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Molar Mass

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Molar Mass

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  1. Molar Mass Using Molar Mass as a Conversion Factor

  2. Molar Mass • A molar mass is the mass in grams of one mole of a substance. • One mole of any substance contains Avogadro’s number of particles. • 6.022 x 1023 particles. • Calculated by adding together the masses of all of the individual atoms in a chemical formula. • Units are grams per mole (g/mol). • Example – KClO3 • K = 39.10g x 1 atom = 39.10g • Cl = 35.45g x 1 atom = 35.45g • O = 16.00g x 3 atoms = 48.00g • 39.10 + 35.45 + 48.00 = 122.55 g KClO3

  3. Practice Problems • Complete practice problems. • Solutions: • H2SO4 = 98.09 g • Ca(NO3)2= 164.10 g • PO43- = 94.97 g • MgCl2 = 95.21 g • Na2SO3 = 126.06 g • HClO3 = 84.46 g • MnO4- = 118.94 g • C2H6O = 46.08 g

  4. Molar Mass as a Conversion Factor • Molar mass can be used to convert between: • Moles of a substance and grams of a substance. • Grams of a substance and moles of a substance. • Equations: • x = grams • x = moles

  5. Converting Moles to Grams What is the mass in grams of 2.50mol of oxygen gas (O2)? • Step 1: Calculate molar mass. • 16.00 + 16.00 = 32.00 g • Step 2: Use equation: • x = 80.0 g O2 • Solutions: • 2. 51.87g NH3 • 3. 43g Ca(NO3)2 • 4. 1,303g Fe2(SO4)3

  6. Converting Grams to Moles How many moles are there in 3.82g of sulfur dioxide(SO2)? • Step 1: Calculate molar mass. • 32.07 + 16.00 + 16.00 = 64.07 g • Step 2: Use equation: • x = 0.0596 molSO2 • Solutions: • 2. 2.385 mol • 3. 1.09 mol • 4. 0.25 mol