wah3da
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I have an exam this Friday and I have no idea how to balance chemical equations. I've watched so many videos on it and even in class, my teacher only went over it once. Can someone help me out on balancing chemical equations? THNX
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helpiamlost
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The number of each atom needs to be the same on both sides of the equation. The ONLY thing you can do is change the coefficients of each species.

That's really all there is to it.

As an example:
C4H10 + O2 -> CO2 + H2O

As you can see, there is 4 C on the left but only 1 on the right. 10 H on the left but only 2 on the right. 2 O on the left but 3 on the right. Not balanced.

First balance C
C4H10 + O2 -> 4 CO2 + H2O

Then H
C4H10 + O2 -> 4 CO2 + 5 H2O

Finally need to do O and it gets a bit tricky. We have 8 O in the 4 CO2 and 5 O in the 5 H2O. 8 + 5 = 13 so we need to get 13 O atoms on the left. Since it is O2 if we do 13/2 (or 6.5) O2 then it will balance.

C4H10 + 13/2 O2 -> 4 CO2 + 5 H2O

But we don't really like seeing that fraction, so instead if we multiply the entire equation by 2 it will get rid of it.

2 C4H10 + 13 O2 -> 8 CO2 + 10 H2O
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ChemistryWebsite
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I would only add that there is a golden rule, one I have come to realise isn't obvious to all students:

Before you balance the sides of the equation you must make sure each formula you are using is the correct formula. Don't try to manipulate formulae for convenience - the formula is the formula regardless of how easy it makes balancing the equation.
It sounds obvious, but I have come across so many students who try to change formulae to make the balancing easier.

You may also want to have a look at my post here


Good luck with your test.
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