1. Quick Review Basic Ideas about solubility in water as mentioned last weak-ionic materials generally dissociate in water Two quick rules (shortened from p. 120) cations: all salts of Group I ions and NH 4 + are soluble anions: salts of Cl -,Br -,I -,nitrate,perchlorate, acetate and sulfate are soluble –MX(aq) + M’X’(aq) => would ppt form? –Possibilities MX’ or M’X for a ppt to form both parts must not be on the list Suppose MX’ meets that criterion and will ppt MX + M’X’ => MX’ + M’X molecular M + (aq) + X - (aq) + M’ + (aq) + X’ - (aq) => MX’(s) + X - (aq) + M’ + (aq) total ionic M + (aq) + X’ - (aq) => MX’(s) Acids and bases –HA + B => A - + BH +

2. Oxidation and reduction Oxidation-loss of one or more electrons-the species being oxidized is the reducing agent Reduction-gain of one or more electrons-the species being reduced is the oxidizing agent redox process-transfer of electrons from the reducing agent to the oxidizing agent Tracking electrons is far more complex than tracking protons, as they don’t appear explicitly in the chemical formula Oxidation numbers are used to follow electrons

3. Oxidation Numbers You should be aware that oxidation numbers are designed to track electron changes, not the actual distribution of electrons in a complex species General Rules –Elements in their elemental forms have ON=0 –A monoatomic ion has an oxidation number equal to its charge –In an ionic compound, the oxidation numbers equal the ion charges. –In chemical compounds or polyatomic ions(there is a hierarchy here, a higher rule trumps a lower one) fluorine is always 1- H is 1+ except in metal hydrides where it is 1- oxygen is 2- except in peroxides(1-) or bound to F other halogens are 1- except for interhalogen compounds or when bound to oxygen the sum of the oxidation numbers must equal the charge on the compound or ion. What are the oxidation numbers in the following: CO 2, MnO 4 -, HClO 4, H 2 CO, FeSO 4

4. Redox Reactions It is usually possible to separate a redox process into half reactions based upon oxidation number changes MnO 4 - + Fe 2+ => MnO 2 + Fe 3+ CH 3 OH + Cr 2 O 7 2- => H 2 CO + Cr 3+ We can write “generic” equations of the type RA + OA => OA + RA similar to that done for acids and bases

5. Looking from both sides In the areas of precipitation, acids-bases and redox, the processes can be viewed either left to right or right to left. –M + (aq) + X - (aq)  MX(s) –HA(aq) + B(aq)  A - (aq) + HB + (aq) –RA + OA  OA + RA

6. A few acid-base details In the reaction below HA and A - is a conjugate acid-base pair as is B and HB + HA(aq) + B(aq)  A - (aq) + HB + (aq) Neutral acid-base species alkali metals and alkaline earths and the conjugate bases of the strong monoprotic acids Cl -, Br -, I -, NO 3 - and ClO4 -