00:02
All right, so here we have eight elements and we are tasked to find the mass percent of the first element in each compound.
00:15
All right, so let's recall the mass percent formula.
00:25
It's simply the mass of the element divided by the mass of one wall of the whole compound, right? okay, and the calculation for mass, if you remember, is moles multiplied by molar mass, right? so here, we don't have any information other than the chemical formula.
01:07
That's all we need, because we already know that there's one mole of compound, and we know the molar mass of each element by using our periodic table.
01:16
So let's first start off with iron two sulfate.
01:22
Let's first start off by listing out each element and their masses.
01:34
Okay, so if we have one mole of iron two sulfate, that means we have one mole of iron, one mole of sulfur, and four moles of oxygen.
01:46
Then we'll just multiply moles by the molar mass of each element.
01:52
So iron's molar mass is 55 .845 grams per mole, sulfur is 32 grams per mole, and oxygen is 16 grams per mole, all approximately.
02:13
Okay, then we sum up all of these masses to get the mass total.
02:25
All right.
02:28
Now to find mass percent of iron, we'll simply take its mass, its individual mass, 55, and then divide it by the total mass, 151 .9.
02:53
And then we get the mass percent to be 36 .76%.
03:07
Okay, so this is the method we'll use to do the rest.
03:14
Next up, we have silver oxide.
03:20
So first step, listing out each element.
03:24
Second step, getting down the mass of each element.
03:30
So we take moles and then multiply it by the molar mass.
03:37
So this is the molar mass for silver 107 .8.
03:46
And low mass for oxygen is just the 16 grams per mole.
03:52
Mm -hmm.
03:58
And if we sum that up, you get to 31.
04:04
Approximately, this guy's mass percent silver is then this mass, and we even circle it, this mass divided by the total mass.
04:27
Which then gives us 93%, which is quite high.
04:36
Okay.
04:38
Next up, we have strontium chloride.
04:44
Strontium is a group two metal, if you were wondering.
04:49
Okay, so we list out each metal, or each atom, sorry, and do the mass calculation.
04:59
One mole for strontium, two moles, for chlorine present in one mole of.
05:06
Strontium chloride the compound.
05:09
Okay, so then we'll just multiply by molar mass.
05:24
Mm -hmm.
05:26
Then once we sum this up, this is what we get.
05:35
Let me try and make that a bit more clear.
05:42
Mm -hmm.
05:44
And the strontimes mass percent is just this mass of the element over mass total, which will give us 55%...