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Unit V: The Mole

Dilutions. What’s a Mole?. Molar Concentration. Molar Mass. Unit V: The Mole. Empirical & Molecular Formulae. Molar Volume. Percent Composition. Density & Molar Volume. Review of Unit Conversions.

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Unit V: The Mole

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  1. Dilutions What’s a Mole? Molar Concentration Molar Mass Unit V: The Mole Empirical & Molecular Formulae Molar Volume Percent Composition Density & Molar Volume

  2. Review of Unit Conversions • In Raiders of the Lost Ark, Indiana Jones tried to remove a gold idol from a booby-trapped pedestal. He replaces the idol with a bag of sand. If the idol has a mass of 20.00 kg, how many litres of sand must he place on the pedestal to keep the mass sensitive booby-trap from activating? (Density of sand is 3.00 kg/L) • What is equivalent in this example? 3.00 kg of sand = 1L of sand • What conversion factors can be made from this equivalency? or • What is our starting value? 20.00kg • Solve by writing your starting value, then using conversion factors that cancel out your units: 20.00kg x = 6.67L of sand

  3. Review of Unit Conversions • The density of cedar is 0.38 g/mL. If a dried cedar log has a mass of 23.1kg, what is its volume in L? • What is equivalent? 0.38g = 1mL 1kg = 1000g 1L = 1000mL • What is our starting value? 23.1kg • Solve by writing your starting value, then using conversion factors that cancel out your units: 23.1kg 60.8L

  4. Unit Conversions Practice • A student bragged that she went for a 1.5 x 1013 nm run last night. Keep her honest by expressing this distance to kilometers. Is this an impressive distance or not? • The earth is 1.496 x 108 km from the sun. A ‘light-second’ is the distance that light will travel in one second (in a vacuum) and is 2.998 x 105 km. How many light-seconds is earth from the sun? • How many minutes does it take sunlight to hit earth?

  5. Counting Molecules • You’re thirsty and you want some water, but all you have is oxygen and hydrogen. You’ve got 20kg of hydrogen, how much oxygen will you need so you don’t waste any? 2H2+O2 2H2O • This reaction suggests that you need twice as manyhydrogen molecules (H2) as oxygen molecules (O2). • However, this does not mean we need twice as much mass in hydrogen as oxygen, because oxygen molecules are much heavier than hydrogen molecules. • If you chose to only use 10kg of oxygen to mix with 20kg of hydrogen, you would make 5.6L of water. However, with the right amount of oxygen you could actually make 360L of water from 20kg of hydrogen. • We get around this problem using a different unit for quanitity: the mole

  6. What’s a Mole? • A mole is a (large) number of things. It allows us to count large groups of atoms and molecules on the scale that we can see. • As there are 12 eggs in a dozen eggs, there are 6.02 x 1023eggs in a mole of eggs • 6.02 x 1023is known as Avogadro’s Number 2 12 20 13 6.02 x 1023

  7. The Heart of the Mole Conversion Sheet Number of Particles Mole (mol)

  8. Using Avogadro’s Number • How many helium atoms are in 3.4 moles of helium? • If you have 9.124 x 1025 sugar molecules, how many moles of sugar molecules do you have?

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