00:01
We are asked to consider the complete combustion of octane.
00:05
We are given atomic weights as whole numbers, and we're asked several questions.
00:11
Question number, letter a.
00:13
How many moles of oxygen are unknown is moles of oxygen to burn 3 .9 moles of octane.
00:28
Okay, 3 .9 moles of c8h18.
00:34
And we'll multiply that by 25 over 2.
00:39
That's from our balanced chemical equation.
00:45
Can we do that? 3 .9 times 25 divided by 2.
00:51
That'll be equal 48 .75.
00:56
And then to round this to two significant figures will be 49 moles of 02.
01:06
Next, letter b, grams of co2 from 8 .4.
01:16
5 moles of octane.
01:22
Also easy -peasy.
01:30
I have a 2 to 16 mole ratio for co2 to octane, and the molar mass is 44 .01 grams of co2 per mole of co2, 8 .5 times 16 times 44 .01 divided by 2.
01:56
And this will be, can that be right? 8 .5 times 16 is 100 times 44 would be 2 ,992.
02:14
And that will equal to two sig figs 3 .0 times 10 to the third grams.
02:29
Next, if 455 grams of 02 react with 1 .5 grams of 02, we act with 1 .4 .5 grams.
02:42
5 moles of octane.
02:49
How many moles of excess remain? okay, so let's go ahead and just figure this out.
03:06
I always just start with my first one.
03:08
This is 32 .00 grams of oxygen per mole of oxygen.
03:14
I would have a 25 to 2 mole ratio, and this will tell me how many moles of octane would be consumed...