00:01
To determine how many grams of pbf will dissolve in 700 milliliters of a solution that already contains fluoride, we need to write the dissolution reaction, pbf2 as a solid, will dissociate into pb2 plus and two fluorides.
00:22
So the ksp expression will be equal to the pb 2 plus concentration, multiplied by the 5b2 plus concentration, fluoride concentration squared, and they tell us that this value is 2 .69 times 10 to the negative 8.
00:44
So what we can do is first calculate what's called molar solubility, which tells us the moles of the solid that dissolves in a liter of solution.
00:55
When one mole of this solid dissolves in a liter of solution, we get one mole of pb2 plus dissolved in a liter of solution.
01:04
So the concentration of pb2 plus will represent the molar solubility or the moles of solid that dissolved in a liter of solution.
01:16
I'll represent molar solubility as s.
01:19
The fluoride concentration, however, is set by the additional sodium fluoride in the solution.
01:26
That's at so going back to our ksp expression, we can solve for molar solubility.
01:37
Pb is equal to molar solubility...