Question

Find the Concentration of CrO4^2- in 0.0033M Ba(NO3)2 saturated with BaCrO4. Include activity coefficients in your solubility-product expression. Ksp of BaCrO4 = 1.17 x 10^-10

I have no idea what to do to solve this :(

Answer 1

Calculate ionic strength of 0.0033M Ba(NO3)2. Then calculate activity coefficient (or some books have a table that can be used).

Then [(Ba^2+)*fBa] x [(CrO4^2-)*fCrO4] = Ksp = 1.17E-10
Substitute (Ba^2+) = 0.0033M + x
for (CrO4^2-) substitute x
Substitute fBa and fCrO4 and solve for x.

Answer 2

Thank you for answering! I got .0099 for the ionic strength. I just don't understand how to calculate the activity coefficient though. We just learned the concept and I'm confused.