CHEMISTRY-CP
CHAPTER 10: THE MOLE
TEXTBOOK PAGES 310-345
OBJECTIVES:
 Define mole and describe its importance
 Identify and use Avogadro’s number
 Define atomic mass, formula mass and molar mass
 Calculate formula mass and molar mass
 Convert among the number of particles, mole and mass of a substance
 Define molar volume
 Convert between molar volume and moles
 Do multistep conversion problems
 Define and calculate percent composition
 Define and calculate molecular formulas
MOLES
× molar mass
× 22.4 L
÷ 22.4 L
÷molar mass
÷ (6.02 x 1023)
× (6.02 x 1023)
Mass (grams)
Atoms,
Molecules or
Formula Units
Volume (Liters)
Chemistry-CP
Chapter 10-The Mole
10-1 Chemical Measurements
 Mole:
The “mole” is a
counting unit—
just like a
“dozen” is a
counting unit
for 12.
o Establishes a relationship between:
o Sometimes referred to as:
Because:

When the substance is an element
1 mole =

When the substance is a molecular compound or diatomic element
1 mole =

When the substance is an ionic compound
1 mole =
The mass in grams of 1 mole of an element is numerically equal to the
___________________________ of that element.

Formula Mass:
Units =

Review of atomic mass
1) The mass of an atom
relative to the mass assigned
to carbon-12
2) Found on the periodic
table
3) Expressed in amu—
standard unit used to
describe the mass of an atom
Molar Mass:
4) Round to 2 decimals
Units =

Molar Mass =
Examples:
a) Find the formula mass of water.
b) Find the formula mass of acetic acid, HC2H3O2.
c) Find the formula mass of baking soda, NaHCO3.
d) What is the molar mass of glucose, C6H12O6?
e) Find the molar mass of carbon monoxide.
f) Find the molar mass of magnesium hydroxide.
g) Find the molar mass of hydrochloric acid.
10-2 Molar Conversions

Mole  Mass
o 1 mole = ___________________________________________
 The conversion factors are:

Moles  Particles
o 1 mole = ___________________________________________
 The conversion factors are:

Moles  Volume (for gases)
o Molar Volume:


Standard Temperature and Pressure (STP):
1 mole = ___________________________________________
o The conversion factors are:
Review: To Convert Between Units
1. Write down the measurement given in the question (number and unit)
2. Times a line.
3. Insert the correct conversion factor so that
a) units cancel
b) the unit you are converting to is on the top of the conversion factor
4. Check your answer to make sure the final unit is the desired unit. If not, continue with
the conversions by…
a) times a line again, and insert the appropriate conversion factor
Molar Conversion Factors:
1 mole = 6.02 × 1023 atoms, molecules or formula units
1 mole = molar mass (grams)
1 mole = 22.4 L (dm3)
Examples (1-step conversions)
a) How many molecules are in 2 moles of water?
Review of sig figs:
The answer to a
multiplication/division
problem should contain
the same # of sig figs as
the measurement with the
lowest # of sig figs.
b) You have an 11.2 g sample of table salt. How many moles of salt do you have?
c) A student fills a 5.0 L flask with carbon dioxide gas at standard temperature and pressure.
How many moles of gas are in the flask?
d) How many moles is equivalent to 16.3 grams of lithium bromide?
e) A piece of marble contains 8.74 × 1023 formula units of calcium carbonate. How many
moles of calcium carbonate is that?
Molar Conversion Factors:
1 mole = 6.02 × 1023 atoms, molecules or formula units
1 mole = molar mass (grams)
1 mole = 22.4 L (dm3)
More Examples (1-step conversions)
f) How many grams are present in a 2.50 mole sample of sodium carbonate?
g) Determine the number of atoms in 0.36 mol of aluminum.
h) How many liters of gas are present in 7.2 moles of chlorine gas?
Examples (Multi-step conversions)
a) How many grams of calcium are present in 7.2 × 1022 atoms of calcium?
b) You need 250 grams of table sugar, or sucrose (C12H22O11), to bake a cake. How many
sucrose molecules will be in the cake?
c) How many formula units of magnesium chloride are in 1.8 grams of magnesium
chloride?
d) If you burned 4.0 × 1024 molecules of natural gas, or methane (CH4), during a laboratory
experiment at STP, how many liters of methane did you burn?
10-3 Empirical and Molecular Formulas
 Percent Composition:
o Purpose of Calculating Percent Composition:
o To Calculate Percent Composition:
 Experimental Data:

Non-Experimental Data
Examples:
a) What is the percent composition of water?
b) A sample of unknown compound with a mass of 0.2370 g is extracted from the
roots of a plant. Decomposition of the sample produces 0.09480 g of carbon,
0.1264 g of oxygen and 0.0158 g of hydrogen. What is the percent
composition of the compound?
c) Find the percent composition of a compound that contains 2.30 g of sodium,
1.60 g of oxygen and 0.100 g of hydrogen in a 4.00 g sample of the compound.

Empirical Formula:

The empirical formula can be determined using:

To Determine an empirical formula:
Examples:
a) A compound was analyzed and found to contain 15.5 g Ca, 10.8 g O and
0.675 g H. What is the empirical formula of the compound?
b) Determine the empirical formula for a compound containing 2.128 g Cl
and 1.203 g Ca.
c) Determine the empirical formula for a compound containing 7.30 g Na,
5.08 g S and 7.62 g O.

Molecular Formula:
o The molecular formula is always:
o To Determine the Molecular Formula:
Examples:
a) Ribose is an important sugar that is found in DNA and RNA. Ribose has a molar
mass of 150 g/mol and a chemical composition of 40.0% carbon, 6.67% hydrogen
and 53.3% oxygen. What is the molecular formula for ribose?
b) Find the molecular formula for a compound that contains 4.90 g N and 11.2 g O. The
molar mass of the compound is 92.0 g/mol.
c) Beta-carotene, a compound found in carrots, can be broken down to form Vitamin A.
the empirical formula for beta-carotene is C5H7. The molar mass of beta-carotene is
536 g/mol. What is the molecular formula?