00:01
So to calculate the molar mass of potassium, you need to consider the weighted average of the molar masses of its isotopes, taking into account their respective abundances.
00:18
So we would have potassium 39, and we would also have potassium 40, which we want, and potassium 41.
00:32
So in this case, the molar mass would equal the fractional abundance of isotope 1, 0 .9333, times this potassium 39, that's 38 .9637 grams per mole, plus relative abundance of 0 .067, this is potassium 41, which is 40 .9618 grams per mole.
01:23
And so when we add these together, it comes out to be 39 .0412 grams per mole.
01:40
So the molar mass of potassium is approximately, of potassium 40, is 39 .0412 grams per mole...