Unit 5: The Mole and Stoichiometry

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Unit 5 The Mole and Stoichiometry

• Mole as a Bridge

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Moles and Gases

• At standard temperature and pressure (STP) . . .
  
• 1 mole of any gas will occupy the same volume as
  any other gas at the same temperature and
  pressure.
• At STP (which is 0oC and 1 atm)
• 1 mole of any gas occupies a volume of 22.4
  liters.
• Therefore, 1 mole 22.4 liters
• (of any gas at STP)

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Examples

• What is the volume of 0.0035 moles of CH4 at STP?

0.0035 moles
22.4 Liters
1 mole
0.078 Liters CH4
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• What is the number of moles of oxygen in an 85
  Liter sample at STP?
• What is the mass of 18 liters of carbon dioxide
  gas at STP?

85 Liters
1 mole
3.8 moles
22.4 L
1 mole
18 Liters
44.01 g CO2
22.4 L
1 mole
35 grams
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One Mole can equal 3 different things

• 1. 6.02 X 1023 atoms or molecules
• 2. The mass of any element or molecule in grams
• 3. 22.4 Liters of any gas at Standard
  Temperature and Pressure (STP)
• Since the mole can equal any one of these, it can
  also serve as a bridge to convert from one to
  another of them.

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Mole as a Bridge
Mass (Molar Mass)

x

x
x
Particles (6.02 x 1023)

Volume (22.4L)

• Going out of the Mole, MULTIPLY (top of T-chart)
• Going into the Mole, DIVIDE (bottom of T-chart)

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Using the Mole as a Bridge Examples

• How many grams are there in 7.4 x 1023 molecules
  of AgNO3?

7.4 x 1023 molecules
169.87 g
1 mole AgNO3
6.02 x 1023 molecules
1 mole AgNO3
209 grams 210 grams (sig figs!)
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Using the Mole as a Bridge Examples

• How many molecules are there in 230 grams of
  CoCl2?

6.02 x 1023 molecules
230 g CoCl2
1 mole
129.83 g CoCl2
1 mole
1.07 x 1024 molecules
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Using the Mole as a Bridge Examples

• What is the volume of 150 grams of N2O gas at STP?

150 g N2O
1 mole
22.4 L
44.02 grams
1 mole
76.3 Liters