Lecture 5 Reduction-Oxidation Reactions Redox Reduction-Oxidation Reactions Redox.
Chapter 19 Oxidation-Reduction Reactions Pg. 595
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Transcript of Chapter 19 Oxidation-Reduction Reactions Pg. 595
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
Is Is
Losing GainingOxidation #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 Pg 655Electrochemical Cells
• AKA batteries • Pg 643 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 BatteriesPg 656-9
1. Zinc-Carbon Dry Cella. big, used in flashlights, C and D batteriesb. Zn container – anode, negative, becomes + as loses electronc. C rod in center – cathode, + bump on end
of battery, becomes negative as gains electrons
2. Alkaline Batteriesa. smaller, AA and AAA, cameras, remotes
b. Zn and KOH instead of Zn and C 3. Hg Batteries
a. tiny, hearing aids, watchesb. Zn, KOH, Steel, HgO
Corrosion and PreventionPg 661-2
• Fe is oxidized, loses electrons, forms rust• Salt and acid speed up the oxidation• Zn coating prevents oxidation due to Pg 643,
called galvanizing• Electric potential difference = volts (how hard
electricity pushes thru wire)
Recharging BatteriesPg 667-9
• 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)
• 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 Pg 669**do redox rxn for car battery