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The Mole Concept Chemistry What is a mole? • The mole is a unit used to measure very small quantities – Such as atoms, particles, molecules, ions, etc. – One mole = 6.022 x 1023 • The mole is similar to the concept of a dozen – One dozen = 12 = = One mole can represent many things! One dozen would be… • 12 eggs • 12 atoms • 12 chemistry teachers One mole would be… • 6.02 x 1023 eggs • 6.02 x 1023 atoms • 6.02 x 1023 chemistry teachers! Amadeo Avogadro • The concept of the mole is attributed to Avogadro, and is referred to as Avogadro’s number A Mole Can Represent Anything • • • • • Atoms Molecules Particles Planets Coins Mole Conversions • Example Problems 1. If I have 3 moles of He gas, how many particles is this? 1.81 x 1024 particles He 2. If I have 8.0 x 1024 atoms of iron, Fe, how many moles is this? 13.3 mol Fe Molar Mass • The mass of one mole of a substance – Based on their atomic masses on the periodic table – By convention, we will round atomic masses to 3 sig figs – Molar masses can be used as a conversion factor • Molar Mass has units of grams per mole (or g/mol) Molar Mass • Example Problems 1. What is the molar mass of iron? 55.8 g/mol Fe 2. How many grams of iron are there in 8.00 moles? 446 g Fe Molar Mass • Example Problems 3. How many moles are in 10.0 grams of magnesium? 0.412 mol Mg 4. How many moles are in 5.3 grams of boron? 0.491 mol B Molar Mass • Practice Problems 1. How many grams of sulfur are there in 2.5 moles? 80.3 g S 2. How many grams of aluminum are there in 2.00 moles? 54 g Al Molar Mass • Practice Problems 3. How many moles are there in 3.4 grams of carbon? 0.283 mol C 4. How many moles are there in 2.00 grams of neon? 0.099 mol Ne Molar Mass of Molecules • Using the molar mass for each element, find the total molar mass of a molecule • Example Problems 1. What is the molar mass of H2O? 18.02 g/mol H2O 2. What is the molar mass of CO2? 44 g/mol CO2 Molar Mass of Molecules • Practice Problems 1. What is the molar mass of C3H8? 44.1 g/mol C3H8 2. What is the molar mass of CH3I? 142 g/mol CH3I Molar Mass of Molecules • Example Problems 1. If I have 5.00 grams of NaCl, how many moles is this? 0.0901 mol NaCl 2. If I have 4.50 moles of water, H2O, how many grams is this? 81.1 g H2O Molar Mass of Molecules • How many particles are there in 3.00 grams of ammonia (NH3)? 1.06 x 1023 particles NH3 Molar Mass of Molecules • Practice Problems 1. How many moles are in 1.2 grams of methane gas (CH4)? 0.0665 mol CH4 2. How many grams are in 4.3 moles of propane (C3H8)? 189 g C3H8 Molar Mass of Molecules • How much do 1.3 x 1024 atoms of H2O weigh (in grams)? (2 steps!) 0.389 g H2O