OxidReduction - ELECTROCHEMISTRY Electrochemistry involves...

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Unformatted text preview: ELECTROCHEMISTRY Electrochemistry involves the relationship between electrical energy and chemical energy. OXIDATION-REDUCTION REACTIONS SPONTANEOUS REACTIONS Can extract electrical energy from these. Examples: voltaic cells, batteries. NON-SPONTANEOUS REACTIONS Must put in electrical energy to make them go. Examples: electrolysis, electrolytic cells. QUANTITATE REACTIONS OXIDATION-REDUCTION Oxidation = loss of electrons. An oxidizing agent is a substance that causes oxidation (and is itself reduced). Reduction = gain of electrons. A reducing agent is a substance that causes reduction (and is itself oxidized). LAnOx and GRedCat! LAnOx: L ose electrons / An ode / Ox idized GRedCat G ain electrons / Red uced / Cat hode Single Displacement Reactions Zn(s) + CuSO 4 (aq) ! ZnSO 4 (aq) +Cu(s) Ionic equation: Net ionic equation What is oxidized? What is reduced? What is the oxidizing agent? What is the reducing agent? Oxidation reduction reactions Rules for determining Oxidation States 1. Oxidation state of atom in elemental form is zero. e.g. Cl 2 O 2 P 4 C(s) S 8 2. The oxidation number of a monatomic ion equals its charge. 3. Some elements have common oxidation numbers that can be used as reference in determining the oxidation numbers of other atoms in the compound. Alkali metals +1 Alkaline earth metals +2 Fluorine 1 O usually 2 (peroxides (-1) & superoxides possible) H usually +1 (Hydrides: metal-H compounds (1)) Cl, Br, I almost always 1 4. Sum of oxidation numbers is equal to overall charge of molecule or ion: For a neutral compound the sum of oxidation numbers equals zero. For a polyatomic ion, the sum of the oxidation numbers is equal to the charge on the ion. 5. Shared electrons are assigned to the more electronegative atom of the pair: more electronegative atom will have a negative Single Displacement Reactions Zn(s) + CuSO 4 (aq) ! ZnSO 4 (aq) +Cu(s) Ionic equation: Net ionic equation What is oxidized? What is reduced? What is the oxidizing agent? What is the reducing agent? Oxidation reduction reactions Rules for determining Oxidation States 1. Oxidation state of atom in elemental form is zero. e.g. Cl 2 O 2 P 4 C(s) S 8 2. The oxidation number of a monatomic ion equals its charge. 3. Some elements have common oxidation numbers that can be used as reference in determining the oxidation numbers of other atoms in the compound. Alkali metals +1 Alkaline earth metals +2 Fluorine 1 O usually 2 (peroxides (-1) & superoxides possible) H usually +1 (Hydrides: metal-H compounds (1)) Cl, Br, I almost always 1 4. Sum of oxidation numbers is equal to overall charge of molecule or ion: For a neutral compound the sum of oxidation numbers equals zero....
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This note was uploaded on 07/23/2008 for the course CHEM 112 taught by Professor Vandersluys,lorschmid,kylem during the Fall '07 term at Pennsylvania State University, University Park.

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OxidReduction - ELECTROCHEMISTRY Electrochemistry involves...

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