At 25C only .0190 mol of the generic salt AB2 is soluble in 1.00L of water. What is the Ksp of the salt at 25C?

AB2A^2+ + 2B^-

I took the .0190 mol and doubled it and multiplied by .019 again and got 6.859×10^-6 and got it wrong what should I do?

AB2A^2+ + 2B^-

I took the .0190 mol and doubled it and multiplied by .019 again and got 6.859×10^-6 and got it wrong what should I do?

Please help Dr. Bob

1 Answers

Did you square the 0.019*2 for B^-?

……..AB2 ==> A^2+ + 2B^-

I……solid….0…….0

C…..-0.0190..0.019..0.019*2

E……solid…0.019..0.038

……..AB2 ==> A^2+ + 2B^-

I……solid….0…….0

C…..-0.0190..0.019..0.019*2

E……solid…0.019..0.038

Ksp = (A^2+)(B^-)^2

Ksp = (0.019)(0.038)^2

Ksp = 2.74E-5 for the answer. I do it slightly different because it’s faster on the calculator.

Ksp = (A^2+)(B^-)^2

Kso = (x)(2x)^2 = 4x^3

Ksp = 4*(0.019)^3 = 2.74E-5.

The usual student mistake is to double the 0.019 to find B^- but forget it is squared.

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