the solubility product constant (Ksp) of ca(oh)2 at 25 C is 4.42*10^-5. a 500 ml of saturated solution of ca(oh)2 is mixed with equal volume of .4M naoh. what mass of ca(oh)2 is precipitated?

2 answers

You really need to find the caps key on your keyboard and use it. First, calculate the solubility, S, in the saturated solution of Ca(OH)2. That is
......Ca(OH)2==>Ca^2+ + 2OH^-
I.....solid......0.......0
C.....solid......S.......2S
E.....solid......S.......2S
Plug the E line into Ksp expression and solve for S. This gives you the solubility of Ca(OH)2 in a saturated solution in mols/L. Convert to grams/L with grams = mols x molar mass = ?g

Then we add 500 mL 0.4M NaOH.
(NaOH) = 0.4M x (500/1000) = 0.2M.
We solve the expression again for S but this time with the added NaOH.
.....Ca(OH)2 ==> Ca^2+ + 2OH^-
I....solid.......0......0.2M
C....solid.......S........2S
E....solid.......S......2S+0.2

Plug the E line into Ksp expression and solve for S.
Convert to grams.
How much ppts? You know the solubility with no NaOH and you know the solubility with NaOH (it will be less). Subtract to find grams that ppt. Post your work if you get stuck.
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