# chem

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sample of 1.00g of BaSO4 and a similar sample of 1.00g of CaSO4 were added to water at 25 Celsius to give 1L of solution. Calc. the concentration of Ba2+, Ca2+, and SO4^2- ions present in the solution?

• chem -

What Ksp values are you using for BaSO4 and CaSO4?

• chem -

It doesn't give anything else except what i wrote

• chem -

Right, however, look in the tables in your text (usually in the back in the appendix) and you will find Ksp (solubility products) listed. Those are the numbers I need. Why can't I look them up? I can but tables don't agree and I want to use the same numbers you must use.

• chem -

i was given the same problem...my text gives the Ksp of BaSO4= 1.1x10^-10. but not the Ksp of CaSO4

• chem -

Ksp: BaSO4: 1.1*10^-10
CaSO4: can't find it

• chem -

OK. I will assume the Ksp for CaSO4 is about 1E-4. The values I can find on the web aren't quite that but it makes the problem a little easier. Since you can't find it in your tables, I assume the problem is saying that 1.00 g CaSO4 is soluble in 1 L solution. If that is not a good assumption this won't be the right way to work the problem.
(CaSO4) = 1.00/molar mass CaSO4 = about 0.00734M
.........CaSO4 --> Ca^2+ + SO4^2-
.........solid....0.00734..0.00734
That gives the Ca^2+ and SO4^2-.

Then BaSO4 --> Ba^2+ + SO4^2-
I....solid.....0........0
C....solid.....x........x
E....solid.....x........x

Ksp BaSO4 = (Ba^2+)(SO4^2-)
(Ba^2+) = x from BaSO4
(SO4^2-) = x from BaSO4 and 0.00734 from CaSO4
Plug into Ksp for BaSO4 and solve for x = (Ba^2+).