00:01
Okay, so we have five isotopes of nickel and we're given the masses which are listed here and the percent of each.
00:09
And we want to know what the average is.
00:13
Now remember the average when we're talking about these is not just take the numbers and divide by five because there's five isotopes.
00:20
It's a weighted average because we have more of nickel here with a mass of 57 .9353 than we do any of the others.
00:30
So it's a weighted average, like a test grade versus a homework grade.
00:36
So the average is equal to the sum of the masses times their percent abundance.
00:46
And then when we do that, we're going to divide by 100 because we have a total of 100%.
00:51
So we have five of them.
00:52
So we're going to sum up five of them.
00:54
So the average, we're going to take the mass, the first mass, 57 .9353.
01:04
And we're going to multiply by the percent 68 .08.
01:10
And then we're going to sum up.
01:12
So we're going to do that with the other four isotopes...