Author Topic: Balancing Chemical Equations  (Read 210 times)

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Offline Adrian the Goat

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Balancing Chemical Equations
« on: February 27, 2017, 09:24:45 pm »
The Law of Conservation of Mass states that mass can never be created or destroyed. Although this law is broken in quantum physics by the Casimir effect, it fully applies to physical sciences such as chemistry. I understand the basics of balancing chemical equations. There must be the same number of atoms on each side of the chemical equation. I can even balance simple chemical quations. Here's an example of a double replacement of silver nitrate and zinc chloride:

2AgNO3 + ZnCl2 = 2AgCl + Zn(NO3)2

The equation above is rather simple. Before, there was only one nitrate, but there was two after the reaction. To satisfy the Law of Conservation of Mass. To correct this, two was added to the silver nitrate. Another silver atom was required as well as another silver, thus a two was also placed before silver chloride.

These equations make perfect sense to me but then there are equations such as this one:

CoBr3 + CaSO4 = CaBr2 + Co2(SO4)3.

This equation shouldn't be that difficult to solve from other people's experiences, but these are incredibly difficult for me to solve. I feel overwhelmed whenver I see all the subscripts together. There's no way to balance the equation without altering the entire equation. I can't even solve these but I have a test over them tomorrow. Do any of you have a technique for balancing complicated chemical equations or any sort of method to make them less stressful?

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Offline Alastair

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Re: Balancing Chemical Equations
« Reply #1 on: February 27, 2017, 09:40:27 pm »
Ah, something I know about! I quite enjoy chemistry, so I'd be glad to help out!

I'd solve it like this:

2CoBr3 + 3CaSO4 --> 3CaBr2 + Co2(SO4)3

Co: 1 2                       Co: 2
Br: 3 6                       Br: 2 6
Ca: 1 3                       Ca: 1 3
S: 1 3                         S: 3
O: 4 12                         O: 12

And that should solve it. See what I'm doing there? I like to make a table of the elements in either side of the equation (make sure corresponding elements line up, even if they're in a different order on either side!), and write out how many of each element there are to start out with. Now you can see how the amounts of each element differ. Then you can begin to balance it. For example, I saw that there were 2 cobalt atoms on one side, and 1 on the other, so I added a '2' in front of CoBr3 on the left side, and that balanced the amount of cobalt atoms. Then I crossed out the '1' cobalt and the '3' bromide and adjusted the numbers appropriately. Just keep going through this process until all the numbers are balanced!

Hopefully this makes sense, please let me know if you need any more help and I'd be more than happy to provide it!
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Offline Adrian the Goat

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Re: Balancing Chemical Equations
« Reply #2 on: February 28, 2017, 04:05:59 pm »
Ah, something I know about! I quite enjoy chemistry, so I'd be glad to help out!

I'd solve it like this:

2CoBr3 + 3CaSO4 --> 3CaBr2 + Co2(SO4)3

Co: 1 2                       Co: 2
Br: 3 6                       Br: 2 6
Ca: 1 3                       Ca: 1 3
S: 1 3                         S: 3
O: 4 12                         O: 12

And that should solve it. See what I'm doing there? I like to make a table of the elements in either side of the equation (make sure corresponding elements line up, even if they're in a different order on either side!), and write out how many of each element there are to start out with. Now you can see how the amounts of each element differ. Then you can begin to balance it. For example, I saw that there were 2 cobalt atoms on one side, and 1 on the other, so I added a '2' in front of CoBr3 on the left side, and that balanced the amount of cobalt atoms. Then I crossed out the '1' cobalt and the '3' bromide and adjusted the numbers appropriately. Just keep going through this process until all the numbers are balanced!

Hopefully this makes sense, please let me know if you need any more help and I'd be more than happy to provide it!
I read this post and even shared your method with my chemistry teacher. She said that she'd show it to those who struggled with balancing the equations. During third period, I was surprised to know that the test was only five questions long. Along with its short length, the test didn't have any of the overly difficult chemical equations like I thought it would. I was thinking about your method of balancing the equations while taking the test and I can honestly say that it worked incredibly well. I was also thinking of the factors of the subscripts which I find to also help from time to time. I currently have no grade back from the test being as I took it today, but I'm very confident that I did well. I was so nervous beforehand, but you've helped me greatly. Thank you very much, Alastair!

Also, to those who may struggle with balancing chemical equations, I'd highly reccomend Alastair's method. Factoring compliments his method well too. The factors are rather simple considering that very few compounds exceed four as the subscript. The factors seem to work with the larger equations which are distributed throughout the equation. For example, four and two share several factors including eight and twelve. This is useful for determining the overall total of atoms on each side of the equation which must be the same on both sides to satisfy the Law of Conservation of Mass.
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