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Redox Processes (AHL) 19.1 (General information (Application (metal…
Redox Processes (AHL) 19.1
LAW
Faraday's first law
Definition: states that the mass of an element deposited during the electrolysis is directly proportional to the quantity of electricity passing through the electrolysis.
Formula: Q= It Q:charge I:current , t:time(s)
1 Faraday= 96500 c/mol
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.
example of electrolysis of aqueous solution.
type of electrode
Active copper electrodes.
Cathode: copper reduced.
Anode: copper oxidised.
innert graphite electrode.
CuSO4 ; Cu2+ and H2O to cathode, SO42- and H2O to anode.
Cu2+ discharged to cathode and
H2O discharged to anode. (SO42- not discharged)
electrolysis on water
dilute sulphuric acid
Cathode: H+, Anode: SO42- and H2O .
Cathode: H+ discharged and
Anode: H20 discharged (SO42- do not tend to oxidize
concentration of aqueous solution
concentrated NaCl
Cathode: water will reduced. Anode: chloride ion will oxidised.
dilute NaCl
cathode: water will be reduced
Anode: water will be oxidised.
Factors affecting products of electrolysis.
Standard cell potential.
.
positive: reduced
negative: oxidised.
concentration
higher concentration: easily discharged ( halide ion)
Type of electrode.
active
involve in the process
inert.
do not involve.
General information
non spontaneous reaction
happen in electrolytic cell
Electrical to chemical energy
electrolyte(free moving ion)
aqueous
molten
uses battery
positive: Anode
Negative: Cathode.
Application
metal extraction.
metal purification
metal electroplating
diagram