(adsbygoogle = window.adsbygoogle || []).push({}); Ksp of Calcium Hydroxide - A Percentage Error of 480%??

1. The problem statement, all variables and given/known data

I did a titration between HCl and Ca(OH)2. I use the indicator Phenopthalein I did most of my calculations and thru repeated checking cannot find any significant error in my calculations.

However, upon calculating the percentage error of this experiment, I got a whooping 488% error! I have no idea what kind of errors would cause such as huge percentage. I have never seen such a huge percentage myself.

2. Relevant equations

C = n/v to first calculate moles of HCl (C = 0.05 M)

Mole ratios to find moles of Ca(OH)2

C= n/v again to find concentration of Ca(OH)2

that would also be concentration of Ca2+ ions

x2 of concentration to find concentration of OH- ions

Ksp = [Ca][OH]^2

3. The attempt at a solution

These are my calculations and the data...

19 ml of HCl with concentration of 0.05 M

25 ml of Ca(OH)2

Setting up a titration between them using phenolpthalein in Ca(OH)2. HCl is dripped into the flask till pink color of pheno appears.

So calculations, I find out HCl moles is = 9.75 x 10^-4 mols

and thru stoichiometry, we find out Ca(OH)2 has half of that, 4.875 x 10^-4

and calculating that, concentraition of Ca(OH)2 is 0.01948 M

So Ca2+ concentration is 0.0198M

and

OH- concentration is double that, so 0.0389M

Setting up Ksp = [Ca][OH]^2

Ksp = 2.95 x 10^-5

Accepted Value* for Ksp of Ca(OH)2: 5.02 x 10-6

% error = ((experimental value – accepted value) / (accepted value)) x 100%

= 488%

What possible errors would cause such a huge percentage?

Acid or base was left on the sides of the flask, or at the tip of the burette used, measurement errors, air bubbles etc. should be relatively minor errors right?

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# Homework Help: Ksp of Calcium Hydroxide - A Percentage Error of 480%?

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