1. Warmup 2/23/16 What is an oxidizer again? Oxidizers are usually very reactive. Why do you think this is? Objective Tonight’s Homework To learn how to identify redox reactions Finish Worksheet

2. Notes on Identifying Redox Reactions With the last lesson or two, we’re more equipped to identify redox reactions. Let’s review the rules we’ve said and do a bit of practice as a class.

3. Notes on Identifying Redox Reactions With the last lesson or two, we’re more equipped to identify redox reactions. Let’s review the rules we’ve said and do a bit of practice as a class. 1) An oxidizing agent: This is the substance in the reaction that will gain electrons. 2) A reducing agent: This is the substance in the reaction that will lose electrons. These are always reactants, not products. We can tell if something has lost or gained electrons based on oxidation number before and after the reaction.

4. Notes on Identifying Redox Reactions Example: Determine whether the reaction below is redox or not. If it is redox, identify the oxidizing and reducing agents. C H 4(g) + 2O 2(g)  C O 2(g) + 2H 2 O (g)

5. Notes on Identifying Redox Reactions Example: Determine whether the reaction below is redox or not. If it is redox, identify the oxidizing and reducing agents. C H 4(g) + 2O 2(g)  C O 2(g) + 2H 2 O (g) Rule 4 for hydrogen, Rule 6 for carbon Rule 1 Rule 3 for oxygen, Rule 6 for carbon Rule 4 for hydrogen -4 +10 +4 -2 +1 -2

6. Notes on Identifying Redox Reactions C H 4(g) + 2O 2(g)  C O 2(g) + 2H 2 O (g) Ok. So is this redox? Let’s look at carbon. On the left side, C has an oxidation of -4. On the right side, C has an oxidation of +4. This is redox because something changed. - CH 4 is the reducing agent. It lost electrons. - O 2 is the oxidizing agent. It gained electrons. -4 +10 +4 -2 +1 -2

7. Notes on Identifying Redox Reactions A few last things to note: 1) We can have one chemical be both the oxidizing agent AND the reducing agent. We see this sort of thing in a synthesis reaction. 2) We can also gain or lose partial charges. Technically, it just means electrons are being split unevenly between atoms, but the math will come out to show fractions of electrons. It’s ok. 3) If the number of atoms of a redox element changes from reactant to product, the number of electrons needs to be multiplied or divided to make sure we get the same overall charge.

8. Practicing Identifying Redox Reactions Let’s practice redox reactions. For each of the reactions on the worksheet, do the following: - Identify whether or not the reaction is redox - List the oxidation number for each element - Identify the oxidation and reduction agents Mr. C. will go over a few of these, even if we need to spill into tomorrow a bit.

9. Practicing Identifying Redox Reactions 1) 2Na + FeCl 2  2NaCl + Fe 2) 2C 2 H 2 + 5O 2  4CO 2 + 2H 2 O 3) 2PbS + 3O 2  2SO 2 + 2PbO 4) 2H 2 + O 2  2H 2 O 5) Cu + HNO 3  CuNO 3 + H 2 6) AgNO 3 + Cu  CuNO 3 + Ag

10. Exit Question What is the oxidizing agent? a) The substance that will lose electrons b) The substance that will gain electrons c) The substance that has lost electrons d) The substance that has gained electrons e) It depends on the reaction f) None of the above