00:02
So they want the number of atoms in 11.5 grams of sodium.
00:07
To solve this problem, we need to know the atomic mass of sodium, and we looked this up in the periodic table.
00:13
The atomic mass of sodium is 22.99 grams.
00:16
That means the 22.99 grams of sodium contained one bowl of sodium atoms.
00:23
We know that one mole is 6.22 times 10 to the 23rd adams.
00:28
So in other words, they're 6.22 times 10 to the 23rd adams in 22.99 grams of sodium.
00:36
The problem asked for the number of atoms in 11.5 grams.
00:40
To find this, we need to know the proportion of grams that they ask for out of the atomic mass.
00:45
So what is the proportion of, ah, 11.5 grams out of the atomic mass 22 point sign? nine grams? and it turns out that this proportion is 0.5 00 too.
01:09
The same proportion of the grams of sodium that they give us out of the atomic mass will be applied to the number of atoms in the atomic mass.
01:22
So we know there's this number of adam 6.22 times 10 to the 23rd adams in 22.99 grams.
01:32
So we need to find what is 0.502 or the proportion that they're asking for, which is 11.5 out of 22.9.
01:41
That same proportion will be applied to the number of atoms, and that's how we find the number of atoms in 11.5 grams...