ES 3- Manufacturing Chlorine Flashcards
Define electrolysis
Breaking down of a compound using electricity
Is the anode positively or negatively charged?
Positively charged
In electrolysis, cations migrate to…
Cathode
In electrolysis, anions migrate to…
Anode
Which line in symbol for cell/battery in electrolysis represents the negative terminal?
Shorter line
Define electrolyte
- molten or aqueous salt that has ions that are free to move and carry a current
Does oxidation or reduction occur at anode?
Oxidation, negative ions lose electrons
In electrolysis of molten lead bromide, what will occur at anode?
2Br-(l) Br2(g) + 2e- Bromide gas (orange) formed
Why electrolysis in an aqueous solution different to in aqueous solution?
- water can be reduced and oxidised
Predict products of electrolysis of molten salt on each electrode
At cathode: metal
At anode: non-metal, apart from hydrogen
Give equation for oxidation of water at anode
2H2O(l) O2(g) + 4H+(aq) + 4e-
In electrolysis of an aqueous solution, in which circumstances would water be oxidised at anode instead of other negative ions?
- sulfates and nitrates are less easily oxidised than water, oxygen gas would be formed at anode
What is formed at anode in aqueous solutions, if halide ions are present?
- halogen, halides more easily oxidised than water
What occurs at anode if hydroxide ions are present in aqueous solution?
Hydroxide ions are oxidised, forming oxygen
Does oxidation or reduction occur at cathode?
Reduction, positive ions gain electrons
In electrolysis of molten lead bromide, what occurs at cathode?
Pb2+(l) + 2e- Pb(s)
- lead metal formed
Write equation of reduction of water
2H20(l) + 2e- 2OH-(aq) + H2(g)
Hydrogen gas produced
In what circumstances would water be reduced at cathode instance of metal ions?
If solution contains ions from group 1, 2 or aluminium
- are very reactive and will stay as ions
What occurs at cathode if solution is acid?
H+ ions re reduced forming H2 gas
Define inert
Chemically inactive
What occurs in electrolysis of copper sulphate solution with a copper anode?
- at anode, copper atoms are oxidised forming copper ions, so anode reduces in mass
- at cathode, copper ions are reduced forming copper atoms, so copper is deposited and cathode is plated
In electrolysis of copper sulphate solution and copper anode, what happens to the concentration of the solution?
- remain constant, as copper metal is turned to ions at anode, and ions are turned to metal at cathode
