Posted by Cori on .
I'm confused with this question as I don't understand how to write the reactions. Here is the question if you could please help me with this question or just even give me an example on how to do it. I would really appreciate it. Thank you.
Write the oxidation and reduction half reactions for the following full reaction.
AgBr + Na ==> Ag + NaBr
I just don't understand how to write the oxidation and reduction half reactions, I only know how to do full reactions.
First you separate the full reaction which you have written into the two half reactions. To do that, follow these steps.
1. Write the oxidation state of each element/ion above it. For example, above Ag in AgBr you place a +1. Br in AgBr is -1. Na is zero (all elements are zero. Ag on the right is zero, Na in NaBr is +2 and Br in NaBr is -1.
2. What changed?
a. Ag changed from +1 on the left to zero on the right. So the half reaction for that is Ag^+1 + e ==> Ag.
b. Na changed from zero on the left to +1 on the right. So the half reaction for that is Na ==> Na^+1 + e
c. note that Br didn't change. It was -1 on the left and it is -1 on the right.
d. Then label each half reaction as oxidation or reduction. To do that you simply remember the definitions.
Oxidation is the loss of electrons (have you heard the mnemonic---Leo the lion goes Grrrrr---Leo tells you. Loss Electrons Oxidation. Of course reduction is the opposite; i.e., gain of electrons is reduction.
The Ag half reaction is reduction (because it ADDED an electron). The Na half reaction is oxidation (because it LOST an electron.)
Here is a site to help you do oxidation states if you are unsure about them.
Chemistry typo correction -
Na in NaBr is +1 (not +2)
Thank you for your help, especially the Leo the lion, thank you, I couldn't say it enough. You have helped me so much. Thank you.