chapter 6

chapter 6 - Chapter 6 Thermochemistry 1 Thermodynamics is...

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Unformatted text preview: Chapter 6 Thermochemistry 1 Thermodynamics is the study of energy and its transformations in chemical and physical changes/reactions. E, w, q, H Calorimeter Heat of a reaction: Hesss Law, H o f, H from bond energies 6.1 The Nature of Energy 2 The Total Energy of the Universe is Constant . 1st law of thermodynamics 3 system surroundings System + surroundings = universe 4 system surroundings Energy lost by system = energy gained by surroundings Energy of universe = constant 5 Capacity to do WORK or produce Heat. 1 N = kg m/s 2 What is energy ? What is work ? Force acting over a distance. 6 What is heat ? The transfer of energy between two substances due to temperature difference. Temperature: a property that reflects the random motions of the particles in a substance. 7 8 funny (?) but wrong examples! Patricia Duff Energy can be converted from one to another form: Kinetic energy: due to motion and mass KE=1/2mV 2 Potential energy: due to position/composition 9 Two ways of energy transfer: through work or through heat. 10 E 1 Heat E 2 q and w are Path dependant Figure 6.1 a & b 11 E 1 E 2 Heat E 1 E 2 Work done The change in the potential energy is the same, regardless of the amount of heat and work. 12 State Function A properties of the system that depends only on its present state! The change in a state function in going from one state to another state is independent of the particular pathway taken between two states. The value of the a state function does not depend on how the system arrive at the present state. 13 Example: altitude, temperature Thermodynamic Quantities Magnitude and its sign 14 Figure 6.2 Exothermic Process q <0 Bond breaking: endothermic Bond formation: exothermic 15 Figure 6.3 Endothermic Process q>0 16 Are the following processes exothermic or endothermic? When solid KBr is dissolved in water, the solution gets colder Water is boiled in a kettle Water condenses on a cold pipe CO 2 (s) CO 2 (g) F 2 (g) 2F(g) (breaking a bond) 17 Sodium acetate heat pack: Heat of crystallization: heat is given off when sodium acetate crystallizes: provides the heat ! 18 system surroundings Internal energy = E sys Internal energy = E surr Internal energy: E = sum of all energies present 19 E 1 T= 10 o C Initial state E1 T= 5 o C Final state Define the system: water Surroundings: beaker + ice cube + . What has happened with respect to the system? E 2 System: water 20 T= 10 o C Initial state T= 5 o C Final state heat E 1 >E 2 E system = negative exothermic E= E 2-E 1 <0 System: water 21 Initial state T= 10 o C Final state (melts) heat E 2 >E 1 E = E 2-E 1 E system = positive endothermic T= 4 o C System: metal block water 22 Metabolic energy: burning of glucose C 6 H 12 O 6 P E CO 2 + H 2 O Energy released: E 1 E 2 E = E 2- E 1 HEAT synthesis transport Muscle contraction q w 23 E = q + w Heat work 24 STATE FUNCTIONS P, V, T, E, H q, w Non- STATE FUNCTIONS 25 C...
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This note was uploaded on 11/27/2011 for the course CHEM 101 taught by Professor Luikang during the Spring '10 term at SPSU.

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chapter 6 - Chapter 6 Thermochemistry 1 Thermodynamics is...

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