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At what pH is Zn(OH)2 completely dissolved in water?  

September 5, 2008

I am master student of Chemical engeenering, I want to know, at what pH value Zn(OH)2 completely dissolved in the water.
Thank

Nanik Hendrawati
student - Tainan, Taiwan

Hi, Nanik. There are usually no simple and definitive answers to such questions. The solubility curve for zinc vs. pH is basically parabolic though, with a minimum at about a pH of 10.3-10.5, so you need to go well above that. Obviously you can "completely dissolve" a very small amount in a very large amount of water even at 10.3-10.5, and you cannot "completely dissolve" a large amount in a very small quantity of water at any pH.

Can you please tell us what the real question is that motivates this subquestion?

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey

... or you need to go to a much lower pH. At the high pH it will give zincate, at the low pH it will give a straight zinc salt (which salt depends on which acid is used to give the low pH).

Bill Reynolds    consultant metallurgist Ballarat, Victoria, Australia