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Science Dept.

Chemistry CHE 100 Notes
K. Stoichiometry

  1. Stoichiometry

    1. Definition:

    2. Types of Problems

      1. Mass to Mass

      2. Mass to Volume or Volume to Mass

      3. Volume to Volume

    3. The Road Map

      1. Mass to Moles Using the Periodic Table of the Elements

      2. Moles to Moles Using the Balanced Equation

      3. Moles to Mass Using the Periodic Table of the Elements

    4. Periodic Table of the Elements

      1. Atomic Mass or Weight

      2. Mole Concept

      3. Atomic Number

    5. The Balanced Equation

      1. See Guidelines in Chemical Equations

      2. Example: The complete oxidation of ethane

      3. _____ C2H6(g) + _____ O2(g) -----> _____ CO2(g) + _____ H2O(g) + E

  2. Let's Solve a Problem: Calculate the mass of oxygen needed for the complete oxidation of 72 grams of ethane

    1. (72g ethane) x (mole ethane/mass ethane) = (moles of ethane)

      1. The relationship needed is between mass of ethane and moles of ethane

        1. From the Periodic Table:

          1. C = 12 amu
          2. H = 1.0 amu
          3. C2H6 = 30 amu
          4. One mole of C2H6 = 30 grams
      2. (72g ethane) x (one mole ethane/30g ethane) = (2.4 moles of ethane)

    2. (2.4 moles ethane) x (moles O2/moles ethane) = (moles of oxygen)

      1. The relationship needed is between moles of ethane and moles oxygen

        1. From the Balanced Equation:

          1. There are 2 moles of ethane to 7 moles oxygen gas

      2. (2.4 moles ethane) x (7 moles O2/2 moles ethane) = (8.4 moles of O2)

    3. (8.4 moles O2) x (mass of O2/moles O2) = (mass of O2)

      1. The relationship needed is between one mole of O2 and the mass of O2

        1. From the Periodic Table:

          1. O = 16 amu
          2. O2 = 32 amu
          3. one mole of O2 = 32 grams

      2. (8.4 moles O2) x (32g of O2/one mole O2) = (268.8g of O2)

    4. Mass to Volume

      1. What is the volume of 268.8 g (or 8.4 moles) of O2?

      2. (8.4 moles O2) x (22.4l/mole of gas) = 188.2 liters of O2 at STP

 

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