Nielsen
Bhaskar/PC/1713K/A
2/05
1
CHM1041
Answer to Exercise set # 7
Ionic Equilibria I
1.
By choosing the proper temperatures, both
(normally a solid) and
(normally
a gas) are liquids.
But liquid
is a good conductor of electricity and liquid
is
not.
Why is this?
On the other hand, a water solution of either substance at room
temperature is a good conductor.
Explain why.
NaC1
HC1
NaC1
HC1
NaC1
is an ionic solid at room temperature and incapable of conducting electricity as a
solid.
Mobile ions are required for the conduction of electric current, and the ions of
solid
are locked in the crystal lattice.
As a liquid at higher temperatures (molten
state), the ions become mobile and the conduction of current is possible.
Hydrogen
chloride,
is a polar covalent molecule and cannot conduct electric current as a
solid, pure liquid, or gas.
In water solution, however, both
and
produce
100% ions and both conduct current.
NaC1
HC1,
NaC1
HC1
100%
(
)
(
)
(
)
2
H O
s
+1
-1
aq
NaC1
Na
+
C1
aq
⎯⎯⎯→
(
)
(
)
(
)
2
3
+1
-1
2
g
a
H O
HC1
+ H O
H O
C1
⎯⎯⎯→
+
q
aq
100%
2.
Calculate the concentration of each of the ions in the following solutions of strong
electrolytes:
(a)
0.0090 M HBr
(
)
(
)
2
H O
+1
1
ag
HBr
H
Br
ag
−
⎯⎯⎯→
+
100%
0.0090 M
0.0090 M
(b)
2
4
0.0102 M Li SO
100%
( )
(
)
(
)
2
2
H O
4
s
+1
-2
4
ag
ag
Li SO
SO
2 Li
+
⎯⎯⎯→
0.0090 M
0.0102 M
(c)
(
)
(
)
2
4
6
3
2
0.0033 M
A1 H O
SO
⎡
⎤
⎣
⎦
(
)
(
)
( )
(
)
(
)
2
H O
2
+3
-2
2
4
6
3 s
6 ag
2
A
H O
SO
2 A
H O
+ 3 SO
⎡
⎤
⎯⎯⎯→
⎣
⎦
A
A
4
0.0066 M
0.0099 M
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