Gram Formula Mass (Molar Mass)

1
Gram Formula Mass(Molar Mass)

• Unit 6 - Bonding

2
Gram Formula Mass

• How many atoms of each element are in a formula
  unit of each compound?
• NaCl
• 1 Na and 1 Cl
• Fe2O3
• 2 Fe and 3 O
• (NH4)2S
• 2 N, 8 H, 1 S
• Al2(SO4)3
• 2 Al, 3 S, 12 O

3
Gram Formula Mass

• GFM mass (in grams) of 1 mole of an ionic
  compound (molar mass)
• Just add up all of the pieces of the compound

4
Gram Formula Mass

• NaCl
• 22.99 35.45
• 58.44 g/mol
• Fe2O3
• 2(55.85) 3(16.00)
• 159.70 g/mol

5
Gram Formula Mass

• (NH4)2S
• 2(14.01) 8(1.01) 32.07
• 68.17 g/mol
• Al2(SO4)3
• 2(26.98) 3(32.07) 12(16.00)
• 342.17 g/mol

6
GFM Calculations

• Now use the calculated GFM to do mole
  conversions.
• Like
• How many moles is ____ g of _____?
• What is the mass of ____ mole of ____?

7
GFM Calculations

1. How many moles is 2.63 g of NaCl?
2. What is the mass of 3.78 moles of Fe2O3?

2.63 g NaCl
1 mol NaCl

0.0450 mol NaCl
58.44 g NaCl
3.78 mol Fe2O3
159.70 g Fe2O3

604 g Fe2O3
1 mol Fe2O3