Electrochemistry - Battery cells Sec 4 Chemistry 2010
Jan 06, 2016
Electrochemistry - Battery cells
Sec 4 Chemistry 2010
Metals of the reactivity series
Arrange the highlighted metals according to their reactivity.
Displacement Reactions More reactive metal (Cu) + Less reactive metal ion (Ag+)
Displacement ReactionsK
Na
Ca
Mg
Al
Zn
Fe
Sn
Pb
Cu
Ag
Au
Cu(s) + Ag+ Cu2+ + Ag(s)
Cu(s) Cu2+
Ag+ Ag(s)
+ 2e-
e- +
Half-reactions
oxidation
reduction
Displacement ReactionsK
Na
Ca
Mg
Al
Zn
Fe
Sn
Pb
Cu
Ag
Au
Zn(s) + Cu2+ Cu(s) + Zn2+
Zn(s) Zn2+
Cu2+ Cu(s)
+ 2e-
2e- +
Half-reactions
oxidation
reduction
Half-reactions
e-
e-
e-
e-e-
Oxidation:Zn Zn2+ + 2e-
Reduction:
Cu2+ + 2e- Cu
Zn
Cu2+
Electrodes
Zn
A half-cell
Cu2+
Doesn't react with Zn, e.g. Zn2+
Doesn't react with Cu2+, e.g. Cu
Electrodes
Half-cells A half-cell contains half of the redox reaction.
The anode is where the oxidation half-reaction takes place. The cathode is where the reduction half-reaction takes
place. What properties must the two electrodes have?
Note: by convention, we draw the anode half-cell on the left hand side.
Is the circuit complete?
Zn
Cu2+?
?
Zn2+
Cue-
e-
oxidation
anode
Zn Zn2+ + 2e-
cathode
reductionCu2+ + 2e- Cu
The salt bridge Allows the flow of ions between the two half-cells.
Consists of an electrolyte: Doesn't react with the chemical reagents in the cell. Example: NaNO3 or KNO3
The salt bridge
Zn
Cu2+?
?
Zn2+
Cue-
e-
saltbridge
anions (A-)
cations (C+)
oxidation
anodecathode
reduction