Aim: What is the Mole?
Do Now: Answer should be in the correct number of significant figures.
1. 4.9 × 102 + 7.9 × 103
3. (1.247 × 10–3) ÷ (2.9 × 10–2)
2. 4.9 × 10-6 - 7.9 × 10-5
4. (2.6 × 105) (9.2 × 10–13)
Counting large numbers…
• Easier when you use counting units:
Dozen
Ream
Pair
Gross
• Regardless of the object, the number that the
units represents is always the same
• Atoms and molecules are extremely small,
making it impossible actually count them (even in
the smallest of samples)
• Chemists need a unit for counting accurately the
# of atoms, molecules, or formula units; they use
the mole
• Mole (mol) = the SI base unit used to measure
the amount of a substance
• 1 mole of anything contains 6.02 x 1023
representative particles
1 mole of apples =
6.02 x 1023 apples
1 mole of diamonds =
6.02 x 1023 diamonds
1 mole of baseballs =
6.02 x 1023 baseballs
1 mole of carbon atoms =
6.02 x 1023 carbon atoms
The same applies to moles of compounds
• How many molecules are in 1 mol NH3?
6.02 x 1023 NH3 molecules
• How many molecules are in 1 mol C9H8O4?
6.02 x 1023 C9H8O4 molecules
What is Avogadro’s Number
• 6.02 X 1023 representative particles/mol
• 1 mol of any substance has 6.02 X 1023 representative
particles
What are representative particles?
• Representative particles refers to the species present
in a substance: usually atoms, molecules, or formula
units
Converting Particles to Moles
• How many roses are in 3 ½ dozen?
USE CONVERSION FACTORS!!!
3.5 dozen x 12 roses =42 roses
1 dozen
• How many pencils are in 6 gross?
6 gross x 144 pencils =864 pencils
1 gross
conversion factor
conversion factor
Conversion factor
• A conversion factor is used to convert a
measured quantity to a different unit of
measure without changing the relative amount.
To accomplish this, a ratio (fraction) is
established that equals one (1)
Converting Number of Particles to Mole
Conversion factor
Converting number of atoms to moles
Units you want are on
top
0.465
These units cancel out
Converting Moles to Particles and Particles to
Moles
• How many moles contain 4.50 x 1024 atoms of zinc?
4.50 x 1024 atoms Zn x 1 mol zinc
6.02 x 1023 atoms Zn
7.48 mol Zn
Solve
How many moles of magnesium is 1.25 X 1023 atoms of
magnesium?
Converting moles to number of particles
Conversion factor
Converting Moles to Particles
How many atoms can be found in 3.91 moles of xenon?
Converting Moles to Particles
• How many particles of sucrose are in 3.50 moles of
sucrose?
3.50 mol sucrose x 6.02 x 1023 rep. part.
1mol
2.11 x 1024 particles of sucrose
Solve
How many cadmium atoms are there in 6.57 × 103
moles?
• 2. How many molecules are in 2.00 moles of H2O?
Conv. Factor(s) Set-Up
• 3. How many atoms are in 2.00 moles of H2O?
Conv. Factor(s) Set-Up
• How many moles are in 6.02 x 1023 atoms of carbon?
Conv. Factor(s)
Set-Up
• 10. If you have 0.00812 mole of H2CO3, how many molecules do you
have?
Conv. Factor(s)
Set-Up