1 / 13

Calorimetry

Thermochemistry. Calorimetry. The Measurement of Heat Transfer in Chemical Reactions. Conservation of Energy. In interactions between a system and its surroundings the total energy remains constant: Energy is neither created nor destroyed. q system + q surroundings = 0.

kasen
Download Presentation

Calorimetry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Thermochemistry Calorimetry The Measurement of Heat Transfer in Chemical Reactions

  2. Conservation of Energy In interactions between a system and its surroundings the total energy remains constant: Energy is neither created nor destroyed qsystem + qsurroundings = 0 qsystem = -qsurroundings

  3. Heats of Reaction • Heat of reaction, qrxn • The quantity of heat exchanged between a system and its surroundings when a chemical reaction occurs within the system, at constant temperature. The flame produces energy, one form of which is heat, q

  4. Heats of Reaction • Exothermic reactions • Produce heat, qrxn < 0 • Endothermic reactions • Absorb heat, qrxn > 0 • Calorimeter • A device for measuring quantities of heat produced or absorbed in a chemical reaction q is signed

  5. Polystyrene Foam Cup Calorimeter • A simple calorimeter • Well-insulated; nearly isolated • Measure temperature change of solution inside qrxn + qsoln = 0 qrxn is extensive (units are J) DHrxn = qrxn/n is intensive (units are J/mol)

  6. Polystyrene Foam Cup Calorimeter • A simple calorimeter • Well-insulated; nearly isolated • Measure temperature change of solution inside qrxn + qsoln = 0 qsoln is extensive (units are J) qsoln = msolncsolnDTsoln

  7. Polystyrene Foam Cup Calorimeter • A simple calorimeter • Well-insulated; nearly isolated • Measure temperature change of solution inside qrxn + qsoln = 0 Can be expanded to… nDHrxn + msolncsolnDTsoln = 0 + Energy produced in the reaction Energy absorbed by the medium = 0

  8. Heat of Combustion of Fuels • DHcombustion relates to the economy of the fuel as an energy source • Two ways to report: • qcombustion per gram of fuel • qcombustion per mole of fuel • This week: Determine the amount of energy produced (per g and mol) for the combustion of • ethanol • diesel fuel, C14H30 (similar to kerosene or lamp oil)

  9. A Simpler Calorimeter • A soda can and an “alcohol” burner. • Not well insulated. • Measure temperature change. qrxn + qwater  0 Can be expanded to… nDHcomb + mwatercwaterDTwater 0 + Energy produced by combustion Energy absorbed by the water  0

  10. Simple Combustion Calorimeter qrxn + qwater = 0 q = mcDT (used for solutions and water) q = nDH (used for reactions)

  11. Notes for Lab This Week • Total volume should be constant for all runs • Accurate values for DH will not be determined… …but relative values between two fuels will be • How will you know how many moles of fuel were burned? • How will you determine the quantity of heat absorbed by the water in the aluminum can calorimeter?

  12. What Data Should I Collect? • Mass of fuel burned • Volume (or mass) of water heated • Temperature change of water This investigation, Author 1: Introduction and Conclusion 2: Discussion 3: Data/Results and Experimental This investigation, Author A: Introduction, Conclusion, Data/Results B: Discussion and Experimental

More Related