Question

A solution of Na2SO4 is added dropwise to a solution that is 1.1×10⁻² M in Ba2+ and 1.1×10⁻² M in Sr2+.

The solubility-product constants are as follows:

BaSO4:SrSO4:KspKsp==1.1×10−103.2×10−7

You may want to reference(Pages 751 - 753) Section 17.6 while completing this problem.

Which cation will precipitate first?

Ba2+ precipitates first.

Sr2+ precipitates first.

What concentration of SO42− is necessary to begin precipitation? (Neglect volume changes.)

Express the molarity to two significant digits.

1.0×10−8

M

***Need help with this answer.

1.) At what concentration of SO42− will the second cation begin to precipitate?

Express your answer using two significant figures.

Answer 1

Answer:

Given,

To determine [SO42-]

consider,

Ksp = [Ba²+] [SO4^2-]

1.1x10^-10 = [0.011 M] [SO4-]

On solving we get,

[SO4--] = 1 x10^-8 M.

Now,0

Ksp = [Sr²⁺] [SO4^2-]

3.2*10^-7 = 0.011 [SO4^2-]

On solving we get concentration

i.e.,

[SO4^2-] = 2.91 x10^-5 M.

Hence,the precipitation will start to occur at [SO4^2-] = 1 x10^-8 M.