00:01
So let's write some chemical equations from names to formulas.
00:09
And first, if we were to look at copper and have copper by itself, that's just cu.
00:18
In the solid state, we would put a parentheses in an x, s next to it.
00:25
And we're going to react that with solid sulfur s.
00:33
Sulfur and we're going to form copper 2 sulfide now copper 2 means that the charge of the copper is plus 2 the charge of the sulfide is minus 2 so 2 minus 2 is 0 we don't need any more coppers or sulfides in the formula of copper 2 sulfide c u2 s then is its formula and it is a solid so we'll put an s next to that and you can see this is balanced.
01:06
There's one copper on both sides of the equation.
01:09
There is one sulfur on both sides of the equation.
01:13
Now when we take solid iron three oxide, okay iron the roman numeral three in the word means the charge is plus three.
01:24
Oxide is negative two.
01:27
So to get these to balance out, we're going to have to find the least common multiple.
01:32
At least common multiple between two and three is six.
01:36
So to get six, i need two plus threes, and i need three minus twos.
01:43
So here i would have plus six, i have minus six, that's going to be neutral.
01:47
So my formula is really fe2, because i have two irons, o3, because i have three oxygens.
01:57
And i need each of those to balance the charges out to get no charge.
02:03
Now that iron three oxide reacts with hydrogen gas.
02:08
Hydrogen gas is h2, not h.
02:14
There are seven elements that form diatomic elements here.
02:20
Hydrogen is one of them.
02:22
And that's going to form solid iron.
02:26
Iron is just f .e.
02:29
Solid is s.
02:29
And liquid water.
02:31
So water we know is h2o and an l.
02:34
But this one we're going to have to balance.
02:38
And so to try to balance this one out, let's take a look at what we've got.
02:43
We have three oxygens, and we have one oxygen over here.
02:50
So if i put a three in front of the water, that'll give us three oxygens.
02:53
That balances out oxygen.
02:56
We now have three times two or six hydrogens on the right.
02:59
We need six on the left.
03:01
So we're going to need a three, three times two is six.
03:03
Now the hydrogens are balanced.
03:06
Iron, there's two on the left, there's only one on the right.
03:09
So if i put a two in front of iron, we balance out the iron.
03:17
In the next one, we have sulfur dioxide.
03:21
Die is two.
03:24
So dioxide means it's a molecular compound.
03:26
It's only non -metals.
03:28
We don't have to worry about charge.
03:30
Die tells us how many there are.
03:32
Two oxygens.
03:33
That is a gas, so we'll put a g.
03:38
Reacts with oxygen gas.
03:40
Oxygen gas is also a diatomic element.
03:43
It's always found in twos...