### calculating n

Posted:

**Tue Feb 20, 2018 11:47 pm**How do you calculate moles of electrons? Do you need to go through the whole balancing process to find that?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=141&t=28269

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Posted: **Tue Feb 20, 2018 11:47 pm**

How do you calculate moles of electrons? Do you need to go through the whole balancing process to find that?

Posted: **Wed Feb 21, 2018 1:28 am**

You have to look at how many electrons are transferred in the balanced half-reactions. In other words, find the number of electrons in each balanced half-reaction. If they match, that is n. If they don't match, take the lowest common multiple, and that is n.

Posted: **Wed Feb 21, 2018 2:21 pm**

You can look at the overall reaction, and split it into 2 half reactions. For example, if one of the half reactions for the total equation is Cr3+ + 1e- -----> Cr2+, then here one electron is being transferred. However, if there are 2Cr3+ and Cr2+, then you know there are 2 electrons transferred because for ever one mol of each of these ions, one electron is transferred.

Posted: **Thu Feb 22, 2018 12:05 am**

You look at the electrons transferred during the half reactions.

Posted: **Sun Feb 25, 2018 6:45 pm**

Yes, you need to work out both half reactions and balance them properly to get the same amount of electrons being gained and lost in both half reactions. The mutual number of electrons in both half reactions is the number for n.

Posted: **Sun Feb 25, 2018 9:27 pm**

Yes you would work out the half reactions then balance the reactions out. The e- that results from the balanced half reaction will be the moles of e- you use for the equations.

Posted: **Sun Feb 25, 2018 9:40 pm**

When we get the two half reactions and balance the charges by adding electrons, we have to make the electrons added to each half reaction equal by multiplying each reaction by a number that will do so. Once the number of electrons added to both half reactions is equal, the number of electrons added to the half reactions is the value of n. In other words, the number of electrons that end up cancelling out of both reactions is the value of n.

Posted: **Sun Feb 25, 2018 11:37 pm**

To calculate n you would need to find the number of electrons transferred in each half reaction. If they match up, that is your n value. If they don't the lowest multiple of the two is you n value.

Posted: **Mon Feb 26, 2018 11:42 am**

You can look at your balanced half reactions and it will show you how many moles of electrons are going to be exchanged during the reaction.

Posted: **Sun Mar 18, 2018 1:18 am**

You proceed through the redox reaction as normal and then count the number of electrons. Remember to multiply the half-reactions beforehand, so the moles of electrons are equal to each other. The number of electrons, then, is "n".