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AP® Chemistry: Rearrangement and Reorganization of Atoms Drill 1, Problem 1. Which of the following sets of coefficients correctly balances the below equation in the lowest whole number ratio?
Transcript
- 00:03
Here's your shmoop du jour, brought to you by Hot Tea.
- 00:06
If you spill it in your lap, it will burn for an Oolong time.
- 00:20
Damon decides to make a cup of hot tea by heating water with a gas stove.
- 00:26
The gas stove works through a combustion reaction involving methane gas, or CH4, and oxygen gas.
- 00:35
Which of the following sets of coefficients correctly balances the below equation in the
Full Transcript
- 00:40
lowest whole number ratio?
- 00:43
And here are your potential answers...
- 00:50
So this question is asking us to find the lowest whole number ratio to balance the equation.
- 00:57
If we take a quick look at the answers first, we know C can't be the right answer because
- 01:01
2, 4, 2, and 4 can be reduced to 1, 2, 1, and 2 by dividing all the numbers by 2.
- 01:07
So we can immediately eliminate C.
- 01:13
Now, let's figure out what will make this equation work. Other than, you know... offering
- 01:17
it a possible raise.
- 01:20
Well, in chemistry, according to the law of conservation of mass, there needs to be the
- 01:25
same number of atoms of each element on both sides of the equation.
- 01:29
Which means we can treat the arrow like an equals sign.
- 01:32
For this equation, we know there needs to be the same number of Carbon, Oxygen, and
- 01:36
Hydrogen atoms on the right side of the arrow as there are on the left.
- 01:41
To do this, we can place coefficients in front of the formulas to try to get equal numbers.
- 01:47
Let's try A. If we had 1, 1, 1, and 1...we'd have 1 Carbon on both sides, 4 hydrogens on
- 01:55
the left and 2 on the right...ok, we can stop there. That doesn't work.
- 02:01
B... 1, 2, 1, and 2. 1 Carbon on both sides, 4 hydrogens on the left and 2 times 2 for
- 02:10
4 hydrogens on the right.
- 02:13
2 times 2 is 4 for 4 oxygens on the left...and 2 plus 2 for 4 oxygens on the right.
- 02:21
The coefficients in answer B give us the same number of atoms on the left and right... which
- 02:25
is going to save us a bit of busy work.
- 02:27
Looks like B's our answer.
- 02:29
Now for Damon's next big task: getting the honey for his tea directly from the source...
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