Unit 7: The Mole
(Chapter 10)
The Mole (Ch. 10)
I.
Chemical Measurements (10-1)
A. Atomic Mass & Formula Mass
1. The mass of atoms are so small (2.7 x 10^23 g) a relative mass scale was set up.
2. Based on the mass of carbon being 12
exactly.
3. The “made up” units to measure the mass of
atoms (atomic mass) are called: amu
4. Formula Mass: the sum of the atomic
masses of all the atoms in a compound
5. Examples- determine the atomic or formula
mass for the following (in amu’s):
a. Bromine (Br): ______
b. Gold (Au): ______
c. Sulfur Dioxide (SO2): ______
d. Carbonic Acid (H2CO3): ______
e. Acetic Acid (HC2H3O2): ______
f. Lead (II) Phosphate [Pb3(NO3)2]: _______
B. What is a Mole?
1. Since atoms are so small and we deal with so
many at a time, two things were developed:
a. Mole: the number of atoms of an element
equal to the number of elements in exactly
12.0 grams of carbon-12.
b. Avogadro’s Number: refers to the amount
of: 6.02 x 10^23 --> (of anything)
* Note – a mole of anything contains 6.02 x 10^23
C. Molar Mass
1. Molar Mass: the mass of 1 mole of anything
a. The number of items in a mole of substance is
the same, the mass varies.
b. The molar mass is equal to the atomic,
molecular, or formula mass.
2. Example – determine the molar mass for:
- Calcium Chloride (CaCl2): ________
- Glucose (C6H12O6): _________
II. Mole Conversions (10-2)
- See Example Problem Sheet
A. Moles to grams
1. Determine the molar mass
2. Use conversion: molar mass of X (g) = 1 mole
X; where X is anything
3. Examples
a. What is the mass of 2.5 moles of NaCl?
b. What is the mass of 3.75 moles of calcium
hydroxide?
B. Grams to moles
1. Determine the molar mass
2. Use conversion: molar mass of X (g) = 1
mole; where X is anything
3. Examples:
a. How many moles of carbon are in a
sample with the mass of 24 grams?
b. How many moles of NaNO3 are in 7.57
grams of sample?
C. Moles to number of units
1. Use conversion: 1 mole = 6.02 x 10^23
units
2. Examples:
a. How many molecules are in a 2-mole
sample of C?
b. How many molecules are in a sample of
.0891 moles of NaNO3?
D. Number of units to moles
1. Use conversion: 1 mole = 6.02 x 10^23
units
2. Examples:
a. How many moles of NaOH are in a
sample with 2.76 x 10^23 molecules
of NaOH?
E. Grams to number of units
1. Determine molar mass
2. Convert grams to moles
3. Convert moles to units
4. Examples:
a. How many molecules of NaNO3 are in a
sample of 7.57 grams of NaNO3?
b. How many molecules are in a sample of
oxygen (O2) gas with a mass of 64 grams?
F. Number of units to grams
1. Determine molar mass
2. Convert units to moles
3. Convert moles to grams
4. Examples:
a. How many grams of NaOH are in a
sample with 2.76 x 10^23 molecules?
b. How many grams of NaCl are in a
sample with 4.56 x 10 ^24 molecules?