Slide 1

Topic: Electrolytic Cell Do now: p.19 in packet, cross out # 19 and do # 20 and #21. must label anode/cathode

Slide 2

Chemical rxns can produce electricity = galvanic (voltaic) cell OR Electrical energy used to carry out chemical reactions= electrolytic cell Electrolytic Cell need electrical energy so NONSPONTANEOUS

Slide 3

Chemical Potential Energy Electrical Potential Energy Galvanic Cell Electrolytic Cell Galvanic cell is a battery Electrolytic cell needs a battery

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Electrolytic Cells Nonspontaneous Need battery or power supply Consumes energy = endothermic

Slide 5

Whats the difference? anode catode Battery in one. Electrons in galvanic flowing from to + Electrons in electrylic flowing from + to - Electrolytic Cell a Fat Red Cat ate an Ox Use Table J, but opposite More active metal = cathode = negative Less active metal = anode = positive Galvanic Cell A Fat Red Cat ate an Ox Use Table J More active metal = anode = negative Less active metal = cathode = positive e - e - e -

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NONSPONTANEOUS e - flow Anode to Cathode But from + to (opposite then wed think) Thats why we use the battery SPONTANEOUS e - flow Anode to Cathode from to + (just like wed think) Thats why its spontaneous e - e - e -

Slide 7

A POX A POX on Electrolytic Cells Anode Positive Oxidation A pox = a disease And electrolytic cell behave differently like they are diseased?!

Slide 8

Various types of electrolytic cells 1.Fused Salt Cells used to purify metals (Fused means melted = molten salt cell) Add NaCl (s) and melt it Now NaCl (l) Why melt it?! Why add CaCl 2 (s)??! Na +1 is reduce to Na(l) Na(l) is less dense then NaCl(l) so it floats on top 20,000 tons of Na are produce this way in the US every year Molten b/c need ions Lowers MP dont need as much heat

Slide 9

Fused Salt Cell (Molten salt cell) (l) + Na + Cl - Na + Cl - - Na + + 1e - NaCl - + Cl + 1 e - Gain electron So reduced So cathode lose electron So oxidized So anode BUT WAIT SOMETHING IS WRONG WITH OUR ANODE 2 22 e- e- e- e-e- e- e- e-

Slide 10

Various types of electrolytic cells 2. Electroplating A layer of a second metal is deposited on the metal electrode that acts as the cathode Used to enhance the appearance of metal objects and protect them from corrosion.

Slide 11

Various types of electrolytic cells 2. Electroplating cathode = object to be plated anode - made of metal want to plate on object solution: contains ions of plating metal

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NO 3 - + - Ag + + 1e - Ag Gain electron So reduced So cathode Ag Ag + + 1e - lose electron So oxidized So anode e- e- e- e-e- e- e- e-

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3. Electrolysis of H 2 O H 2 is produced at one electrode, O 2 at the other. 2H 2 O + energy 2H 2 + O 2 Can you tell from the picture which electrode is producing H 2 ?

Slide 14

What do every one of these have in common?