[cath651]

In the lab, I did a titration of saturated calcium hydroxide solution with a standardized solution of HCl (0.01114M).
10.00mL of the saturated Ca(OH)₂ solution was mixed with 25 mL of distilled water and two drops of bromothymol blue.

The average volume of HCl used is 37.63mL. I found the moles of H⁺ by multiplying 0.03763L by the molarity of HCl, 0.01114M.

Ca(OH)₂ + 2HCl ---> CaCl₂ + 2H₂O
    1       :   2
To find the moles of OH^-, I divided the moles of H⁺ by 2

But to find the molarity of OH^-, do I need to divide the moles of OH^- by the total volume (72.63mL) or by the volume of Ca(OH)₂ (10.00mL)?

To find the molarity of Ca²⁺, I would divide the molarity of OH^- by 2 since there are 2 moles of OH^- per mole of Ca²⁺
I would then find Ksp = [Ca²⁺][OH^-]²

[Borek]

But to find the molarity of OH^-, do I need to divide the moles of OH^- by the total volume (72.63mL) or by the volume of Ca(OH)₂ (10.00mL)?

You need molarity of OH^- in the original solution. You determine number of moles of OH^-. If you divide it by anything else then the oiginal volume, you get some unrelated number.

[Pradeep]

Up to moles of H+ u ar correct. Then H+ : OH- = 1:1 always.

But H+ : Ca 2+ = 1:2

So u shud divide number of H+ moles by 2 and then by volume (10.00 ml).  Bcoz u ar going to find the conc of saturated solution. so u shud calculate the conc of OH - in that solution.

[OH-] = 0.04192

Then [Ca2+] = 0.02095

then Ksp = 1.8416 * 10^-5 mol^-3 dm

[Borek]

Bcoz u ar going to find the conc

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