00:01
In this question, which is question number 107 of chapter 1 in chorus chemistry, structure and properties, we've been told that a sample, which is an alloy, is composed of gold and palladium, and the total mass of this sample is 67 .2 grams.
00:23
And the number of atoms in this sample is 2 .49, 10 to the power 23.
00:28
And we've been asked to find the percent composition by mass of, i guess, either one of these components, right? so the first thing you want to do is to determine what the molar mass of these two elements are.
00:49
So a quick look at the periodic table suggests that the molar mass of gold is 197.
00:56
It's actually 196 .97, but i've approximated here.
01:02
As 197 and for palladium is around 106.
01:10
So assuming we call, or we denote x to be the moles of gold and y to be the moles of palladium, we can actually write an expression by combining the moles and the molar mass to give the mass.
01:49
Mass right because the mole is equal to the mass over the molar mass so the mass is essentially the moles times the molar mass right so essentially if we multiply this moles by the molar mass which is which has units grams per mole we would get the mass so the first thing we should be writing this for this question is that x right which x is the moles of gold times the molar mass which is 196 .97.
02:39
I'm going to ignore the units here for the final answer and we add that to the mass of palladium and the mass of the palladium is going to be the moles of palladium times the molar mass.
03:02
So you have the moles times mulla mass which is 106 .42.
03:17
So i'm using the exact molar mass.
03:21
That's been recorded in the periodic table.
03:24
Like i said, i'm going to ignore the units here until the final answer.
03:31
So this is the total mass and that has been given, this would give us a total mass and that is 67 .2.
03:42
Right? so this is one component of the question...