00:02
Hello everybody.
00:04
So this problem, let me read it out for you, it says you have a pure gold ring of mass 10 .8 grams.
00:13
Gold has an atomic mass of 197 grams per mole.
00:17
So let me write that stuff out.
00:19
So the mass of the actual thing is 10 .8 grams.
00:30
Now the atomic mass, which i'm going to label big m, of gold is 197 grams per mole.
00:41
Now what is a mole? you should know that.
00:45
But no.
00:47
A mole is a kind of unit that represents the number of atoms that can consist in a mole.
00:59
I don't know how to necessarily explain it, but i'll get back to.
01:03
It later on or maybe soon i'm not sure um so anyways we've got that and an atomic number of 79 so 79 means in gold there's 79 protons so e plus anyways and the questions are how many protons are in the ring and what is their total positive charge so first we want to determine how many the number of moles basically of gold are in this ring so we have the big m how many grams per mole and we have how many grams of the atoms the gold atoms or just not gold atoms but of the substance of the element itself anyways so we're going to label this n that is the number of moles.
02:13
Now the number of moles is going to be the mass of our element, the amount of mass that we have over the atomic mass of that same element.
02:27
That'll cross out the gs and bring moles as a unit to the forefront to the numerator.
02:34
So we're going to do that math real quick.
02:39
This is one of the steps in the longer run of the whole thing because once we know, we know know how many moles we can move on to determining how many atoms of gold are in the in the ring itself anyways let's do this math real quick do that math with your calculator and we get let me see let me pull it up 10 .8 over 197 .0 .0 0 .054.
03:36
548.
03:38
Now, we can keep it like this or we can just keep it as this fraction for now because we're going to be multiplying this n with something else.
03:47
So, for good purposes, we can just ignore this for right now.
03:53
Just ignore that calculation, keep it as a fraction for the moment because what we want to determine next is the number of atoms of gold number of boop number of gold all right so how do we do that how do we determine that we determine that by multiplying the number of moles that we've determined it to have times a constant called avogadro's number which is denoted n subscript capital a now avogadro's number is the amount of atoms of any substance per mole.
04:52
So let me just go like this real quick.
05:01
Let me see.
05:02
Let me write it like right there or something.
05:06
So na is alvagadjo's number.
05:11
And this number, you may have heard in chemistry class or maybe not at all depending on what you've been doing with your life.
05:21
I don't know.
05:23
But anyway, so avogadra's number is 6 .02 times 10 to the 22nd atoms per mole.
05:34
Now, this is just atoms of any substance.
05:38
It's just like a representation.
05:41
So, for example, it's saying like a mole is like a, we can think of a mole as, as like a measuring cup, like a measuring cup, like a measuring cup for one cup.
05:57
And your faucet is dripping how many is dripping into the cup right so avogadra's number tells you how many drips water droplets from the faucet would be required to fill up that one cup it's going to be the same no matter what because wherever you get a measuring cup it's always going to be for one cup right so in the same vein that's what what this number basically tells us.
06:33
No matter what type of atom you're referring to, this is how many atoms equal one mole of that same substance.
06:46
We're going to use this number and the number of moles to determine the number of gold atoms that we have.
06:56
Now, multiplying this fraction to this big old number here gives us 3 .3.
07:07
0 add that little 0 just for statistical analysis means and i say statistical analysis means just because this has three digits 108 and 197 so we're just going to keep this trend going 3 .303 digits even though the zero isn't necessarily needed we're going to keep it so that's how many atoms of gold we have cool now let's go back to the question it says how many protons are in the ring and what is their total positive charge so now that we know how many gold atoms there are and we know how many protons are in one gold atom okay 79 we can solve part a we can say since there is this many atoms and this many protons per atom, we can multiply this stuff together.
08:33
Do do do, do...