00:01
To determine the molar solubility of barium sulfate, we recognize that barium sulfate as a solid is involved in an equilibrium when in water, producing barium ion and sulfate ion.
00:16
Ksp for this equilibrium is equal to the barium concentration at equilibrium multiplied by the sulfate concentration.
00:26
They didn't give us this ksp value, so we'll have to look it up in the table i have.
00:32
Ksp for barium sulfate is 1 .1 times 10 to the negative 10.
00:41
So if we already know the sulfate concentration, they tell us that the sulfate concentration comes from sodium sulfate at 0 .018 molar.
00:58
Then when one mole of this dissolves in a liter of solution, we'll get one mole of barium ion in a liter of solution.
01:06
So we can state that the barium ion concentration is equal to the moles of the solid that dissolved in a liter or molar solubility.
01:15
So now we plug these two back into the ksp expression and we solve for molar solubility.
01:21
Molar solubility, which is the barium concentration, will be equal to ksp 1 .1 times 10 to the negative 10 divided by the sulfate concentration, which they gave us as 0 .018 molar...