Here's a refresher on the rules for Redox reactions (see number 7 on Getting Started worksheet).
1. Each atom in a pure element has an oxidation number of zero. Example: Mg(solid), O2(diatomic oxygen)
2. For ions consisting of a single atom, the oxidation number is equal to the charge on the ion. Example: Ca2+, Cl-
3. Fluorine is always -1 in compounds with other elements.
4. The oxidation number of H is +1 and of O is -2 in most compounds.
5. Cl, Br, and I are always -1 in compounds (except when combined with oxygen and fluorine.)
6. The algebraic sum of the oxidation numbers in a neutral compound must be zero; in a polyatomic ion, the sum must be equal to the ion charge. Example: NaCl (Na is +1, Cl is -1), OCl- (O is +2, so Cl is -3 to get overall charge of -1).
Group one metals are +1, group two metals are +2.
Transition metals can have different oxidation numbers, no rule of thumb. Example: Fe +2, Fe +3
There may be exceptions to some of these rules, but for our class, this is what you need to know. We will get back to Redox reactions when we cover Electrochemistry later this semester.
Here's a link for some more practice:
Oxidation Numbers
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2 comments:
This isn't regarding the Redox rxns but rather the previous lab. The "Reporting Criteria" (from the sheets we printed off the web) says we should be calculating the mean delivery volume, std dev, rel std dev, and pipet calibration factors. The last 2 are not in our spreadsheets. Should we just put them on the spreadsheet anyway? Also, are we just comparing the accuracy of the 1000 microliter pipets to what we found in lab? If we are also comparing the precision, can we use the std dev for that comparison? I didn't quite know where the post these questions, so I hope here is alright. Thanks.
Since they were not in the spreadsheet originally, you can leave out the pipet calibration factors. You can put %RSD in the column that says "% error."
The answer to the other two questions is yes.
I hope this clears up some of the confusion, I should be available on Thursdays from now on to answer any lab questions.
thanks!
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