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
Slide 4
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 -
Slide 6
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
Slide 12
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-
Slide 13
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 ?