Unit 5: The Mole and Unit 5: The Mole and StoichiometryStoichiometry

Mole as a BridgeMole as a Bridge

Moles and GasesMoles and Gases At standard temperature and pressure At standard temperature and pressure

(STP) . . . (STP) . . . 1 mole of 1 mole of anyany gas will occupy the same gas will occupy the same

volume as volume as anyany other gas at the other gas at the same same temperature and pressure.temperature and pressure.

At STP (which is 0At STP (which is 0ooC and 1 atm):C and 1 atm): 1 mole1 mole of any gas occupies a volume of of any gas occupies a volume of

22.4 liters.22.4 liters.

Therefore, Therefore, 1 mole = 22.4 liters1 mole = 22.4 liters (of any gas at STP)(of any gas at STP)

ExamplesExamples:: What is the volume of 0.0035 moles What is the volume of 0.0035 moles

of CHof CH44 at STP? at STP?

0.0035 moles

1 mole

22.4 Liters

= 0.078 Liters CH4

What is the number of moles of What is the number of moles of oxygen in an 85 Liter sample at STP?oxygen in an 85 Liter sample at STP?

What is the mass of 18 liters of What is the mass of 18 liters of carbon dioxide gas at STP?carbon dioxide gas at STP?

85 Liters22.4 L

1 mole = 3.8 moles

18 Liters 22.4 L

1 mole 44.01 g CO2

1 mole= 35 grams

One Mole can equal 3 different One Mole can equal 3 different thingsthings

1. 1. 6.02 X 106.02 X 102323 atoms or molecules atoms or molecules

2. 2. The mass of any element or The mass of any element or molecule molecule in gramsin grams

3. 3. 22.4 Liters of22.4 Liters of any gasany gas at Standard at Standard Temperature and Pressure (STP)Temperature and Pressure (STP)

Since the mole can equal any one Since the mole can equal any one of these, it can also serve as a of these, it can also serve as a bridgebridge to convert from one to to convert from one to another of them.another of them.

Mole as a BridgeMole as a Bridge

Mole

Mass(Molar Mass)

Volume(22.4L)

Particles(6.02 x 1023)

“x”

“x”

“x”“÷”

“÷”

“÷”

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

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

Using the Mole as a Bridge Using the Mole as a Bridge Examples:Examples:

How many grams are there in 7.4 x How many grams are there in 7.4 x 10102323 molecules of AgNO molecules of AgNO33??

7.4 x 1023 molecules

6.02 x 1023 molecules

1 mole AgNO3 1 mole

AgNO3

169.87 g

= 209 grams = 210 grams (sig figs!)

Using the Mole as a Bridge Using the Mole as a Bridge ExamplesExamples

How many molecules are there in How many molecules are there in 230 grams of CoCl230 grams of CoCl22??

230 g CoCl2129.83 g CoCl2

1 mole

1 mole

6.02 x 1023 molecules

= 1.07 x 1024 molecules

Using the Mole as a Bridge Using the Mole as a Bridge ExamplesExamples

What is the volume of 150 grams of What is the volume of 150 grams of NN22O gas at STP?O gas at STP?

150 g N2O

44.02 grams

1 mole

1 mole

22.4 L

= 76.3 Liters