Electrolytic Cells & Electrolytic Cells & Electrolysis Reactions Electrolysis Reactions Outside electrical source provides electrons Outside electrical source provides electrons that force a that force a non-spontaneous redox reaction non-spontaneous redox reaction . . Electricity “splits” a compound into it’s Electricity “splits” a compound into it’s neutral neutral elements elements Ex: H Ex: H 2 O(l) + electricity O(l) + electricity → H → H 2 (g) + O (g) + O 2 (g) (g)
23
Embed
Electrolytic Cells & Electrolysis Reactions Outside electrical source provides electrons that force a non-spontaneous redox reaction. Electricity “splits”
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Electrolysis Set Up Electrolysis Set Up Ex: NaCl(l)Ex: NaCl(l)
• Single Cell filled with Single Cell filled with electrolyte with +/- ionselectrolyte with +/- ions
• Attach battery to two electrodes.Attach battery to two electrodes.• Adds e- onto one electrode - Making it NEGATIVEAdds e- onto one electrode - Making it NEGATIVE• Pulls e- off one electrode - Making it POSITIVEPulls e- off one electrode - Making it POSITIVE
• Electrodes are made of an inert substance Electrodes are made of an inert substance (like platinum or graphite) that conducts. (like platinum or graphite) that conducts.
Which Way do the Ions Move?Which Way do the Ions Move?
To electrode ofTo electrode of
opposite chargeopposite charge
At neg. electrodeAt neg. electrode
electrons are gainedelectrons are gained by ion by ion
(reduction at CATHODE)(reduction at CATHODE)
At positive electrodeAt positive electrode
electrons are lostelectrons are lost by ion by ion
(oxidation at ANODE)(oxidation at ANODE)
What is Oxidized/Reduced?What is Oxidized/Reduced?
RememberRemember
AN OXAN OX
RED CATRED CATAnode is where oxidation happensAnode is where oxidation happens
Cathode is where reduction happensCathode is where reduction happens
Half Reactions & Net EquationHalf Reactions & Net Equation
Rxn at Anode:Rxn at Anode: (Ox) (Ox)ClCl-- Cl + 1e- Cl + 1e-Or more correctlyOr more correctly DIATOMIC!!!!!!DIATOMIC!!!!!!2Cl2Cl-- Cl Cl22 + 2e- + 2e-
Rxn at Cathode:Rxn at Cathode: (Red) (Red)NaNa+ + + 1e-+ 1e- Na Na(Multiply by 2 to balance electrons)(Multiply by 2 to balance electrons)
but there is a diatomic!but there is a diatomic!2H2H+1+1 + 2e- + 2e- HH22
Net:Net: 2H2H22O O 2H2H22 + O + O22
Electrolysis of Water (Animation)Electrolysis of Water (Animation)http://youtu.be/2t13S-KpGeE
Electrolysis of Water (Simple)Electrolysis of Water (Simple)http://youtu.be/HQ9Fhd7P_HA
ElectroplatingElectroplating
Electrolysis reaction Electrolysis reaction used to coat aused to coat asubstance with a thinsubstance with a thinlayer of metal.layer of metal.
Often coating is a lessOften coating is a lessreactive metal that isreactive metal that isnot easily oxidized ornot easily oxidized orcorroded.corroded.
ElectroplatingElectroplating
Negative ElectrodeNegative Electrode Is the OBJECT TO BE Is the OBJECT TO BE
PLATED PLATED so the positive metal ions so the positive metal ions
would go towards it and be would go towards it and be REDUCED.REDUCED.
It is the CATHODEIt is the CATHODE
Red:Red: Ag Ag++ + 1e- + 1e- AgAg00
ElectroplatingElectroplating
Positive ElectrodePositive ElectrodeMade of plating metalMade of plating metal It dissolves into solution as It dissolves into solution as
metal strip gets OXIDIZED.metal strip gets OXIDIZED. It is the ANODEIt is the ANODEThis replenishes the ions for This replenishes the ions for
You can now answer questions regarding You can now answer questions regarding the amount of a substance in moles or the amount of a substance in moles or grams that can be electroplated over a grams that can be electroplated over a certain amount of time.certain amount of time.
If 10 amps are run through a CuSOIf 10 amps are run through a CuSO4 4 solution for solution for 5 minutes, calculate the grams of Cu that will plate5 minutes, calculate the grams of Cu that will plateonto the spoon.onto the spoon.
We Know:We Know:1 mole e- = 96,500 coulombs1 mole e- = 96,500 coulombs# coulombs = # amps x seconds# coulombs = # amps x seconds
Red:Red: Cu Cu+2+2 + 2e- + 2e- CuCu00
2 moles electrons make 1 mole of Cu2 moles electrons make 1 mole of Cu00
1 mole Cu = 63.5 grams1 mole Cu = 63.5 grams
So….Let’s start hereSo….Let’s start here
# coulombs # coulombs = 10 amps x 300 seconds= 10 amps x 300 seconds
= 3000 coulombs= 3000 coulombs
3000 coul. x 3000 coul. x 1 mole e-1 mole e- x x 1 mole Cu1 mole Cu x x 63.5g Cu63.5g Cu = .987 grams = .987 grams