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## Homework Statement

1. A 1L solution contains 0.1M of each Pb

^{+2},Ca

^{+2}, and Sr

^{+2}. Which ion precipitates last as Na

_{2}SO

_{4}is slowly added with no change in volume?

2. What is the concentration of the ion that precipitates first when the second ion precipitates?

Given:

Ksp PbSO

_{4}=1.8x10^-8

Ksp CaSO

_{4}=7.1x10^-5

Ksp SrSO

_{4}=3.4x10^-7

## Homework Equations

## The Attempt at a Solution

1. Pb2+ precipitates first as it has the lowest Ksp value.

2. This is where i get stuck. I know SrSO4 is the second ion to precipitate. I get:

ksp=[Sr

^{2+}][SO

_{4}

^{2-}]

4x10^-7=[Sr

^{2+}][SO

_{4}

^{2-}]

Don't know where to go from here. Help is appreciated.