(4.4) Calculations Involving the
MOLE
moles # of particles
moles  mass
• Molar Mass (M)
• Avogadro’s number (NA)
• Mole (n)
By the end of the lesson you will be able to....
 convert mass to moles and vice versa
 convert moles to number of particles and
vice versa
 convert mass to number of particles and
vice versa
• dimensional analysis is utilized in many
subjects.
• to measure distances, we convert between
meters and kilometers
• to follow recipes, we convert between cups
and tablespoons
• the conversion factors utilized in chemistry
are specific to the language of chemistry
• when substances react, they do so in simple
ratios of moles. However, in the lab,
balances give readings in grams
• this is one of the many reasons why we
need to understand how to convert grams to
moles and moles to grams
Aluminum is often used for the structure of
light-weight bicycle frames. How many
grams of Al are in 3.00 moles of Al?
3.00 moles Al
? g Al
(to convert between mass and moles or vice
versa, you need the molar mass)
1. Molar mass of Al
1 mole Al = 27.0 g Al
2. Conversion factors for Al
27.0g Al
1 mol Al
or
1 mol Al
27.0 g Al
3. Setup m = 3.00 moles Al
Answer
x
27.0 g Al
1 mole Al
m = 81.0 g Al
The artificial sweetener aspartame (Nutra-Sweet),
formula C14H18N2O5, is used to sweeten diet foods,
coffee and soft drinks. How many moles of aspartame
are present in 225 g of aspartame?
1. Molar mass of aspartame
M =
(14)(12.01g/mol) + (18)(1.01g/mol) + (2)
(14.01g/mol) + (5)(16.00g/mol)
=
294.34g/mol
2. Conversion factors for aspartame
294.34 g aspartame
1 mol aspartame
or
1 mol aspartame
294.34 g aspartame
The artificial sweetener aspartame (Nutra-Sweet),
formula C14H18N2O5, is used to sweeten diet foods,
coffee and soft drinks. How many moles of aspartame
are present in 225 g of aspartame?
3. Setup
n = 225 g aspartame x
1 mol aspartame
294.34 g aspartame
Answer
n = 0.764 mol aspartame
moles (n) =
mass (m)
molar mass (M)
mass(m) = moles(n) x molar mass (M)
How many molecules are in 3.50 mol of table
sugar, sucrose?
1. Avogadro’s #
NA = 6.02 X 1023 molecules/mol
2. Conversion factors
6.02 X 1023 molecules
or
6.02 X 1023 molecules
1 mol
3. Setup
N = 3.50 mol sugar
Answer
1 mol
x 6.02 X 1023 molecules
1 mol sugar
N = 2.11 X 1024 molecules of sugar
How many molecules are present in 2.0 mol of
carbon dioxide? How many atoms are present?
N
= 2.0 mol X 6.02 X 1023 molecules
mol
= 1.2 X 1024 molecules CO2
# of atoms = # of molecules X # of atoms
molecule
= 1.2 X 1024 molecules CO2 X 3 atoms
1 molecule
CO2
= 3.6 X 1024 atoms
How many moles are in 2.40 X 1023 formula
units of table salt, NaCl?
1. Avogadro’s #
NA = 6.02 X 1023 formula units/mol
2. Conversion factors
6.02 X 1023 formula units
1 mol
or
6.02 X 1023 formula units
3. Setup n = 2.40 X 1023 form. units x
Answer
1 mol
1 mol
6.02 X 1023 form. units
n = 0.399 mol NaCl
moles (n) = # of particles (N)
Avogadro’s # (NA)
# of particles (N) = moles(n) x Avogadro’s # (NA)
What is the mass (in grams) of 1.20 X 1024
molecules of glucose (C6H12O6)?
1. Calculate the moles
n =
1.20 X 1024 molecules X
=
1 mol
6.02 X 1023 molecules
1.99 mol
2. Calculate the molar mass of glucose
M = (6)(12.01) + (12)(1.01) + (6)(16.00) g/mol
= 180.18 g/mol
What is the mass (in grams) of 1.20 X 1024
molecules of glucose (C6H12O6)?
3. Calculate the mass of glucose
m = 1.99 mol
= 3.59 X 102 g
X
180.18 g
1 mol
A Summary
molar mass
mass (g)
Avogadro’s number
moles (mol)
# particles
Everything must go through
Moles!!!
NOW IT’S YOUR TURN!!
• TRY SOME PROBLEMS USING THE STEPS
SHOWN HERE.
• THE MORE YOU DO THE EASIER THEY
GET!!!!