In this topic,I had jumped into a subtopic ELECTROLYSIS between electrolytic cell, voltaic cell and Daniell cell since I know that an ordinary student who's going to take chemistry subject just like me found difficulty at this electrolysis topic. Electrolysis in electrolytic cell can undergo in molten states and in aqueous solution since not in solid states because there are no freely moving ions of a solid states.
electrolytic cells
in electrolytic cells, change of energy is from ELECTRICAL to CHEMICAL energy.
anode(+ terminal) will attract anion(- charged ion)
in molten :-
example: (by using molten lead(II)bromide as an electrolyte)
since there is no presence of any aqueous solution at all this is thing happenned:-
ions presents:-
at anode = Br- at cathode= Pb2+
half equations:-
at anode = at cathode=
Br2 -> 2Br- + 2e- Pb2+ + 2e- -> Pb
Product:-
at anode = at cathode=
bromine gas Lead metal
in aqueous solutions:-
in aqueous solutions,element at anode and cathode is placed under the low positions in the Electrochemical Series.
cations:- anions:-
K+ F-
Na+ SO 2-
Ca2+ NO3 -
Mg2+ Cl-
Al3+ Br-
Zn2+ I-
Fe2+ OH-
Sn2+
Pb2+
H+
Cu2+
Ag+
example:-(by using copper (II) sulphate solutions as an electrolyte)
all ions present:-
at anode = at cathode =
SO4 2- , OH- Cu 2+ , H+
half equation:-
at anode = at cathode =
4OH- -> 2 H2O + O2 + 4e- Cu2+ + 2e- -> Cu
observation:-
at anode = at cathode =
bubbles of colourless gas release brown solid is deposited
*observation on CuSO4 solution =
blue colour of CuSO4 solutions become light blue since the colour intensity of CuSO4 decreases.
Product:-
at anode = at cathode =
oxygen gas copper metal
Electrolysis in aqueous solution can undergoes another two more elements which are:-
1. concentration of ions
2. types of electrodes
1. concentration of ions
