[howsockgothappy]

Hi, so I'm trying to do the calculations to go with our lab and am experiencing some confusion. It asks to determine the solubility of Ca(OH)₂ using your titration data... Seems easy enough, I calculated the H⁺ moles from the amount of HCl used, set that equal to moles OH^- since the titration should have been at the quivalence point, calculated concentration of OH^- and then used that to calculate concentration of CA²⁺. I was pretty certain that using these I should be able to get the right answer for K_sp, and I did get sort of in the general ballpark.

My confusion comes at the end, where it asks for total concentration of OH^- vs. the concentration of OH^- provided by Ca(OH)₂... I don't see how that fits into the calculations, or even how I can do that. It's Ca(OH)₂ and HCl, so shouldn't the calcium hydroxide be the ONLY source of OH^-?

[AWK]

For Ca(OH)₂ you can safely neglect OH^- ions from water autoprotolysis.