Chapter 3 Section 4 Notes

1
Chapter 3 Section 4 Notes

• Using Moles to Count Atoms

2
What is a mole?

• The SI base unit that describes the amount of a
  substance a collection of a very large number of
  particles.

3
What is a mole useful for?

• Counting small particles

4
Avogadros Constant

• Avogadros Constant the number of particles in 1
  mol
• Equals 6.022 x 1023 particles/ mol
• 602,213,670,000,000,000,000,000 particles
• How does Avogadros constant relate to a mole of
  something?
• It is the number of particles in one mole of
  anything.

5
Moles and Grams are related

• Molar Mass the mass in grams of 1 mol of a
  substance
• How do you find molar mass?
• The average atomic mass is equal to molar mass.
• Simply look on the Periodic Table!

6
Practice

• Determine the molar mass of the following
  elements (Round to the nearest hundredth)
• Manganese, Mn
• 54.94 g/mol
• Cadmium, Cd
• 112.41 g/mol
• Arsenic, As
• 74.92 g/mol
• Strontium, Sr
• 87.62 g/mol

7
More Practice

• Determine the mass, in grams of each of the
  following
• 0.48 mol of platinum
• 2.50 mol of sulfur

0.48 mol x
195.08 g

94 g
1 mol
2.50 mol x
32.07 g

80.2 g
1 mol
8
Even More Practice

• Determine how many moles are present in each of
  the following
• 620 g of mercury
• 11 g of silicon

620 g x
1 mol
3.09 mol
200.59 g
11 g x
1 mol
0.39 mol
28.09 g
9
Compounds also have molar mass

• To find the molar mass of a compound, add up the
  molar masses of all the atoms in a molecule of
  the compound.
• Example H2O
• Molar Mass of Hydrogen 1.01 x 2 2.02 g/mol
• Molar Mass of Oxygen 16 g/mol
• Total Mass of H2O 2.02 g 16 g 18.02 g/mol