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Types of Chemical Reactions and Solution Stoichiometry

Types of Chemical Reactions and Solution Stoichiometry. Oxidation and Reduction (Redox). Electrons are transferred. Spontaneous redox rxns can transfer energy Electrons (electricity) Heat. Non-spontaneous redox rxns can be made to happen with electricity. Oxidation and Reduction.

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Types of Chemical Reactions and Solution Stoichiometry

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  1. Types of Chemical Reactionsand Solution Stoichiometry

  2. Oxidation and Reduction (Redox) • Electrons are transferred • Spontaneous redox rxns can transfer energy • Electrons (electricity) • Heat • Non-spontaneous redox rxns can be made to happen with electricity

  3. Oxidation and Reduction An old memory device for oxidation and reduction goes like this… LEO says GER LoseElectrons = Oxidation GainElectrons = Reduction

  4. Oxidation Reduction Reactions(Redox) Each sodium atom loses one electron: Each chlorine atom gains one electron:

  5. LEO says GER : Lose Electrons = Oxidation Sodium is oxidized Gain Electrons = Reduction Chlorine is reduced

  6. Rules for Assigning Oxidation NumbersRules 1 & 2 • The oxidation number of any uncombined element is zero 2. The oxidation number of a monatomic ion equals its charge

  7. Rules for Assigning Oxidation NumbersRules 3 & 4 3.The oxidation number of oxygen in compounds is -2 4. The oxidation number of hydrogen in compounds is +1

  8. Rules for Assigning Oxidation Number Rule 5 5. The sum of the oxidation numbers in the formula of a compound is 0 2(+1) + (-2) = 0 H O (+2) + 2(-2) + 2(+1) = 0 Ca O H

  9. Rules for Assigning Oxidation NumbersRule 6 6. The sum of the oxidation numbers in the formula of a polyatomic ion is equal to its charge X + 4(-2) = -2 S O X + 3(-2) = -1 N O  X = +5  X = +6

  10. Reducing Agents and Oxidizing Agents • The substance reduced is the oxidizingagent..loses electron • The substance oxidized is the reducingagent..gains electron Sodium is oxidized – it is the reducing agent Chlorine is reduced – it is the oxidizing agent

  11. Trends in Oxidation and Reduction • Active metals: • Lose electrons easily • Are easily oxidized • Are strong reducing agents • Active nonmetals: • Gain electrons easily • Are easily reduced • Are strong oxidizing agents

  12. Redox Reaction Prediction #1

  13. Redox Reaction Prediction #2

  14. Not All Reactions are Redox Reactions Reactions in which there has been no change in oxidation number are not redox rxns. Examples:

  15. BALANCING OXIDATION/REDUCTION REACTIONS • Split the equation into two halves (oxidation/reduction). • Balance one of the half–equations with respect to both atoms and charge. • Balance the other half • Balance the half-equations to eliminate electrons

  16. VERY IMPORTANT! • If you mix two volumes, to find the new molarity divide by total volume!

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