00:01
To calculate the percent composition of a compound, we need to know what is meant by percent composition.
00:10
Percent composition is specifically defined as the mass percent composition, not the atom percent composition.
00:22
So sometimes the student gets confused, looks at the chemical formula.
00:26
We see that there are five moles of carbon in a mole of the compound, and me.
00:35
There are a total of 10 moles of atoms, so they say it's 50 % carbon.
00:41
That would be an atom percent, but an atom percent is rarely calculated, if ever.
00:47
So when a question asks percent composition, it is referring to mass percent, and you need to calculate masses.
00:55
A mass percent is simply the mass that is an element divided by the total mass of the compound times 100.
01:02
To calculate these mass values, we need to make an assumption first.
01:08
The assumption that we make is we have one mole of compound.
01:14
If we have one mole of compound, then knowing the chemical formula, in this case for msg, we can use the subscripts to refer to the moles of each element in one mole of the compound.
01:29
So if i have one mole of msg, i have one mole sodium, 5 moles carbon, 8 moles hydrogen, 1 mole nitrogen, 4 moles oxygen...