00:01
Out of three different salts.
00:07
So let's start from the first one, na3, as, arsenic, and o4.
00:19
So for each one of it, you will have to calculate the molecular weight, and then you know the percentage of arsenic in each compound.
00:30
So first of all, let's calculate this one.
00:34
Molecular weight is 3 of the sodium and arsenic itself is 40 74 .9 there's a 1 and oxygen is 16 this is the number of molecule in a number of this element in this molecule we add them up together that is 2207 .9 gram per mole now we want to calculate the percentage of arsenic, we just take the molecular weight of the arsenic, which is 74 .9, divided by the molecular weight of the entire molecule, multiplied by 100%.
01:37
That is around 36%.
01:43
Use the same method, you will calculate the second one.
01:46
Second one is as2 and o3.
01:55
So use the same method.
01:57
We calculate the molecular weight of this molecule.
02:00
So the molecular weight is 2 times arsenic 74 .9 plus oxygen 16, 16 and you have 3 of it times let's write down 74 .9 times 2 plus 16 times 3, number of those elements.
02:31
74 .9 times 2 is 149 .8 and plus 48, that is 197 .8 gram per mole.
02:49
So basically i use the molecular weight of each element and multiply by the number of these elements in this chemical compound and calculate the molecular weight of entire compound...