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Unit 5: The Mole and Stoichiometry. Mole as a Bridge. 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 0 o C and 1 atm):
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Unit 5: The Mole and Stoichiometry Mole as a Bridge
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)
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
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
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 ofany 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.
Mole 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)
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!)
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
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