Redox Reactions Categorizing Chemical Reactions All chemical reactions

Redox Reactions

Categorizing Chemical Reactions �All chemical reactions involve something moving, so we can categorize the types of reactions we just learned to help us predict the products in a reaction! Moving electrons = synthesis, decomposition, and single displacement Moving ions = double displacement Moving protons = acid/base reaction (we’ll get into this in a later unit) Combustion is actually a combination of these

�This first example should make sense because this is simply the creation of an ionic bond, from the transfer of electrons: Mg + Br 2 Mg. Br 2

�The second example is just the opposite, breaking down an ionic bond. 2 Na. Cl 2 Na + Cl 2

�Ex: Zn + Cu. SO 4 Cu + Zn. SO 4 �Remember Cu. SO 4 is an ionic compound, so it really is made of Cu+2 and SO 4 -2, while Zn is starting off neutral in the reactants �During this reaction, Zn transfers its electrons to Cu+2, turning the metals into a Zn+2 ion and a neutral Cu atom. �Now that Zn+2 has a charge, it will form the ionic compound with SO 4 -2 because of opposite charges.

�In this case, did the sulfate ion see an change of electrons? �No, so these electrons were not involved in the reaction and weren’t shown, but remember sulfate has 2 extra electrons to make its structure stable (the -2 charge)

Reduction and Oxidation �In these reactions, one atom or element is reduced and the other is oxidized So you’ll often hear these called Redox reactions �A substance that is reduced has gained electrons and therefore reduced its charge �A substance that is oxidized has lost electrons

2 Fun Ways to Remember OIL RIG LEOGER or LEO the lion says GER �Oxidation �Losing �Is �Electrons is �Losing elections �Oxidation, �Reduction �Gaining �Is �Electrons is �Gaining electrons �Reduction

And now, the tricky part… �A substance that has been oxidized is called a reducing AGENT because it caused the other substance to take their electrons �A substance that has been reduced is called an oxidizing AGENT because it caused the other substance to give up its own electrons

�Br starts with 0 charge and ends with -1 The charge has gone down, because Br has gained electrons. �Mg starts with 0 charge and ends with +2 The charge has gone up, because Mg has lost electrons. �This means Br has been ______ and is the _______ agent. reduced oxidizing �This means Mg has been ______ and is the _______ agent. oxidized reducing

�Na starts with a +1 charge, ends with 0 charge Charge has gone down because it gained electrons �Cl starts with a -1 charge, ends with 0 charge Charge has gone up because it lost electrons �This means Na has been _______ and is the ______ agent. reduced oxidizing �This means Cl has been ______ and is the _______ agent. oxidized reducing

�Zn started with 0 charge, ended with +2 Charge has gone up because it lost electrons �Cu started with +2 charge, ended with 0 Charge has gone down because it gained electrons �SO 4 started and ended with -2, no electrons changed here �Zn has been oxidized and is the reducing agent �Cu has been reduced and is the oxidizing agent �SO 4 wasn’t really involved in this reaction then…