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Stoichiometry Review

Stoichiometry Review. What is a mole?. Definitions: A mole ( mol ) is a unit used for measuring atoms, molecules, or other particles A mole is equal to the number 6.022 x 10 23 A mole was the name given to the quantity of atoms in exactly 12 grams of carbon-12. Molar Mass.

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Stoichiometry Review

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  1. Stoichiometry Review

  2. What is a mole? • Definitions: A mole (mol) is a unit used for measuring atoms, molecules, or other particles • A mole is equal to the number 6.022 x 1023 • A mole was the name given to the quantity of atoms in exactly 12 grams of carbon-12

  3. Molar Mass • The molar mass of an element or compound is the mass of exactly one mole of that element or compound • Units are grams per mole (g/mol) • To find molar mass, add up the masses from the periodic table for the compound • Ex: H2O = H + H + O • H = 1.01 O = 16.00 • 1.01 + 1.01 + 16.00 = 18.02 g/mol

  4. Converting between Grams and Moles • To convert between grams and moles, use the molar mass as a conversions factor • (molar mass) grams = 1 mole • Ex: How many grams in 2 moles of water? • Molar mass of water (H2O) = 18.02 g/mol

  5. Converting between Atoms/Molecules and Moles • Use Avogadro’s number as a conversion factor • 1 mole = 6.022 x 1023 atoms/molecules/particles • Ex: How many moles in 1.2044 x 1024 molecules of H2O?

  6. Converting between Liters of a gas and Moles • Use the volume of a gas at STP • 1 mole of a gas at STP = 22.4 L • Ex: How many liters would 3 moles of He occupy at STP?

  7. Converting between Moles of two different compounds or elements • This only applies when we have a chemical equation to work with! • To convert, use the mole ratio as your conversion factor • Ex: For the equation 2 H2 + O2 2 H2O, if I have 3.4 moles of H2, how many moles of O2 do I need? • Mole Ratio (from coefficients) 1 mol O2 : 2 mol H2

  8. Mole Island • The following chart can help you remember how to convert between units as well as how to string together multi-step conversions! • Just find your starting and ending points, then do each conversion you cross along the path.

  9. Converting from grams of one element/compound to grams of another • Follow the mole island path! • Example: N2 + 3 H2 2 NH3 • For the above reaction, how many grams of nitrogen gas would I need to make 10 g of NH3? • Grams of NH3  moles of NH3  moles of N2  grams of N2 Start Molar Mass NH3 Mole Ratio Molar Mass N2 Answer

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