Chemistry Reference
In-Depth Information
Figure 10.8 shows what happens when a piece of
zinc metal is left to stand in a solution of copper(ii)
ii
)
nitrate. The copper(ii)
ii
) nitrate slowly loses its blue
colour as the zinc continues to displace the copper
from the solution and eventually becomes colourless
zinc nitrate.
zinc
Questions
1
Predict whether or not the following reactions will take
place:
a
magnesium
+
copper(
ii
) oxide
b
iron
+
aluminium oxide
c
calcium
+
magnesium oxide.
Complete the word equations and write balanced
chemical and ionic equations for those reactions which
do take place.
2
Predict whether or not the following reactions will take
place:
a
magnesium
+
calcium nitrate solution
b
iron
+
copper(
ii
) nitrate solution
c
copper
+
silver nitrate solution.
Complete the word equations and write balanced
chemical and ionic equations for those reactions which
do take place.
3
How could you carry out a series of reactions between
metals and solutions of their nitrates to establish a
reactivity series?
4
The data below was obtained by carrying out
displacement reactions of fi ve metals with the nitrates of
the same fi ve metals. Strips of each metal were placed in
solutions of the other four metals' nitrate solutions.
+
copper(
ii
)
nitrate
Cu(NO
3
)
2
(
aq
)
zinc nitrate
+
copper
→
Zn(
s
)
+
Zn(NO
3
)
2
(
aq
)
+
Cu(
s
)
→
Nitrates
A
B
C
D
E
A
—
✓
✓
✓
✗
B
✗
—
✗
✗
✗
C
—
✗
✓
✓
✗
D
✗
✓
✗
—
✗
E
—
✓
✓
✓
✓
✓
= metal displaced
✗
= no reaction
Put the fi ve metals
A
-
E
in order of their reactivity using
the data above.
Figure 10.8
Zinc displaces copper.
●
Identifying metal ions
When an alkali dissolves in water, it produces
hydroxide ions. It is known that most metal
hydroxides are insoluble. So if hydroxide ions from a
solution of an alkali are added to a solution of a metal
salt, an insoluble, often coloured, metal hydroxide is
precipitated from solution (Figure 10.9).
Let's take the example of iron(
iii
) chloride with
sodium hydroxide solution:
iron(
iii
)
chloride
FeCl
3
(
aq
)
The ionic equation for this reaction is:
zinc
Zn(
s
)
+
+
copper ions
Cu
2+
(
aq
)
zinc ions
Zn
2+
(
aq
)
+
+
copper
Cu(
s
)
→
→
This is also a redox reaction involving the transfer
of two electrons from the zinc metal to the copper
ions. The zinc is oxidised to zinc ions in aqueous
solution, while the copper ions are reduced. (See
Chapter 5, p. 73, for a discussion of oxidation
and reduction in terms of electron transfer.) It is
possible to confi rm the reactivity series for metals
using competition reactions of the types discussed
in this section.
+
sodium
hydroxide
3NaOH(
aq
)
iron(
iii
)
hydroxide
Fe(OH)
3
(
s
)
+
sodium
chloride
3NaCl(
aq
)
→
+
+
→
