Unit V: The Mole Concept
V.6. Molar Concentrations
Solution

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A Homogeneous mixture
A mixture that looks like a pure substance.
Particles of all substances are completely
mixed together
Solutions: Homogenous
Mixtures

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A solute is the
substance to be
dissolved (*component
present in smaller
amounts)
The solvent is the one
doing the dissolving
(*component present in
larger amounts)
Universal solventgenerally thought of as
water
Concentration

The CONCENTRATION of a substance in
solution is the amount of the substance which
exists in a given volume of solution

In Simple Terms
am ount of  solute
Concentration 
volum e of  solution
Concentration
More Terms


Concentrated solution – there is a large
amount of substance dissolved in the solution
A Dilute solution – there is very little
substance dissolved in the solution
Concentration

ppm
Units of Concentration:
g
L
g
mL
mg
L
mg
mL
Molar Concentration
Molarity


Unit mainly used in chemistry
Molarity is the number of moles of the
substance contained in 1L of solution
m oles of  solute
Molarity 
litres  of  solution
Molarity
mol
M
L
mol
L
M
mol  M  L
mol
M
L
Molarity
mol
M
L
Molarity

If we can calculate moles then we can
determine grams using our Mole Diagram
grams
mol
M
L
CHEM LINGO

[ Square Brackets
Concentration

[NaOH]
] = Molarity or Molar
Example 1
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Austin dissolves 40.0 g of NaOH in enough water to
make a 200.0 mL solution. What is the molar
concentration of NaOH?
[NaOH] = ? M
Plan grams  moles  Molarity
Example 1



Austin dissolves 40.0 g of NaOH in enough water to
make a 200.0 mL solution. What is the molar
concentration of NaOH?
[NaOH] = ? M
Plan grams  moles  Molarity
Example 2
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Angela wants to make a 600.0 mL of 0.60 M CaCl2.
What mass of solid CaCl2 should she start with?
Plan: M x L  mol g
Example 2


Angela wants to make a 600.0 mL of 0.60 M CaCl2.
What mass of solid CaCl2 should she start with?
Plan: M x L  mol g
Example 3
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Chris wants to evaporate some 3.0M NaCl to obtain
26.325 g of NaCl. What volume of solution should she
evaporate?
g  mol  L
Example 3

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Chris wants to evaporate some 3.0M NaCl to obtain
26.325 g of NaCl. What volume of solution should he
evaporate?
g  mol  L
Example 4
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Elyse has 4.0 g of NaOH and she wants to make a 0.80
M solution. She should add water to a total volume of
what?
Plan: g  mol  L
Example 4

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Elyse has 4.0 g of NaOH and she wants to make a 0.80
M solution. She should add water to a total volume of
what?
Plan: g  mol  L
Experimental Procedure
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Give directions in a step wise manner
Rough outline of experimental procedure
Typically want you to figure out the mass or
volume required to make a certain solution
Experiment Procedure
Example 1
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Blair needs to make 300.0 mL of 0.25 M NaOH.
Describe the procedure Blair needs to follow in order to
make this solution.
Plan: M x L  mol  g
Experiment Procedure
Example 1


Blair needs to make 300.0 mL of 0.25 M NaOH.
Describe the procedure Blair needs to follow in order to
make this solution.
Plan: M x L  mol  g
Experiment Procedure
Example 1


Blair needs to make 300.0 mL of 0.25 M NaOH.
Describe the procedure Blair needs to follow in order to
make this solution.
Plan: M x L  mol  g
Experimental Procedure
Example 2
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Mark is asked to give directions to make 250.0 mL of
0.55M K2SO4. What should he say?
M x L  mol  g
Experimental Procedure
Example 2

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Mark is asked to give directions to make 250.0 mL of
0.55M K2SO4. What should he say?
M x L  mol  g
Experimental Procedure
Example 2


Mark is asked to give directions to make 250.0 mL of
0.55M K2SO4. What should he say?
M x L  mol  g
Experimental Procedure
Example 3
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Tianna needs to tell Savannah how to make a 2.00L
solution of 6.0 M NaOH.
Plan: M x L  mol  g
Experimental Procedure
Example 3
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Tianna needs to tell Savannah how to make a 2.00L
solution of 6.0 M NaOH.
Plan: M x L  mol  g
Experimental Procedure
Example 3
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Tianna needs to tell Savannah how to make a 2.00L
solution of 6.0 M NaOH.
Plan: M x L  mol  g
Hebden

Do Exercises 59(b, d, e & f), 60 (c & e), 62 and 64 on
pages 98 of Hebden
Dilutions of Solution

Concentration and Volume are inversely
related
am ount of  solute
Concentration 
volum e of  solution
1
Concentration 
volum e of  solution
Dilutions of Solution

When we add water the volume increases

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Volume ↑ Concentration ↓
When we remove water the volume
decreases

Volume ↓ Concentration ↑
Dilutions of Solutions

For the same solution


If we double the volume  the concentration is
halved (x ½)
If we triple the volume  the concentration x 1/3
Dilutions of Solutions
Volume
Concentration
CxV
Concentration
Concentrat ion  volume  constant
Concentrat ion  volume  k
50.0 mL of
6.0 M HCl
100.00 mL of
0.30 M HCl
Add 50.0 mL
of water
FIND BEAKER
Concentration
Concentrat ion  volume  k
Initial Concentrat ion  Initial volume  Final Concentrat ion  Final volume
IC IV  FC  FV
Dilution Formula
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I = Initial
F = Final
V = Volume
C = Concentration
IC IV  FC  FV
Dilution Formula
IV
FC  IC 
FV
Example

Matt adds 150.0 mL of water to 50.0 mL of 0.60 M
solution of HCl. Find the final [HCl] .
FC  IC 
IV
FV
Example 2

Connor adds water to 100.0 mL of 0.25 M HF to a
volume of 400.0 mL Find the final [HF].
FC  IC 
IV
FV
Example 3*

Tanner dilutes 60.0 mL of 0.40 M HNO3 to 0.15 M. What
is the final volume?
Example 3*

Tanner dilutes 60.0 mL of 0.40 M HNO3 to 0.15 M. How
much water did Tanner add?
Diluting Stock Solutions

Stock solutions – are concentrated
solutions from the suppliers
Diluting Stock Solutions
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12 M HCl
15 M HNO3
18 M H2SO4
Example 4

Natasha wants to make 100.0 mL of 0.20 M HCl. What
volume of 12.0 M HCl should she start with?
Example 4

Natasha is unfamiliar with the ways of chemistry. Explain
how she should proceed to make her solution from the
concentrated stock solution.
Hebden
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Do Exercises 78, 82, 89, 91 on pages 102-103 of
Hebden
Do Hand-In Assignment #10
DONE WITH THE MOLE
Unit Test
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% mass and % composition
Mass of element when given a mass of a
compound
Empirical and Molecular Formulas
Concentration: Solution, Solvent, Solute
Molar concentration/ Molarity
Dilutions of Solutions