Lecture 3 Thermochemistry

Lecture 3 Thermochemistry - CHEM 6BL Experiment 3:...

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Unformatted text preview: CHEM 6BL Experiment 3: Thermochemistry Instructor: Dr. S. Berniolles Page 1 Chemistry 6BL Lab/Course Schedule Chemistry 6BL Lab/Course Schedule Date Lecture & Exam Schedule Lab Period Lab Schedule Prelab & Report 1 Due Dates Apr. 20 Iron Complex Synthesis/Analysis (Expt. 4A/B) 1 st lab 2 nd lab EXTRA LAB: end Expt. 2/Start Expt. 3 Expt. 3 (Parts I-II) --- Prelab Expt. 3 Experiment 3: Thermochemistry Experiment 3: Thermochemistry The study of heat in chemical reactions 2 Heat energy RELEASED by a reaction: EXOTHERMIC Heat energy ABSORBED by a reaction: ENDOTHERMIC Heat Transfer Heat Transfer System or Endo Endo Exo Exo 3 System or Object Endo Endo (into) Exo Exo (out of) CHEM 6BL Experiment 3: Thermochemistry Instructor: Dr. S. Berniolles Page 2 Heat Transfer Between Systems Heat Transfer Between Systems Energy/Heat will transfer between two systems brough into contac 4 systems brought into contact Systems in contact will equilibrate Result is a change in temperature (i.e., heat flow ) Heat Flow Heat Flow Heat flow takes place between a system and (usually) the surroundings System/Object : water, metal, reaction mixt., etc. 5 Surroundings : liquid/solvent, beaker/container, atmosphere (ambient) Heat Flow Heat gained from surroundings = +ve ( T = +) Heat lost to surroundings (cooled) = -ve ( T= -) Heat Capacity Heat Capacity The amount of heat energy required to raise the temperature of a substance by 1 K (1C) 6 Two types of Heat Capacity: Specific Heat Capacity (c): J/K g Molar Heat Capacity (C): J/K mol CHEM 6BL Experiment 3: Thermochemistry Instructor: Dr. S. Berniolles Page 3 Heat Capacity & Heat Change Heat Capacity & Heat Change Molar Heat Capacity At constant pressure : C p 7 At constant volume : C v Experiment #3 done under constant P Heat capacity relates to heat change via: q p = nC p T or q = mc T Heat Capacities of Substances Heat Capacities of Substances Heat Capacity of water is large : C P = 75.3 J/Kmol c = 4.18 J/Kg C p = c M (where M = 18 g/mol) 8 C p c M (where M 18 g/mol) Molar Heat Capacities of (transition) metals are about equal: C P 26 J/Kmol Known as the Law of Dulong and Petit Relates to the very similar atomic structure of such metals Total Heat Change Total Heat Change Total Heat Change (during a reaction): q p = nC...
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Lecture 3 Thermochemistry - CHEM 6BL Experiment 3:...

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