
What is the effect of adding NAOH to an equilibrium system containing a saturated Mg(OH)2 solution?
A-Less Mg(OH)2 dissolves
B-more Mg(OH)2 dissolves
C-Mg(OH)2 dissolves completely
D-No effect on the amount of Mg(OH)2 that dissolves
E-Mg(OH)2 does not dissolve at all

[AWK]

and your attempt is ?

[Faisal]

I dont get the question at all.And since there is double penalty in my exam...I juz left it...din wanna risk it.
I think since Mg+OH_<-^->-MG(OH)2 is te eqlbr equation.Therefore adding more NaOH shud shift the eqlbr more to the right...so I go for E.Is tht correct?

[AWK]

Hint How common ion effect influences on solubility of Mg(OH)2

[Faisal]

yeah so it shifts the eqlbr position to the right...answer is E...right?

[Borek]

yeah so it shifts the eqlbr position to the right...answer is E...right?

No. As you wrote - equilibrium SHIFTS. It doesn't mean nothing dissolves at all.

[Arkcon]

yeah so it shifts the eqlbr position to the right...answer is E...right?

No. As you wrote - equilibrium SHIFTS. It doesn't mean nothing dissolves at all.

This is an important thing to remember when faced with a multiple choice question.  It's of course best if you know the correct answer, but you can get there by excluding the impossible ones, to narrow down your search.  Then once you've gotten the answer correct, you can look up the reason.

You know that the equilibrium will shift.  But you know it's an equilibrium, therefore E isn't correct, and likewise C can't be correct, nor D ...

And now you've leaned something else, a shift in equilibrium doesn't have absolute, all or nothing results.  That's important to remember, because the next time you see a question of this type, it will likely be slightly different.

[Faisal]

OHHHHHHHHHHHHH...I get it now...the whole 'saturated' thing isn't important...thank you so much...so the answer is A...right?

[Borek]

Yep.