Electroochemistry_I_Oxidation

Electroochemistry_I_Oxidation - +1 +2 Common oxidation...

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+2 -2 +1 +3 -1 +4 -3 Common oxidation states based on the periodic table. There are exceptions, a better procedure will be shown.
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OXIDATION STATES (REVIEW) • Use Periodic Table to get the oxidation state. • The composition is found from the conservation of charge. Example 1. What is the expected composition of lithium oxide? Li likes to be Li 1+ Li Æ Li 1+ 1e - (electron) O likes to be O 2- O + 2e - Æ O 2- Since the number of electrons is conserved: 2 (Li Æ Li 1+ 1e - ) Thus, 2Li Æ 2Li 1+ 2e - O + 2e - Æ O 2- 2Li + O Æ 2Li + + O -2 or Li 2 O Crossover rule LiO 1+ 2- Å oxidation state 2 1 = Li 2 O Example 2. What is the composition of magnesium nitride and magnesium oxide? MgN 2+ 3- 3 2 = Mg 3 N 2 MgO 2+ 2- 2 2 = MgO
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O X I D A T I O N N U M B E R O R O X I D A T I O N S T A T E NOTE, RULES ARE APPLIED IN ORDER. 1. Free elements are assigned an oxidation state of 0. 2. The sum of the oxidation states of all the atoms in a species must be equal to the net charge on the species. 3. The alkali metals (Li, Na, K, Rb, and Cs) in compounds are always assigned an oxidation state of +1. 4. Fluorine in compounds is always assigned an oxidation state of -1. 5. The alkaline earth metals (Be, Mg, Ca, Sr, Ba, and Ra) and also Zn and Cd in compounds are always assigned an oxidation state of +2. 6. Hydrogen in compounds is assigned an oxidation state of +1. 7. Oxygen in compounds is assigned an oxidation state of -2.
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N 2 O 5 HSO 4 1- H 2 O 2 ClO 2 NaH KO 2 NH 4 1+ KMnO 4 CH 2 OH XeO 2 F 2 ASSIGN AN OXIDATION STATE TO EACH ELEMENT Useful Names: Oxide O 2- -2 Peroxide O 2 2- -1 Superoxide O 2 - O -2 Æ N +5 H +1, O -2 Æ S +6 H +1 Æ O -1 O -2 Æ Cl +4 Na +1 Æ H-1 K +1 Æ O -½ H +1 Æ N -3 K +1, O -2 Æ Mn +7 H +1, O -2 Æ C -1 F -1, O -2 Æ Xe +6
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HOW TO ASSIGN OXIDATION STATE IF RULES DON’T DIRECTLY APPLY (F-1 Æ Cl-1) I. By analogy: PCl 4 + NH 4 Br CHClSH Cl -1, So P +5 H +1, Br -1, So N -3 H +1, Cl -1, S -2, So C +1 (F-1 Æ Br-1) (O-2 Æ S-2) Note, name can be an additional aid: The more electronegative element usually is listed second in the formula and in binary compounds is given the -ide suffix.
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Electroochemistry_I_Oxidation - +1 +2 Common oxidation...

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