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31 terms

LC Chem 1.5 Electrolysis

chemistry
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Electrolysis
The use of electricity to bring about a chemical reaction
Electrolyte
Liquid in which electrolysis takes place. Usually an ionic solution but it can also be a fused [melted] ionic compound
Direct current
Provides the energy necessary to create or discharge the ions in the electrolyte
Electrodes
Electrical conductors which link between the electrical circuit and the electrolyte
Inert
Electrodes which do not react with the electrolyte e.g. Graphite and Platinum
Active
Electrodes which react with electrolyte e.g. Copper and Iron
Anode
Positive electrode. Positive because the battery sucks electrons out of it.
Cathode
Negative electrode. Negative because the battery pumps electrons into it.
Anion
Negative ion. Named because it is attracted to the opposite charge of the anode
Cation
Positive ion. Named because it is attracted to the opposite charge of the cathode
Reduction
Reaction at cathode
H2O + 2 e- --> H2 + 2OH-
Equation at cathode
Hydrogen (H2)
Gas released at cathode
Base (OH- ions)
Acid or base at cathode
Oxidation
Reaction at anode
2H2O --> O2 + 4H+ + 4e−
Equation at anode
Oxygen (O2)
Gas released at anode
Acid (H+ ions)
Acid or base at anode
Graphite
Electrodes used for electrolysis of Sodium Sulphate and Universal Indicator
Purple
Colour at Cathode with Sodium Sulphate and Universal Indicator
Orange
Colour at Anode with Sodium Sulphate and Universal Indicator
Pink
Colour at Cathode with Potassium Iodide and Phenolphthalein
Brown
Colour at Anode with Potassium Iodide and Phenolphthalein
2I- --> I2 + 2e-
Equation at anode due to the oxidation of KI to brown Iodine
Electroplating
The process of covering the cathode in metal
Anode
Electrode which loses mass as copper dissolves off
Cu --> Cu2+ + 2e-
Equation at anode during copper electroplating
Cathode
Electrode which gains mass as Cu is deposited on it
Cu2+ + 2e- --> Cu
Equation at cathode during copper electroplating
Electrode potential
The tendency of a metal to lose electrons, i.e. the tendency for a metal to be oxidised
Electrochemical series
A list of elements in order of their standard electrode potentials: Pretty Sally Could Marry A Zulu In Lovely Honolulu Causing Many Strange Gazes (except for calcium)