A) Which will precipitate first? BaCrO4 or BaC2O4
Ksp BaCrO4 = (Ba^2+)(CrO4^2-) = 2.10E-10
The BaCl2 is being added drop by drop. What must (Ba^2+) = for the first ppt of BaCrO4 to appear. That will be
(Ba^2+) = Ksp/(CrO4) = 2.10E-10/0.0492 = about 4.3E-9 M. You need to redo ALL of the calculations in this problem. My answers are just close estimates.
Do the same thing for BaC2O4. I get (Ba^+) = 2.3E-5 M. You should confirm all of these numbers. Sometimes I punch in the wrong numbers on the calculator.
Obviously the BaCrO4 will ppt first because 4.3E-9 will be reached first.
A solution containing a mixture of 0.0492 M potassium chromate (K2CrO4) and 0.0565 M sodium oxalate (Na2C2O4) was titrated with a solution of barium chloride (BaCl2) for the purpose of separating CrO42– and C2O42– by precipitation with the Ba2 cation. Answer the following questions regarding this system. The solubility product constants (Ksp) for BaCrO4 and BaC2O4 are 2.10 × 10-10 and 1.30 × 10-6, respectively.
A) Which will precipitate first? BaCrO4 or BaC2O4
B) What concentration of Ba2 must be present for BaCrO4 to begin precipitating?
C) What concentration of Ba2 is required to reduce oxalate to 10% of its original concentration?
D) What is the ratio of oxalate to chromate ([C2O42–]/[CrO42–]) when the Ba2 concentration is 0.0010 M?
4 answers
B) What concentration of Ba2 must be present for BaCrO4 to begin precipitating?
See my work on the first response. All of the calculations are there.
See my work on the first response. All of the calculations are there.
C) What concentration of Ba2 is required to reduce oxalate to 10% of its original concentration?
Initial (C2O4^2-) = 0.0565 M so 0.1 of that is 0.00565 so
(Ba^2+) = 1.3E-6/0.00565 = 0.0002 but check that.
Initial (C2O4^2-) = 0.0565 M so 0.1 of that is 0.00565 so
(Ba^2+) = 1.3E-6/0.00565 = 0.0002 but check that.
D) What is the ratio of oxalate to chromate ([C2O42–]/[CrO42–]) when the Ba2 concentration is 0.0010 M?
Use Ksp for BaCrO4, plug in 0.001 for (Ba^2+) and calculate (CrO4^-).
Do the same with Ksp for BaC2O4 and calculate C2O4^2-
Then take the ratio
Remember to confirm all of this with your calculations and your thoughts.
Use Ksp for BaCrO4, plug in 0.001 for (Ba^2+) and calculate (CrO4^-).
Do the same with Ksp for BaC2O4 and calculate C2O4^2-
Then take the ratio
Remember to confirm all of this with your calculations and your thoughts.