REACTIONS IN
SOLUTION
Section 5.5
PROBLEM:
PROBLEM: Dissolve
Dissolve 5.00
5.00 gg of
of NiCl
NiCl22•6
•6 H
H22O
O in
in
enough
enough water
waterto
tomake
make250
250 mL
mL of
of solution.
solution.
Calculate
molarity
Calculate molarity.
molarity..
Terminology
Terminology
In solution we need to define
the • SOLVENT
the component whose
physical state is
preserved when
solution forms
• SOLUTE
the other solution
component
The
The Nature
Nature of
of the
the KMnO
KMnO44 Solution
Solution
Step 2: Calculate molarity
[NiCl
NiCl2•6 H2O ] = 0.0841 M
Molarity(M) =
moles solute
liters of solution
The
The Nature
Nature of
of aa Na
Na22CO
CO33 Solution
Solution
3 Na 2CO3
1 mol
= 0.0210 mol
237.7 g
0.0210 mol
= 0.0841 M
0.250 L
The amount of solute in a solution
is given by its concentration.
This water-soluble compound is ionic
Na2CO3(aq)
aq) --> 2 Na+(aq)
aq) + CO32-(aq)
aq)
Step 1: Calculate moles
of NiCl2•6H2O
5.00 g •
Concentration
Concentration of
of Solute
Solute
KMnO4(aq)
aq) --> K+(aq)
aq) + MnO4-(aq)
aq)
If [KMnO4 ] = 0.30 M, then
[K+] = [MnO 4-] = 0.30 M
Page 1
If [Na2CO3] = 0.100 M, then
[Na+] = 0.200 M
[CO32-] = 0.100 M
USING
USING MOLARITY
MOLARITY
USING
USING MOLARITY
MOLARITY
What mass of oxalic acid, H 2C2O4, is
required to make 250. mL of a
0.0500 M solution?
Because
Conc (M) = moles/volume = mol/V
mol/V
this means that
moles = M • V
What mass of oxalic acid, H2C2O4, is
required to make 250. mL of a 0.0500 M
solution?
moles = M • V
Step 1: Calculate moles of acid
required.
(0.0500 mol/L)(0.250
mol/L)(0.250 L) = 0.0125 mol
Step 2: Calculate mass of acid
required.
(0.0125 mol )(90.00 g/mol
g/mol)) =
PROBLEM:
PROBLEM: You
You have
have 50.0
50.0 mL
mL of
of 3.0
3.0 M
M
NaOH
NaOH
NaOH and
and you
you want
want 0.50
0.50 M
M NaOH.
NaOH.. What
What
do
you
do?
do you do?
Add water to the 3.0 M solution to lower
its concentration to 0.50 M
Dilute the solution!
1.13 g
PROBLEM:
PROBLEM: You
You have
have 50.0
50.0 mL
mL of
of 3.0
3.0 M
M
NaOH
NaOH
NaOH and
and you
you want
want 0.50
0.50 M
M NaOH.
NaOH.. What
What
do
you
do?
do you do?
H2O
But how much water
do we add?
Preparing
Preparing Solutions
Solutions
• Weigh out a solid
solute and dissolve
in a given quantity
of solvent.
• Dilute a
concentrated
solution to give one
that is less
concentrated.
PROBLEM:
PROBLEM: You
You have
have 50.0
50.0 mL
mL of
of 3.0
3.0 M
M
NaOH
NaOH
NaOH and
and you
you want
want 0.50
0.50 M
M NaOH.
NaOH.. What
What
do
you
do?
do you do?
How much water is added?
The important point is that --->
moles of NaOH in ORIGINAL solution =
moles of NaOH in FINAL solution
3.0 M NaOH
Concentrated
0.50 M NaOH
Dilute
Page 2
PROBLEM:
PROBLEM: You
You have
have 50.0
50.0 mL
mL of
of 3.0
3.0 M
M
NaOH
NaOH
NaOH and
and you
you want
want 0.50
0.50 M
M NaOH.
NaOH.. What
What
do
do you
you do?
do?
PROBLEM:
PROBLEM: You
You have
have 50.0
50.0 mL
mL of
of 3.0
3.0 M
M
NaOH
NaOH
NaOH and
and you
you want
want 0.50
0.50 M
M NaOH.
NaOH.. What
What
do
do you
you do?
do?
Moles of NaOH in original solution =
M•V
=
Conclusion:
H2O
add 250 mL
of water to
(3.0 mol/L)(0.050
mol/L)(0.050 L) = 0.15 mol NaOH
Therefore, moles of NaOH in final
solution must also = 0.15 mol NaOH
(0.15 mol NaOH)(1
NaOH)(1 L/0.50 mol)
mol) = 0.30 L
or 300 mL = volume of final solution
Preparing
Preparing Solutions
Solutions
by
by Dilution
Dilution
3.0 M NaOH
Concentrated
50.0 mL of
3.0 M NaOH
to make 300
mL of 0.50 M
0.50 M NaOH
NaOH.
NaOH.
Dilute
Page 3
A shortcut
Minitial • Vinitial = Mfinal • Vfinal