Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Electrochemistry Lesson 3 Oxidation Numbers Ho Ho Ho Silver crystals on a copper frame Oxidation Numbers HV2O4- V6+ Is the above equation oxidation or reduction? Oxidation numbers are assigned numbers that are used to determine if oxidation or reduction has occurred. Rules for Oxidation Numbers 1. Oxidation # All elements are zero: N2 0 Pb 0 Na 0 O2 0 Rules for Oxidation Numbers 2. Oxidation # Monatomic Ions are their charge Na+ +1 Br- -1 MgSO4 +2 Al2S3 -2 Rules for Oxidation Numbers 3. Oxidation # O in a compound is -2 exception: peroxides -1 Na2O CO2 O2 CH3COOH HOOH -2 -2 0 -2 -1 exception Rules for Oxidation Numbers 4. Oxidation # H in a compound is +1 exception: metal hydrides -1 H2O C12H22O11 H2 NaH +1 +1 0 -1 Rules for Oxidation Numbers 5. The sum of the oxidation numbers must equal the charge oxidation #s +6 -2 SO4 Total charge 2- +6 -8 = -2 -2 x 4 oxidation #s +5 -2 PO4 Total charge 3- +5 -8 = -3 oxidation #s +6 -2 Cr2O7 Total charge 2- +12 -14 = -2 12 / 2 +2 Ca(NO3)2 +1 +7/ 2 -2 Na2C4O8 +2 +14 -16 = 0 CH3COOH Rewrite 0 +1 -2 C 2 H4 O2 0 +4 -4 = 0 +2 -2 +1 Zn(OH)42+2 -8 +4 = -2 +1 +4 -1 H2PtCl6 +2 +4 -6 = 0 +1 +3 -2 H3PO3 +3 +3 -6 = 0 +3 +5 -2 Al(NO3)3 +3 +15 -18 = 0 +1 -1 -2 Na2O2 +2 -4 = 0 -2 Exception - does not work, O must be -1 +2 +1 -1 CaH2 +2 -2 +2 =0 Exception - does not work, H must be -1 Fe(H2O)5(OH)2+ 0 -1 Fe(H2O)5(OH)2+ ? + 0 -1 = +2 +3 0 -1 Fe(H2O)5(OH)2+ +3 + 0 -1 = +2 Oxidation Numbers Increase +6 +3 HV2O4- V6+ Is the above equation oxidation or reduction? If the oxidation number increases it is oxidation. Using Oxidation Numbers If the oxidation number of the central atom increases going from left to right, its oxidation. +3 Increase is oxidation ClO2oxidation reducing agent 4 electrons lost +7 ClO4- Using Oxidation Numbers If the oxidation number of the central atom decreases going from left to right, its reduction. +5 decrease is reduction NO3reduction 2 electrons gained oxidizing agent +3 HNO2 Label the oxidizing agent and the reducing agent. +7 ReO4- + +1 IO- Reduced Oxidized Ox Agent Red Agent +5 IO3- + 0 Re Label the oxidizing agent and the reducing agent. +3 +5 +5 +2 3As2O3 + 4NO3- + 7H2O + 4H+ 6H3AsO4 + 4NO oxidized reduced red agent ox agent Numa Numa