Electrochemistry Flashcards
What happens when an electric current is passed through a molten ionic compound
The compound decomposes - this is called electrolysis
Do molten ionic componds in solution undergo electrolysis (decompositon of of the comound when electricuty is passed thought it.)?
Yes
Define electrolysis
The brakdown of an ionic compound (molten or in aqueous solution) by the passage of electricity.
what is the name of the vessel in which electrolysis takes place?
An electrolysis cell.
What equipment does eletroysis need?
power supply
anode (positve electrode)
Cathode (negative electrode)
Electrolyte (the molten / aqueous soltion of a compound)
Beaker
Define an electrorode
A rod of metal or graphite which leads an electric current to or from an electrolyte.
Electrolyte
An ionc compound which conducts electricity when molten or dissolved in water.
Define an anode
A positive electrode
Define a cathode.
A negative electrode.
Define an anion
A negative ion.
Define a cation.
A positive ion.
When molten lead bromide is the electrolyte what forms at the anode and cathode?
Anode: bromine
Cathode: lead
When dilute sulphuric acid is the electrolyte what forms at the anode and cathode?
Anode: oxygen
Cathode: hydrogen
When concentrated hydrochloric acid is the electrolyte what forms at the anode and cathode?
Anode: chlorine
Cathode: hydrogen
When concentrated acqueous sodium chloride is the electrolyte what forms at the anode and cathode?
Anode: chlorine
Cathode: hydrogen
When molten zinc chloride is the electrolyte what forms at the anode and cathode?
Anode: chlorine
Cathode: zinc
When molten sodium iodide is the electrolyte what forms at the anode and cathode?
Anode: iodine
Cathode: sodium
What is an ionic half equation?
An equation balanced by electrons which shows either oxidation or reduction.
Define electroplating
The coating of the surface of one metal with a layer of another by an electrolytic reaction.
Define electrochemical cell
A source of electricalchemical energy where two metals of differnt reactivity dipping into an electrolyte are connected via an external circuit.
What are the equations at the anode and cathode for
Cathode reaction: Pb2+ + 2e- becomes Pb
Anode reaction: 2Br- becomes Br2 +2e-
What are the equations at the anode and cathode for concentrated aqueous NaCl?
Cathode reaction: 2H+ + 2e- becomes H2
Anode reaction: 2Cl- becomes Cl2 + 2e-
What are the equations at the naode and cathode for dilute aqueous NaCl?
Cathode reaction: 2H+ + 2e- becomes H2
Anode reaction: 4OH- becomes O2 + 2H2O + 4e-
What are the equations at the anode and cathode for concentrated aqueous CuSO4?
Cathode reaction: Cu2+ + 2e- becomes Cu
Anode reaction: 4OH- becomes O2 + 2H2O + 4e-
What are the equations at the anode and cathode for concentrated aqueous HCl?
Cathode reaction: 2H+ +2E- becomes H2
Anode reaction: 2Cl- becomes Cl2 + 2e-
What are the equations at the anode and cathode for dilute aqueous H2SO4?
Cathode reaction: 2H+ +2e- becomes H2
Anode reaction: 4OH- becomes O2 +2H2O + 4e-
why can electrolysis only take place in molten or aqueous salts?
Molten salts:
Particles present are ions eletroysis can only take place when the salt is molten and so that the ions separate from each other and are free to move.
Aqueous solutions:
When salts dissolve in water they separate into their ions and are free to move.
What are formed at the cathode (negative electrode):
metals and hydrogen.
This is because their ions are positively charged and opposites attract.
What are formed at the anode (positive electrode):
non metals.
This is because their ions are negatively charged and opposites attract.
for compound formed of a metal and non metal which material goes to the anode and cathode?
metal goes to cathode
non metal goes to anode
What is the term for the reaction at the anode?
A oxidation reaction because electrons are lost.
What is the term for the reaction at the cathode?
A reduction reaction because electrons are gained.
Does a anode have positive or negative charge?
Positive.
Does a cathode have positive or negative charge?
Negative.
What haapens when the anode is reactive?
The metal
