[mahi123]

Okay we did a lab to find out the Ksp for Calcium Oxalate. We reacted 5 ml(5 droplets) of 0.1 mol/L of Sodium Oxalate with 5 ml( 5 droplets) of Calcium Nitrate with varying concentration( added water). Well 1 had 0.1, then 0.05, then 0.025 so on( keep dividing by 2) upto 12 wells.
Equation is:
Ca(NO3)2 + Na2C2o4 ~~~~~~> CaC2O4 + 2NaNO3
So CaC2O4 breaks >>>> Ca + C2O4
Now my question is Ksp for Calcium Oxalate is 2.43 X 10-09. The lab question asked us to find the well which had the highest concentration of Calcium Nitrate where the precipitate did not form(#8 for us). Now if I find the Q for well 8, I get 1.9 x 10-05, which is a lot bigger than the Ksp. So I'm just confused because if Q > Ksp means the precipiate will form but in our case Q is bigger and the precipitate didn't form. For all the wells, Q comes out to be bigger, but for some precipitate formed, and for some it didn't. So I'm just confused about how to intrepret my result, I know there were some errors as we should have got the precise number or close to it, but I don't know how it changed the results if someone can help or give some hints that would be great.

[Borek]

Have you controlled solution pH or not? Oxalic acid is a weak one..

[enahs]

I have never met a dropper in a chem-lab that drops 1-mL per drop, not even close. In my experience 5 drops is typically not even a mL.

[mahi123]

Have you controlled solution pH or not? Oxalic acid is a weak one..

I don't think we had to do anything with the pH.

I have never met a dropper in a chem-lab that drops 1-mL per drop, not even close. In my experience 5 drops is typically not even a mL.

lol, what I meant was that we could assume 1 drop as 1 mL or even L it doesn't matter, just to do the ratio to calculate final concentrations etc. Anyway, I've completed my lab report, the Ksp value is a lot bigger for the whole class, but in actual it's 2.3 x 10-09 so I guess some sources of error and the teacher wants us to talk about them.

[Borek]

Have you controlled solution pH or not? Oxalic acid is a weak one..

I don't think we had to do anything with the pH.

I guess some sources of error and the teacher wants us to talk about them.

What happens to weak acids in water solution?