Mole

1
Mole

• amount of substance containing the same number of
  particles as 12 g of C-12.
• 1 mole contains 6.02 x 1023 particles (Avogadros
  number)
• Particles may be atoms, molecules, ions

2
Check for Understanding

• How many atoms are there in 1.0 mole sample of
  Fe?
• How many molecules are there in 2.5 moles of CO2?

3
Molar Mass

•  

1 mole C-12 6.02 x 1023 atoms 12 g
1 mole CO2 6.02 x 1023 molecules 44 g
4
Molar Mass

• Molar mass
• mass of 1 mole of a substance (in grams)
• equals the total mass of all the atoms in a
  substance
• What is the molar mass of H2O?
• H O
• 2 moles 1 mole
• 2 (1g) 2g 1(16g) 16g
• 2g 16 g 18 g
• The molar mass of H2O is 18g.

5
Molar Mass

• What is the molar mass of Mg(OH)2?
• Mg H O
• 1 mole 2 moles 2 moles
• 1(24g) 24 g 2 (1g) 2g 2 (16g) 32g
• 24g 2 g 32 g 58 g
• The molar mass of Mg(OH)2 is 58g.

6
Objective

• Do mass-mole conversions.

7
Mole Mass Conversion
/ Molar Mass
Mass
Mole
x Molar Mass
Sample Problem 1 What is the mass of 0.25 moles
of H2O? Mass of H2O 0.25 mol x 18 g
mol 4.5 g
8
Mole Mass Conversion
/ Molar Mass
Mass
Mole
x Molar Mass
Sample Problem 2. How many moles are there in 36
g of H2O? Moles of H2O 36 g x 1 mol
18g 2.0 mol
9
Check for Understanding

• Do the following conversions
• 1) 25 g NH3 _____ moles
• 2) 0.75 g Cl2 _____ moles
• 3) 3.0 moles Fe _____ grams
• 4) 4.5 moles KNO3 _____ grams