Balancing Equations  [ENDORSED]

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duenezjuleny1D
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Balancing Equations

Postby duenezjuleny1D » Wed Jun 26, 2019 11:04 am

When balancing an equation in lecture prof Lavelle multiplied the entire equation by 2 in order to get the lowest whole number. Will points be deducted on the test if we don’t do so ?

Sisi Li 1F
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Joined: Mon Mar 11, 2019 12:15 am

Re: Balancing Equations

Postby Sisi Li 1F » Wed Jun 26, 2019 3:47 pm

In lecture, Dr. Lavelle said that all stoichiometric coefficients must be the lowest whole number, so I imagine you would be docked points for leaving any coefficients in fractions.

Blanca Cervantes
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Re: Balancing Equations  [ENDORSED]

Postby Blanca Cervantes » Wed Jun 26, 2019 4:00 pm

You most likely would be deducted points since stoichiometric coefficients must be the lowest whole number

Daniel Kim 1D
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Re: Balancing Equations

Postby Daniel Kim 1D » Wed Jun 26, 2019 7:26 pm

I remember him saying that the ratios still make sense despite it not being a whole number. However for the sake of nature, I suppose, it is important to keep it at the lowest whole number to get your empirical/ molecular formula to get points on it on an exam.

David Zhang 1B
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Re: Balancing Equations

Postby David Zhang 1B » Wed Jun 26, 2019 7:52 pm

I would keep everything at whole numbers just to be safe. I haven't seen any chemical equations that have decimals or fractions as the stoichiometric coefficient.

gabbymaraziti
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Re: Balancing Equations

Postby gabbymaraziti » Sun Sep 29, 2019 4:22 pm

How are we supposed to know what number to multiply by in order to attain whole integers? Knowing if we need to multiply by 2 or 3 to reach a whole number is easy, but what about when the solution is more complicated?

alicechien_1I
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Re: Balancing Equations

Postby alicechien_1I » Sun Sep 29, 2019 4:34 pm

An easy way for me to determine what number to multiple a decimal by to get a whole number is to divide 1 by the decimal.

For example:
If there are 2.5 mols of C, do 1/0.5 = 2. You should multiply the 2.5 mols by 2 to get a whole number (5).
If it's a more difficult value, maybe like 2.125 mols of C, do 1/0.125 = 8. You would then multiply the 2.125 mole by 8 to get a whole number (17).

Anne Tsai 1F
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Re: Balancing Equations

Postby Anne Tsai 1F » Mon Sep 30, 2019 4:56 pm

When you need to use a stoichiometric coefficient that is not a whole number, you can write it as an improper fraction (such as 5/4). Then you will know to multiply the whole equation by the denominator (in this case 4) to get the lowest whole number.

Brian_Ho_1F
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Re: Balancing Equations

Postby Brian_Ho_1F » Mon Sep 30, 2019 6:21 pm

Conventionally the stoichiometric coefficients are whole numbers as it makes stoichiometric calculations more straightforward. Having whole numbers will make it easier to find out how many moles of Product A can be theoretically produced with x amount of moles of reactant B. It would be strange to say "if we have 6.5 moles of butane, we can produce 13.25 moles of H20" (arbitrary values) rather than "2 moles of butane can produce 8 moles of water given sufficient oxygen molecules" (again, arbitrary values). As the others have stated, I would most definitely make sure that the coefficients are whole numbers as it is the convention in every chemistry textbook that I have seen.

Sean Cheah 3B
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Re: Balancing Equations

Postby Sean Cheah 3B » Mon Sep 30, 2019 7:48 pm

alicechien_1I wrote:An easy way for me to determine what number to multiple a decimal by to get a whole number is to divide 1 by the decimal.

For example:
If there are 2.5 mols of C, do 1/0.5 = 2. You should multiply the 2.5 mols by 2 to get a whole number (5).
If it's a more difficult value, maybe like 2.125 mols of C, do 1/0.125 = 8. You would then multiply the 2.125 mole by 8 to get a whole number (17).


Huh, this is actually awesome. In the past, I've always used my intuition to make educated guesses about the correct factor, but this completely takes the uncertainty out of the equation. Can't believe I didn't think to try this myself and thank you so much for your post!

Michelle Xie 3A
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Joined: Sat Aug 17, 2019 12:18 am

Re: Balancing Equations

Postby Michelle Xie 3A » Tue Oct 01, 2019 4:34 pm

You would probably lose points. Also even though the equation is balanced without whole numbers, it doesn't make sense for there to be half of a molecule. It would not only make more sense but also make solving problems later on easier with whole number coefficients.

kim 4G
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Joined: Thu Jul 25, 2019 12:17 am

Re: Balancing Equations

Postby kim 4G » Tue Oct 01, 2019 4:42 pm

alicechien_1I wrote:An easy way for me to determine what number to multiple a decimal by to get a whole number is to divide 1 by the decimal.

For example:
If there are 2.5 mols of C, do 1/0.5 = 2. You should multiply the 2.5 mols by 2 to get a whole number (5).
If it's a more difficult value, maybe like 2.125 mols of C, do 1/0.125 = 8. You would then multiply the 2.125 mole by 8 to get a whole number (17).


This is a really interesting way of figuring out how to find whole number coefficients. Although, based on the example in class Lavelle used fractions, decimals for balancing chemical equations makes logical sense as well. Also, don't forget to find the simplest ratio of all the whole number coefficients at the end of balancing each chemical equation.

AChoudhry_1L
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Re: Balancing Equations

Postby AChoudhry_1L » Tue Oct 01, 2019 9:51 pm

alicechien_1I wrote:An easy way for me to determine what number to multiple a decimal by to get a whole number is to divide 1 by the decimal.

For example:
If there are 2.5 mols of C, do 1/0.5 = 2. You should multiply the 2.5 mols by 2 to get a whole number (5).
If it's a more difficult value, maybe like 2.125 mols of C, do 1/0.125 = 8. You would then multiply the 2.125 mole by 8 to get a whole number (17).


Thank you for this! I usually just try to make an educated guess, but this is a better approach and I will definitely be using it. Also, as a follow up question to the original question, do the coefficient have to be the lowest possible or is it okay to have bigger numbers as long as the ratios are the same?

AKatukota
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Joined: Thu Jul 25, 2019 12:18 am

Re: Balancing Equations

Postby AKatukota » Tue Oct 01, 2019 10:12 pm

All stoichiometric coefficients must be the lowest whole number, and multiplying by 2 would give the lowest whole number coefficients for that equation!

RKopeikin_3L
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Re: Balancing Equations

Postby RKopeikin_3L » Tue Oct 01, 2019 10:14 pm

I'm pretty sure most of the time when you balance chemical equations, you will not need to use fractions as stoichiometric coefficients. So I'd say for the most part don't worry about it, just make sure the coefficients are ALWAYS whole numbers. You may not run into many problems with fraction coefficients though.

105311039
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Joined: Fri Aug 02, 2019 12:16 am

Postby 105311039 » Tue Oct 01, 2019 10:21 pm

Yes! All coefficients should be put to the lowest whole number! I am not exactly sure if you will be deducted though.

Ying Yan 4H
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Re: Balancing Equations

Postby Ying Yan 4H » Tue Oct 01, 2019 10:32 pm

I think I can confidently say yes, since stoichiometric coefficients must be whole numbers.

605068586
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Joined: Fri Aug 09, 2019 12:17 am

Re: Balancing Equations

Postby 605068586 » Tue Oct 01, 2019 10:40 pm

If leaving the coefficients in fractions when solving for them is helpful, then do that first. After you balance the equation, you can just multiply all the coefficients by the common denominator for the fractional stoichiometric coefficients.

605068586
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Joined: Fri Aug 09, 2019 12:17 am

Re: Balancing Equations

Postby 605068586 » Tue Oct 01, 2019 10:41 pm

If leaving the coefficients in fractions when solving for them is helpful, then do that first. After you balance the equation, you can just multiply all the coefficients by the common denominator for the fractional stoichiometric coefficients.

Maika Ngoie 3E
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Joined: Fri Aug 02, 2019 12:16 am

Re: Balancing Equations

Postby Maika Ngoie 3E » Wed Oct 02, 2019 10:47 am

gabbymaraziti wrote:How are we supposed to know what number to multiply by in order to attain whole integers? Knowing if we need to multiply by 2 or 3 to reach a whole number is easy, but what about when the solution is more complicated?


normally, the numbers should be pretty easy fractions, but if they turn out a little messy I would probably check the previous compounds that I have balanced, as an error in those balances may affect the math later on

Debora Fernandez Clemente_ 4H
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Re: Balancing Equations

Postby Debora Fernandez Clemente_ 4H » Wed Oct 02, 2019 3:14 pm

When balancing equations how do you determine what to balance first?

905289082
Posts: 51
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Re: Balancing Equations

Postby 905289082 » Wed Oct 02, 2019 3:18 pm

duenezjuleny1D wrote:When balancing an equation in lecture prof Lavelle multiplied the entire equation by 2 in order to get the lowest whole number. Will points be deducted on the test if we don’t do so ?


I would assume you'd receive a lower grade if you didn't do something similar, because if you recall, in the example, he did that so that the subscript in the equation was a whole number. You can't submit a final equation with a fraction of an atom in it, so you should always multiply the whole thing by whatever number it requires to make it a whole number before submitting a final answer.

Cynthia Rodas 4H
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Joined: Wed Sep 18, 2019 12:21 am

Re: Balancing Equations

Postby Cynthia Rodas 4H » Wed Oct 02, 2019 3:28 pm

Debora Fernandez Clemente_ 4H wrote:When balancing equations how do you determine what to balance first?


My TA recommended that we start with balancing the elements that appear the least in a chemical equation.
For example:
You would start with either the Carbons or Hydrogens since they each only appear twice throughout the entire chemical equation whereas the Oxygen appears three times.

Charlotte Coplon 1K
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Joined: Thu Jul 11, 2019 12:15 am

Re: Balancing Equations

Postby Charlotte Coplon 1K » Wed Oct 02, 2019 3:32 pm

The stoichiometric coefficients in chemical equations must always be the lowest integer (whole number). In the example he gave in class, Prof. Lavelle multiplied the equation by two to get rid of the fraction. What he was left with were the lowest whole numbers possible. I don't think you are supposed to leave fractions in a chemical equation when balancing it. Always find the lowest possible whole numbers (even if it means having to multiple to not have fractions).

erica thompson 4I
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Re: Balancing Equations

Postby erica thompson 4I » Wed Oct 02, 2019 11:58 pm

That was definitely a technique he used for that specific problem! Working with stoichiometry problems will never have the same set of moves for each problem. In this case, we had a coefficient with a denominator of 2, so we had to multiply the entire problem by 2 in order to get rid of the fraction. If there was a coefficient of lets say 1/3, you might consider multiplying the whole equation by 3 (but again, each problem has its own way of getting solved, or potentially multiple strategies).

Lindsey Chheng 1H
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Re: Balancing Equations

Postby Lindsey Chheng 1H » Thu Oct 03, 2019 12:11 am

duenezjuleny1D wrote:When balancing an equation in lecture prof Lavelle multiplied the entire equation by 2 in order to get the lowest whole number. Will points be deducted on the test if we don’t do so ?


The reason why we want all coefficients to be whole numbers is because we are trying to find the mol to mol ratio between reactants and products in a chemical reaction, and it's easier to work with whole numbers.


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