Topic Electrolytic Cell Do now p 19 in

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Topic: Electrolytic Cell Do now: p. 19 in packet, cross out # 19 and

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

 • Chemical rxns can produce electricity = galvanic (voltaic) cell OR • Electrical

• 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

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

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

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

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

What’s the difference? Battery in one. Electrons in galvanic flowing from – to +

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

NONSPONTANEOUS e- flow Anode to Cathode But from + to – from – to

NONSPONTANEOUS e- flow Anode to Cathode But from + to – from – to + (opposite then we’d think) (just like we’d think) That’s why we use the battery That’s why it’s spontaneous e- e-

A POX on Electrolytic Cells • Anode – Positive – Oxidation A pox =

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

Various types of electrolytic cells 1. Fused Salt Cells – used to purify metals

Various types of electrolytic cells 1. Fused Salt Cells – used to purify metals (Fused means melted = molten salt cell) • Add Na. Cl (s) and melt it • Now Na. Cl (l) • Why melt it? ! Molten b/c need ions • Why add Ca. Cl 2(s)? ? ! Lowers MP – don’t need as much heat • Na+1 is reduce to Na(l) • Na(l) is less dense then Na. Cl(l) so it floats on top • 20, 000 tons of Na are produce this way in the US every year

Fused Salt Cell (Molten salt cell) + - e- e- lose electron So oxidized

Fused Salt Cell (Molten salt cell) + - e- e- lose electron So oxidized So anode 2 Cl- + Cl 2+ 12 e- Gain electron So reduced So cathode Na+ (l) Cl- Na+ + 1 e- Na Na+ Cl- BUT WAIT SOMETHING IS WRONG WITH OUR ANODE

Various types of electrolytic cells 2. Electroplating A layer of a second metal is

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.

Various types of electrolytic cells 2. Electroplating • cathode = object to be plated

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

+ e- e- lose electron So oxidized So anode Ag Ag+ + 1 e-

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

3. Electrolysis of H 2 O H 2 is produced at one electrode, O

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

What do every one of these have in common?

What do every one of these have in common?