Say what?
Different than the oxidation number method.
"But, but, but.... how will I know which method to use?"
The question will ask you to use one method or the other method.
You will be told!
The method:
-if the reactionis acidic or neutral (neutral = no mention of either acidic or basic conditions)
divide the reaction into two half reactions (an oxidation half and a reduction half) - [at this stage it should be quite obvious about the halves]
Working with one half reaction at a time:
-balance species except for H and O
-balance O by adding H2O
-balance H by adding H+
-determine charge on reactant/product side of half reaction
-add electrons (e-) to balance charges
-at this point one reaction should have electrons on the reactant side (reduction half cell - gained electrons) and the other half reaction should have electrons on the product side (oxidation half cell - lost electrons)
-make electrons equal by multiplying entire half reactions by necessary coefficient
-add up the two halves, simplify (cancel) as needed
Check the finished reaction by ensuring that the charge is equal on both sides and that the atoms are balanced.
If the reaction is basic, add OH- to both sides equal to the number of H+ in the reaction
Simplify the water: OH- + H+ = H2O (cancel/reduce water that lies on both sides of the reaction)
Check the finished reaction
The above outlined procedure follows along with the Nelson text. There are variations of the procedure out there that also work. Worked out examples can also be found in the Nelson text.
Practice quiz/test type questions?
Try the following Waterloo links. There is a lesson presented and some practice questions that follow - with answers. Some of the questions are are at greater level of difficulty than expected for this course. But everyone likes a challenge, right?
Oxidation States: http://www.science.uwaterloo.ca/~cchieh/cact/c123/oxidstat.html
(Again some variations of the oxidation rules have been presented. The oxidation answers do not change.)
Half Reactions: http://www.science.uwaterloo.ca/~cchieh/cact/c123/halfreac.html
Balancing Half Reactions: http://www.science.uwaterloo.ca/~cchieh/cact/c123/balance.html
Not that you are expected to be doing a lot of Chem*Is*Trying over the Winter Break, but....
The final answers to all of the reactions (oxidations, oxidation under A/B conditions and half reaction balancing) have all been moodlized.
The the next lesson (Galvanic Cells) and unit review have also been moodlized. Please note, if you decide to work ahead on the Galvanci cell stuff - the Nelson text does something a wee bit different than the representation style than will be followed in the classroom lessons. The text opted for their own version of "Cell notation", it is not Standard Cell Notation as many others follow. The following link provides examples of the classroom lesson format: pages.towson.edu/ladon/electrochem.doc
EChem in the New Year
-Galvanic Cell
-Galavanic Cell lab/Corrosion Lab
-Corrosion and Corrosion Prevention
All of the organic reaction handouts have also been moodlized.
If someone gets really organized, exam review will also get moodlized.
The moodle may get a bit of revamp over the Winter Break. The ask a question forum may shift to the top of the page so that it becomes an ask a question about any unit. The forum for question question asking is checked on a regular basis. Take advantage of the opportunity. During the break, answers may not appear immediately, but they will still appear. [Unless technical gremlins get in the way.]
May each and everyone of us enjoy our respective Winter Break.
