I just have two questions that i need help with. It seems like a lot but its rea
ID: 850471 • Letter: I
Question
I just have two questions that i need help with. It seems like a lot but its really not i just had to explain what I did in my experiment. The answers are at the end. Here was the experiment that I did.
Complete the table and the concentrations. Identify which cell did not have any precipitate. So I finished the table above and cells A4, A5, A6, and A7 did not have precipitate. I am guessing because over time it became too diluted.
This is what I have in each well: I have 5 drops of Ca(NO3)2(calcium nitrate) in well A1. Then I put 4 drops of distilled water in wells A2 through A7. Then i used a pipet and added about a drop from well A1 to well A2. Then mixed, then added 1 drop from well A2 to well A3, then mixed, and so on. This caused it to become very diluted over time which is why there was less precipitate in the end. They are now progressively diluted by 1/5. Then after that, I added 1 drop of Na2C2O4(sodium oxalate) to each well. This caused the precipiate to form.
I got quite a bit of precipitate in wells A1 and A2, and only a little bit in well A3.
Here are my two questions I need help with please. Thanks!!
1. Calculate the concentrations of Calcium and oxalate ions in the first well without any precipitate.
Use these concentrations to determine the solubility product constant of CaC2O4.
2. How would temperature affect your solubility results? How would the addition of a common ion affect your results? Explain
Well A1 A2 A3 A4 A5 A6 A7 Initial Concentration (M) Ca(NO3)2 0.1 0.02 0.004 0.0008 0.000016 0.0000032 0.00000064Explanation / Answer
The baalanced chemical equation is as follows:
1) Ca(NO3)2 + Na2C2O4 = 2NaNO3 + CaC2O4
So calcium nitrate reacts with sodium oxalate in 1:1 molar ratio.
Thus, before precipitate formation in the first well, calcium concentration = 0.1 M = oxalate concentration
Solubility product, Ksp = [Ca++][C2O4--] = 0.1 x 0.1 = 0.01
2) CaC2O4 = Ca2+ + C2O42-
Common ion effect will increase the cocentration of ions, hence the equlibrium will shift to the left, this will inhibit dissociation of the product, so the solubiity product will decrease.
How temperature affects solubility product, depends on the compound in question. For CaC2O4, Ksp decreases with increasing temp.