Electrochemistry
Reactivity
Wednesday, 19 March, 14
Reactivity
• Reactive metals are strong reducing agents
• Metals tend to lose their electrons and
form positive ions
• This is why metals will act as reducing
agents pushing their electrons onto
another substance
• More reactive metals lose their electrons
easier, hence they are stronger reducing
agents
Wednesday, 19 March, 14
Zinc + Copper (II) Sulfate Reaction
• First lets write out the chemical equation...
Wednesday, 19 March, 14
Zn(s) + CuSO4 (aq) --> Cu(s) + ZnSO4 (aq)
• This equation can be written as an ionic
equation without sulfate as it acts as a
spectator ion in the reaction.
•
• Zinc acted as the reducing agent, so it is the
Zn(s) + Cu2+ (aq)--> Cu(s) + Zn2+ (aq)
more reactive metal. Zinc forces the
copper ions to accept electrons.
Wednesday, 19 March, 14
What do you think will happen when we add copper
metal to a solution of zinc ions?
• There will be no reaction
• This is because Copper is not a strong
enough reducing agent to reduce the Zn2+
• This is another way of saying that it is a less
reactive metal, less able to push the
2+
electrons onto Zn
Wednesday, 19 March, 14
Reactivity Series
• Compares displacement reactions between
different metals and their ions to see which
ones are strong or weak reducing agents.
• It allows us to predict whether a redox
reaction will exist between a metal and the
ions of another metal.
Wednesday, 19 March, 14
Small Reactivity Series
Wednesday, 19 March, 14
Example!
• Refer to the reactivity series to predict
whether the following reactions will occur:
• a) ZnCl
•
Wednesday, 19 March, 14
2 (aq)
+ 2Ag(s) --> 2AgCl(s) + Zn(s)
b) 2FeCl3 (aq) + 3 Mg(s) --> 3MgCls(aq) + 2 Fe(s)
•
Wednesday, 19 March, 14
b) 2FeCl3 (aq) + 3 Mg(s) --> 3MgCls(aq) + 2 Fe(s)
Answers
• a) ZnCl + 2Ag --> 2AgCl + Zn
• This reaction would involve Ag reducing
2 (aq)
(s)
(s)
(s)
2+
Zn in
ZnCl2. But Ag is a weaker reducing
agent then Zn so this will not occur.
•
•
Wednesday, 19 March, 14
b) 2FeCl3 (aq) + 3 Mg(s) --> 3MgCls(aq) + 2 Fe(s)
This reaction involves Mg reducing Fe3+ in FeCl3.
Mg is a stronger reducing agent then Fe so this will
occur