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Redox Processes(AHL) 19.1 (General information (Application (metal…
Redox Processes(AHL) 19.1
General information
non spontaneous reaction
happen in electrolytic cell
Electrical to chemical energy
electrolyte(free moving ion)
molten
aqueous
uses batery
negative: Cathode
Positive: Anode
diagram
Application
metal extraction
metal purification
metal electroplating
a process of caoting an object with a thin layer of matel using lectrolysis. The object to be coated should used as cathode. The anode should be made of the metal with which object is plated
LAW
Faraday's second law
Definition: the amount in mol of electron needed to discharge 1 mol of an ion at an electrode is equal to the charge on the ion, z.
Faraday's first law
Formula: Q= lt
t= duration of electrolysis, t will be directly proportional to the umber of electrons passing through external circuit.
I= current, I will be proportional to the number of electrons passing through external circuit
Definition: states that the mass of an element deposited during
the electrolysis is directly proportional to the quantity of electricity
passing through the electrolysis
1 Faraday=96500 c/mol
Factors affecting products of electrolysis
concentration
higher concentration: easily discharged (halide ion)
Type of electrode
active
involve in the process
inert
do not involve
Standard cell potential
positive: reduced
negative: oxidised
Lower position in ECS, easier to accept electron
electrolysis of aqueous solution
concentration of aqueous solution
dilute NaCl
Anode: water will be reduced
Cathode: water will be reduced
concentrated NaCl
Anode: chloride ion will be oxidized
Cathode: Water will be reduced
type of electrode
inert graphite electrode
CuSO4: Cu2+ and H20 to cathode, SO42- and H20 to anode
Cu2+ discharged to cathode and H20 discharged to anode (SO42- do not discharged)
active copper electrode
Cathode: copper reduced
anode: copper oxidised
electrolysis on water
Cathode: H+, anode: SO42- and H20 Cathode: H+ discharged and anode: H20 discharged (SO42- do not tend to oxidize)