Moles and Solutions
Counting Units
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Pair
Trio
Quartet
6-pack
Dozen
Baker’s dozen
Score
Gross
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2
3
4
6
12
13
20
144
Titan Lab

Created a counting unit for convenience.

This is a similar process to what we do for
molecules
Molecules are very small
 Need a very big counting unit

Titan Lab

How can we figure out how many
Cheerios are in a box without counting
them?
Counting Large Numbers

How long would it take to count to 1 million
if you counted one number each second?
Counting Large Numbers

How long would it take to count to 1 billion
if you counted one number each second?
Counting Unit for Molecules
The mole
 Abbreviated mol
 Defined in terms of two different units


Masses of atoms
 Measured

in amu
Masses of things that are convenient to
measure
 Measured
in grams
Moles
Define the mole in a similar way to the
titan
 The mass of 1 atom in amu is equal
numerically to the mass of 1 mole of
atoms in grams.
 Where 1 amu = 1.66054 x 10-27 kg

Moles
How many things are in one mole?
 Exact same process as Titan lab

Moles

1 mol is 6.022 x 1023 items.

1 mol of doughnuts is?


1 mol of quizzes?


6.022 x 1023 doughnuts
6.022 x 1023 quizzes
1 mol of dollar bills?

6.022 x 1023 dollar bills
Moles are Huge Counting Units

How many years would it take to spend
1mol of dollar bills?

Assume you could spend $1 million every
second of your life
Moles are Huge Counting Units

Could 1 mol of basketballs cover the
Earth?

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How big would 1 mol of grapefruits be?

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About the size of the Earth
How many human cells are on Earth?


With a depth of 50 miles
About 1 mole of human cells
How many moles of sand grains are in the
Sahara desert?

About 2 moles of sand grains
Moles Are Huge Counting Units

What is the volume of 1 mol of water
molecules?


18.01mL
Moles are huge counting units because
molecules are so tiny.
How do we count moles?

Remember how we determined the
number of things in a mole…
Consider carbon
 The average mass of 1 carbon atom is?



12.01amu
The mass of 1 mole of carbon atoms is?

12.01g
Conversion Factors

Molar mass – the mass of 1 mole of atoms
in grams
Found on periodic table
 Numbers on periodic table are

 The
average mass of 1 atom in amu
 The mass of 1 mole of atoms in grams


Mass on periodic table in grams = 1 mol
Avogadro’s number – 6.022x1023 things
Found on reference table
 1 mol = 6.022x1023 things

Practice Problems

How many carbon atoms are in 5.10 mol
of carbon?

What is the mass of 5.10 mol of carbon?
Practice Problems

What is the mass of 2.50mol of water?

How many water molecules are in 2.50mol
of water?
Practice Problems

What is the mass of 1.89x1024 molecules of
ammonia?

How many formula units of calcium chloride
are in 18.5g of calcium chloride?
Solutions
Solutions



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Solution – a homogeneous mixture of two or
more compounds.
Homogeneous – looks the same throughout,
mixed at the molecular level
Solvent – the compound that is the majority of a
solution, the compound that is doing the
dissolving
Solute – the compound that there is less of in a
solution, what got dissolved in the solvent.


Can be more than one solute in a solution
Can only be one solvent
Different Solutions

Solid Dissolved in a Liquid
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Liquid Dissolved in a Liquid

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An unopened Pepsi
Gas Dissolved in a Gas
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Rubbing Alcohol (isopropanol in water)
Gas Dissolved in a Liquid

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Salt Water
Air
Solid Dissolved in a Solid

Alloys
Concentration


Need to be able to tell how much compound
is dissolved in a solution.
Molarity – M – moles of solute per liter of
solution
mol of solute
M
L of solution

In equations, a molarity of a specific
substance maybe represented using square
brackets

Ex. [NH3] = 0.100M
Practice Problems

What is the molarity of a solution made by
dissolving 0.125mol of sodium hydroxide
in enough water to make 500.0mL of
solution?
Practice Problems

What volume of 18.0M sulfuric acid is
required to obtain 0.0500mol sulfuric acid?
Practice Problems

How many moles of iron(II) sulfate are in
125mL of a [FeSO4] = 0.0530M solution?
Practice Problems

15.5g of barium chloride is dissolved in
enough water to make 150mL of solution.
What is the concentration of barium
chloride?
Practice Problems

What volume in L of a 0.100M ammonia
solution contains 4.95x1023 ammonia
molecules?
Practice Problems

What mass of glucose is dissolved in
2.00L of a [C6H12O6]=0.05M solution?
Practice Problems

What volume in L of a 0.100M ammonia
solution contains 4.95x1023 ammonia
molecules?

What mass of glucose is dissolved in
2.00L of a [C6H12O6]=0.05M solution?
Practice Problems

What volume of a 0.150M solution of
aluminum nitrate is required to obtain
5.00g of aluminum nitrate?

How many formula units of titanium(IV)
oxide are in 10.0g of titanium(IV) oxide?
Solubility
Electrolytes
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What type of compounds are electrolytes?
Why are ionic compounds electrolytes?
Consider sodium chloride:

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Consider sucrose (sugar, C12H22O11):
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Is this an electrolyte?
Why?
Is this an electrolyte?
Why?
Consider calcium carbonate:
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Is this an electrolyte?
Why?
Electrolytes

Why is calcium carbonate NOT an
electrolyte?
Not all ionic compounds are soluble in
water.
 In some compounds the attractions
between the ions is too great to allow them
to be separated.

Solubility Rules

Located in your reference table
A compound that is soluble will dissolve in water
 A compound that is insoluble will “not” dissolve in
water


Solubility is really a sliding scale
Notice the solubility rules have a cutoff of 0.1M
 Anything that can produce a solution of 0.1M or
greater is soluble
 Anything that cannot produce a solution of 0.1M
is “insoluble.”

Practice
Are the following soluble or insoluble in
water?
 Sodium iodide
 Iron(III) carbonate
 Silver sulfate
 Calcium sulfide
 Potassium phosphate
Solubility Curve

Remember everything has a different
solubility in water.

Some things are hardly soluble at all

“Insoluble”

Some things are much more soluble

This is shown with a solubility curve

Shows the maximum amount of solute that
can dissolve
Trends in Solubility

Most solids are more soluble as
temperature increases

Most gasses are more soluble as
temperature decreases.

Gas solubility can be increased by adding
pressure to a liquid.
How do we describe solutions?

Concentrated – has lots of solute
dissolved in it

Dilute – doesn’t have a lot of solute
dissolved in it.
How do we describe solutions?

Saturated solution – a solution that can
NOT dissolve more solute.


At capacity
Unsaturated solution – a solution that can
dissolve more solute.

Not yet at capacity
What the heck is “Supersaturated?”

Supersaturated solution – when a solution
has more solute dissolved than it should
Over capacity
 NOT stable


Nucleation site – some imperfection that
allows the excess solute in a solution to
leave the solution
Mentos in Diet Coke
 http://www.eepybird.com/

How is a supersaturated solution
made?
Initially make a traditional saturated or
unsaturated solution
 Change the conditions on the solution so
that it is then supersaturated.

Dissolve lots of solute in hot water and then
cool the hot water.
 Dissolve carbon dioxide at high pressure and
then release the pressure.

Dilution
A Real World Problem

I need 500.0mL of 1.0M hydrochloric acid.

I only have 12.0M hydrochloric acid…

How do I make the solution that I need?

Take some of the 12.0M HCl and dilute it
out with water.
How much do I dilute?

How many moles of HCl need to be
dissolved in the dilute solution?
m oldilute
M dilute 
Ldilute
m oldilute  M diluteLdilute
 Where are these moles of HCl going to
come from?
moldilute  molconc
How much do I dilute?

What volume of concentrated solution do I
need to get that number of moles?
m olconc
M conc 
Lconc
Lconc
m olconc

M conc
Combine it all together
Lconc
m olconc

M conc
Since, m olconc  m oldilute
And m oldilute  M dilute Ldilute
Lconc
M dilute Ldilute

M conc
Rearranging we get
M conc Lconc  M dilute Ldilute
Or
M 1V1  M 2V2
Practice Problems

What volume of 12.0M HCl is needed to
make 500.0mL of a 1.0M HCl solution?
Practice Problems

I have roughly 750mL of 12.0M HCl left for
the year. How much 6.0M HCl can I
make?
Practice Problems

What is the concentration of a solution
prepared by mixing 10.0mL of 18.0M
H2SO4 in enough water to make 0.5000L
of solution?
Practice Problems

A solution of iron(III) nitrate is prepared by
taking 5.0mL of a stock solution of unknown
concentration and diluting it to 2.00L. This
solution is later found to have a
concentration of 0.0112M. What is the
concentration of the unknown stock solution?
Practice Problems

I found an unlabeled solution of nitric acid in my
acid cabinet when I came to West. I took
10.0mL of the unknown solution and diluted it to
1.00L. I then titrated that solution and
determined its concentration to be 0.065M.
What is the concentration of the unlabeled
solution?
Counting Atoms
Practice Problem

How many hydrogen atoms are in
5.50x1023 water molecules?
Practice Problems

What mass of carbon dioxide is needed to
obtain 4.50x1022 atoms of oxygen?
Practice Problems

How many sulfur atoms are found in 3.55g
of iron(III) sulfide?
Practice Problems

What volume (in mL) of 0.34M sucrose
solution (C12H22O11) contains 1.50x1023
carbon atoms?
Practice Problems
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How many mL of 0.525M calcium chloride are
needed to obtain 5.00x1022 chloride ions?
What is the molarity of a solution prepared by
dissolving 36.05g of sodium hydroxide in 3.00L
of water?
What is the mass of ammonia dissolved in
100.0mL of a 14.8M ammonia solution?
What mass of aspirin (C9H8O4) contains
1.00x1023 atoms of oxygen?
What is the [HCl] of a solution prepared by
dissolving 15.0mL of 12.0M hydrochloric acid in
enough water to make 0.50L of solution?

How many sodium ions are dissolved in
5.00mL of a 0.100M sodium sulfate
solution?