What is the concentration of cl- ions in a 0.1 m solution of calcium chloride?
Answers
Explanation:
molarity is defined as the number of moles of solute present in
1 L
of solution. For the first solution, you have aluminium chloride,
AlCl
3
, as the solute and a volume of
10
cm
3
⋅
1 dm
3
10
3
cm
3
=
10
−
2
.
dm
3
This means that the first solution will contain
10
−
2
dm
3
⋅
3.3
⋅
10
−
2
.
moles AlCl
3
1
dm
3
=
3.3
⋅
10
−
4
.
moles AlCl
3
Now, every mole of aluminium chloride that dissociates in aqueous solution produces
one mole of aluminium cations,
1
×
Al
3
+
three moles of chloride anions,
3
×
Cl
−
This means that for every
1
mole of aluminium chloride dissolved to make this solution, you will end up with
3.3
⋅
10
−
2
moles AlCl
3
⋅
3 moles Cl
−
1
mole AlCl
3
=
9.9
⋅
10
−
4
.
moles Cl
−
Now do the same for the calcium chloride solution. You will have
20
cm
3
⋅
1 dm
3
10
3
cm
3
=
2.0
⋅
10
−
2
.
dm
3
This means that the solution contains
2.0
⋅
10
−
2
dm
3
⋅
5.0
⋅
10
−
2
.
moles CaCl
2
1
dm
3
=
1.0
⋅
10
−
3
.
moles CaCl
2
Now, every mole of calcium chloride that dissociates in aqueous solution will produce
one mole of calcium actions,
1
×
Ca
2
+
two moles of chloride anions,
2
×
Cl
−
This means that the second solution will contain
1.0
⋅
10
−
3
moles CaCl
2
⋅
2 moles Cl
−
1
mole CaCl
2
=
2.0
⋅
10
−
3
.
moles Cl
−
Therefore, you can say the solution B) will contain the higher concentration of chloride anions, since
2.0
⋅
10
−
3
.
moles Cl
−
>
9.9
⋅
10
−
4
.
moles Cl
−
Use the same approach to calculate the number of moles of chloride anions present in solutions C) and D) and compare all four solutions to find the answer.