Chapter 6 Lecture Outline


6.1 Chemical Hand Warmers


6.2 The Nature of Energy: Key Definitions

  1. Video Clip (George Gobel's Home Page, local)
  2. Limiting Reagent problem

  • Introduction to Thermodynamics
    1. Gummy Bear Animation ( internet © Saunders, 1997)
    2. What is energy (ability to do work, relative)
    3. Kinetic energy Ek = 1/2*m*v2 (Throw Chalk)
    4. Potential energy Ep = mgh (Drop Chalk)
    5. Chemical energy (stored in bonds)
      1. Endothermic
        1. Electrolysis of water (demonstrate)
        2. Dissolving salt (cold)
      2. Exothermic
        1. Combustion of gasoline
        2. Combustion of H2 and O2 (demonstrate)

    6. Units
      1. calorie (1 gram of water 1 C)
      2. Joule (SI Unit) kg m2/s2
      3. cal = 4.184 J
      4. Calorie=kilocalorie

    6.3 The First Law of Thermodynamics: There is No Free Lunch

    1. The law of conservation of energy.
    2. Energy content of the universe is constant.
    3. Energy can be neither created nor destroyed.
    4. No perpetual motion machines.
    5. Problems are worked in terms of the internal energy of a system E
    6. We can only measure the change in energy, /\E.
    7. What is a system?
    8. The change in internal energy is also related to heat (q) and work (w)
      E = q + w
    9. Concept of Change, Altitude Analogy
      1. Arbitrary Reference Point (sea level)
      2. Sign is significant
      3. Independent of Path
      4. Introduce Energy Level Diagram

    6.4 Quantifying Heat and Work

    1. Heat Transfer
      1. Macro scale video ( internet © Saunders, 1997)
      2. Micro scale animation ( internet © Saunders, 1997)

    2. Discuss Energy, Heat, and Temperature
    3. Example Problems

    6.5 Measuring E for Chemical Reactions: Constant-Volume Calorimetry


    6.6 Enthalpy: The Heat Evolved in a Chemical Reaction at Constant Pressure

    1. q = heat (Thermal Energy)
    2. w = work (P*V, change in volume, N=kg m sec-2, Pa=kg m-1 sec-2)
    3. [delta] E = q + w (Energy is heat plus work)
    4. IF volume is constant, no work, [delta] E = q
    5. IF pressure is constant, [delta] H = qp


    6.7 Constant-Pressure Calorimetry: Measuring Hrxn


    6.8 Relationships involving Hrxn


    6.9 Enthalpies of Reaction from Standard Heats of Formation

    1. Misc terms
      1. [delta] H Change in Enthalpy
      2. [delta] H° Change in Enthalpy at standard state
      3. [delta] Hf° Enthalpy of Formation at standard state
      4. Standard State 25C (298K) and 1 bar

    2. [delta] Hrxn = Hfinal - Hinitial
    3. Energy Diagram
    4. State Properties
      1. quantities
      2. pressure
      3. temperature
      4. volume
      5. physical state (ie: solid or liquid)

    5. Hess's Law Problems(sum of steps).
      1. Use energy level diagram to calcuate /\H for the following reaction: C (s) + 2 H2 -> CH4
      2. [delta] H for production of 500 g CCl4 based upon [delta] Hf and the reaction:
        CH4(g) + 4 Cl2 (g) -> CCl4 (l) + 4 HCl (g)

      3. Calculate [delta] Hrxn for the production of hydrazine rocked fuel and the amount of energy required to produce 1.00 kg of hydrazine formed from the reaction: (Ebbing page 252)
        N2 (g) + 2H2 (g) -> N2H4 (l)

      4. Calculate [delta] Hrxn for the combustion of gasoline and determine how much energy is released by burning 1 gallon of gasoline? (Density 0.7025 g/cm3)
        2 C8H18 + 25 O2 -> 16 CO2 + 18 H2O

      5. Calculate how much energy is required to produce 150 g of glucose ([delta]Hf = -1274 kJ mole-1, Aitkins) from CO2 and H2O

      6. The Ostwand process for nitric acid involves the following steps:
        4 NH3 (g) + 5 O2 (g) -> 4 NO (g) + 6 H2O (g)
        2 NO (g) + O2 (g) -> 2 NO2 (g)
        3 NO2 (g) + H2O (l) -> 2 HNO3 (aq) + NO (g)
        1. Find [delta] H for each reaction.
        2. Balance total reaction and find [delta] H.
        3. How much energy is required to produce 1000 kg of nitric acid?

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