This document provides information about moles, molar mass, and stoichiometry calculations. It defines a mole as the amount of substance containing 6.02 x 1023 particles and molar mass as the mass of one mole of a substance. Formulas are given for calculating molar mass from elemental compositions and for converting between mass and moles using molar mass. Examples show calculations of molar mass for compounds and conversions between grams and moles for different substances.

1. 2.8 – To explain the electrolytic
property of a solute using ion
dissociation
3.3 – To associate the concept of
the mole with the measurement of
quantity of matter
3.5 – To associate the concept of
the mole with a measure of the
molar mass of a substance
436MOLES

2. IMPORTANT INFORMATION:
- free ions must be present to allow
conductivity
- conductivity depends on the number of
ions present
- substances that conduct electricity are
considered electrolytes
- substances that do not conduct electricity
are considered nonelectrolytes
ACIDS
SALTS
- all ionize allowing the conductance
of electricity
- some ionize more readily then others
resulting in strong or weak electrolytes
BASES

3. The mass of a mole of any element or
compound is called its molar mass.
A Mole is the amount of substance that
contains 6.02 x 1023 (Avogadro’s #)
particles of that substance
mass of a substance (g)
molar mass of substance (g/mol)

4. TO FIND MOLAR
MASS OF
SUBSTANCE
add up the molar masses
of the elements shown
in the formula
1. H2O (water)
Hydrogen = 1.0g/mol x 2
Oxygen = 16 g/mol x 1
Molar Mass = 18 g/mol
2. KNO3 (potassium nitrate)
Potassium (K)= 39.1g/mol x 1
Nitrogen (N) = 14 g/mol x 1
Oxygen (O) = 16g/mol x 3
Molar mass = 101.1 g/mol
THEREFORE: 1 mole of water has a molar mass of 18g/mol and 1
mole of potassium nitrate has a molar mass of 101.1g/mol.

5. What is the molar mass of (NH4)2SO4
What is the molar mass of NaCl?
Na = 1 x 23g/mol = 23
Cl = 1 x 35.5 g/mol = 35.5
58.5 g/mol
N = 2 x 14 g/mol = 28
H = 8 x 1 g/mol = 8
S = 1 x 32 g/mol = 32
O = 4 x 16 g/mol = 64
132 g/mol

6. mass of a substance (g)
molar mass of substance (g/mol)
convert

7. How many moles of hydrochloric acid
are in 100 grams of hydrochloric acid
(HCl)?
n = ?
g = 100
Molar Mass = 36.5g/mol
n = 100 g
36.5g/mol
n = 2.74 mol
n (# of moles)= grams
molar mass
Hydrogen 1g/mol x 1
Chlorine 35.5 g/mol x 1
molar mass = 36.5 g/mol

8. How many grams are in 11.1
moles of water (H20)?
n = 11.1 moles
g =
Molar Mass = 18 g/mol
11.1 = _____
18 g/mol
g = 200 grams
n (# of moles)= grams
molar mass
Hydrogen 1 g/mol x 2
Oxygen 16 g/mol x 1
molar mass = 18 g/mol

9. What is the mass of 0.42
moles of potassium nitrate
(KNO3)?
n(moles) = 0.42 moles
Molar Mass = 101.1 g/mole
g = ?
n (# of moles)= grams
molar mass
K = 39.1 g/mole
N = 14 g/mole
0 = 16 x 3 = 48g/mole
101.1 g/mole
0.42 = __g__
101.1
g = 42.46 grams

10. o The mass of a mole of any element or compound is called
its molar mass.
o A Mole is the amount of substance that contains
6.02 x 1023 (Avogadro’s #) particles of that substance
o Formula to convert between moles and mass (g) is:
1. H2O (water)
Hydrogen = 1.0g/mol x 2
Oxygen = 16 g/mol x 1
Molar Mass = 18 g/mol
n (# of moles)= grams
molar mass

11.  Study guide, Module 3, page 11 and
18
 436 WORKSHEET # 2