00:01
The equilibrium equation for iron two hydroxide is iron two hydroxide solid, goes to iron two plus and two hydroxides.
00:11
So ksp is going to be equal to the iron concentration multiplied by the hydroxide concentration squared.
00:17
Molar solubility is provided at 6 .0 times 10 of the negative 1 milligrams per liter, or 0 .60 milligrams per liter.
00:28
We can convert the milligrams into grams by dividing by a thousand, and then convert the grams of iron two hydroxide into moles by dividing by its molar mass.
00:39
So now we know the moles of the solid that dissolve per liter, which is the definition of molar solubility, 6 .68 times 10 to negative 6 moles per liter.
00:50
Ksp then is going to be equal to.
00:52
If the only source of iron 2 plus comes from iron 2 hydroxide, we get one mole of it for every 1 .5.
00:58
Molar the compound so the iron concentration is equal to molar solubility we get twice as much hydroxide so the hydroxide concentration will be two times molar solubility so then we plug in 6 .68 times 10 to the negative 2 wherever we have the s and we calculate our ksp value as 1 .19 times 10 to the negative 15 now knowing the ksp value and knowing that we want to target iron concentration of 1 .0 micrograms per liter, we need to convert the micrograms per liter into a molarity.
01:37
To do that, we'll divide by, they're just referring to the micrograms of iron 2 plus, so we'll divide by the molar mass of just iron 2 plus...