1. The problem statement, all variables and given/known data I have to calculate the Ksp value for calcium hydroxide from experimental data. We titrated 10.00 mL of saturated Ca(OH)2 aqueous solution with 11.00 mL of 0.01607 M EDTA. 2. Relevant equations The Ksp formula is given in my manual as [Ca^2+]*[OH^-]^2 3. The attempt at a solution I got the # of moles of EDTA by multiplying molarity by liters = 0.0001768 mol. Since the stoichiometric ratio of Ca^2+ to EDTA is 1:1, 0.0001768 mol of ca^2+ have been titrated. Now I divided that by 0.010 L to get the [Ca^2+] = 0.01768 M I got the OH^- concentration by multiplying 0.01768 x 2 = 0.03535 M. Using the above formula, *[0.3535]^2 = 2.209*10^-5 Herein is the problem: my book gives the Ksp as 8.0*10^-6. So my result is pretty far off, giving me a percent error of 176%. Am I doing something wrong? Did I lose a zero somewhere or is my experimental data flawed?