How do you determine volume from Ksp?

Question

Calculate how many milligrams of Ag2CrO4 will dissolve in 10.0 mL of H2O. Expermental Ksp value of Ag2CrO4=1.5x10^-12

err i meant mass not volume

Answer 1

First let's find the molar solubility (mole/L) of Ag2CrO4
If it is s, then

.. .. .. .. Ag2CrO4 <=> 2Ag(+) + CrO4(-2)
Dissolve .. s
Produce .. .. .. .. .. .. .. .. 2s .. .. .. ..s

Ksp= [Ag(+)]^2[CrO4(-2)] =(2s)^2s =4s^3 =1.5*10^-12 =>
s=7.21 *10^-5 mole/L

So in 10.0 mL you have
mole=M*V =7.21* 10^-5 * 0.01 =7.21*10^-7

MW Ag2CrO4 = 2 *107.87 + 52.00 + 4 * 16.00. = 331.71 g/mole

mole=mass/MW=> mass= mole*MW= 7.21*10^-7 *331.71= 2.39*10^-4 g =0.239 mg