9. Electrochemistry - Electrochemistry Chapter 9 Oxidation...

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Electrochemistry Chapter 9
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Oxidation number The number of charges, the atom would have - in a molecule (or an ionic compound) - if electrons were completely transferred . When a substance oxidize , it lose e - So, the oxidation number increase Another substance, gain the e - So, the oxidation number reduce Ox idation Red uction Al Al 3+ + 3e - Mg 2+ + 2e- Mg
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The definition of oxidation reduction describe as lose and gain e- Can apply to MgO (ionic compound) Mg 2+ and O 2- Can we apply redox to CO 2 ? In covalent compound , no electrons are actually transferred in formation of these compound. But , it is convenient to treat the reaction of covalent compound as redox reaction
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1. Free elements (uncombined state) have an oxidation number of zero. Na, Be, K, Pb, H 2 , O 2 , P 4 = 0 1. In monatomic ions , the oxidation number is equal to the charge on the ion. Li + = +1 ; Fe 3+ = +3 ; O 2- = -2 1. The oxidation number of oxygen is usually –2 . In H 2 O 2 and O 2 2- it is –1 . For 2 identical atoms compound, e- are split equally For 2 different atoms compound, share e- are assigned completely to atom that has stronger attraction for electron . (CO 2 ) Rules of OXIDATION NUMBER
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1. The oxidation number of hydrogen is +1 except when it is bonded to metals in binary compounds . In these cases, its oxidation number is –1 . 6. The sum of the oxidation numbers of all the atoms in a molecule or ion is equal to the charge on the molecule or ion. 1. Group IA metals are +1 , IIA metals are +2 and fluorine is always –1 . HCO 3 - O = -2 H = +1 3x( -2 ) + 1 + ? = -1 C = +4 Oxidation numbers of all the atoms in HCO 3 - ?
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Assign oxidation states to all atoms in the following. a) CO 2 b) SF 6 c) NO 3 - # write the actual charge on ion as n+ / n- (number before plus / minus sign) # write oxidation state as + n / -n
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is the study of the interchange of chemical E and electrical E. The interchange of E can be explained by: 1) The generation of Electrical Current from a spontaneous Chemical reaction 2) The use of Electrical Current to produce Chemical Change Galvanic Cells Electrolysis Electrochemistry
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Electrochemistry concern of 2 process Ox idation reaction = Red uction reaction + Redox reaction A process of e- transfer Reduce oxidation number Increase oxidation number LEO
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This note was uploaded on 04/10/2010 for the course CHM CHM101 taught by Professor Woljaong during the Fall '07 term at Multimedia University, Cyberjaya.

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9. Electrochemistry - Electrochemistry Chapter 9 Oxidation...

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