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Chapter 19 Oxidation-Reduction Reactions Pg. 595. Oxidation- valence electrons are lost Reduction- valence electrons are gained Rules for determining the oxidation number of an element (pg. 595) Practice assigning Oxidation numbers (pg. 612 #7 a-j) (pg.612 #6). Oxidation-Reduction Reaction.
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Chapter 19Oxidation-Reduction Reactions Pg. 595 • Oxidation- valence electrons are lost • Reduction- valence electrons are gained • Rules for determining the oxidation number of an element (pg. 595) • Practice assigning Oxidation numbers (pg. 612 #7 a-j) (pg.612 #6)
Oxidation-Reduction Reaction • Also called-Redox • Transfer of electrons • One cannot happen without the other. Oxidation Reduction IsIs LosingGaining Oxidation #increases Oxidation # decreases
Remember:Oil Rig • Determine Oxidation or Reduction • (pg. 612 #4) • Pg. 599 #3 a. is an example. Try b-e on your own for practice. • Practice Pg. 605 #1 • Pg. 612 #2 a-i,3,5 a-c,17 a-e,18
Hon Chem Ch 20 Pg617Electrochemical Cells • AKA batteries • Pg607 Zn is good reducing agent (gets oxidized, loses electrons, ox# goes up) • Cu is good oxidizing agent (gets reduced, gains electrons, ox# goes down)
Parts and Types of BatteriesPg618-22 1. Zinc-Carbon Dry Cell a. big, used in flashlights, C and D batteries b. Zn container – anode, negative, becomes + as loses electron c. C rod in center – cathode, + bump on end of battery, becomes negative as gains electrons
2. Alkaline Batteries – Pg 621 a. smaller, AA and AAA, cameras, remotes b. Zn and KOH instead of Zn and C • Hg Batteries – Pg 622 a. tiny, hearing aids, watches b. Zn, KOH, Steel, HgO
Corrosion and PreventionPg623-24 • Fe is oxidized, loses electrons, forms rust • Salt and acid speed up the oxidation • Zn coating prevents oxidation due to Pg607, called galvanizing • Electric potential difference = volts (how hard electricity pushes thru wire)
Recharging BatteriesPg629-31 • Voltaic cell – battery making electricity, anode gives electrons to cathode • Electrolytic cell – battery when being recharged, storing electricity, direct current source forces cathode to give electrons back to anode • DC sources - wall charger with diode to change AC to DC, car alternator, other battery (jumping a car) AC – alternating currect, flows back & forth, generators, walls. DC – direct current, flows in one direction, batteries • Can be recharged as long as enough products to act as reactants to reverse reaction, corrosion is loss of products/reactants so can’t recharge after corroded