1 / 21

Energy Transfers Using a calorimeter

You can work out four things: Energy released by fuel in Joules Energy released by fuel in kilojoules Energy released by fuel in Kilojoules/gram Energy released by fuel in Kilojoules/mol. Energy Transfers Using a calorimeter. Worked example:

blake-dalton
Download Presentation

Energy Transfers Using a calorimeter

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. You can work out four things: Energy released by fuel in Joules Energy released by fuel in kilojoules Energy released by fuel in Kilojoules/gram Energy released by fuel in Kilojoules/mol Energy Transfers Using a calorimeter Worked example: A fuel heated 40g of water which started at temperature of 20 degrees Celsius and finished at a temperature of 39 degrees. The fuel before burning had a mass of 23.6g but now has a mass of 23.5g. The fuel has a formula mass of 28.

  2. Your go: • A fuel heated 50g of water which started at temperature of 16 degrees Celsius and finished at a temperature of 41 degrees. The fuel before burning had a mass of 25.8g but now has a mass of 25.6g. The fuel has a formula mass of 46. • Work out the energy released in joules, kilojoules, kilojoules/gram and kilojoules/mol.

  3. Energy Level Diagrams

  4. Copy and complete: An ______________________ can be used to show how the energy stored in chemicals changes during a chemical reaction. In ______________ reactions the products have more energy than the ___________. In exothermic reactions the ____________ have less energy than the __________. A catalyst __________ the __________ energy. It does this by providing __________________________ ________. A catalyst is not ________________________. energy level diagram endothermic reactants products reactants activation lowers an alternate route for the reaction. used up during the reaction.

  5. 3.4 Bond Energies Objective: to explain how the balance of energy changes when bonds are broken or made, and how this affects the overall energy change of a reaction Outcomes: All: I can state what happens to energy when bonds are made and broken (D/E) Most: I can assign bond energies to an energy level diagram (C) Some: I can calculate the energy transferred in reactions using supplied bond energies (A/B) Homework: Revise for test on 3.1, 3.2 and 3.3 Due: Thursday 21 March Keywords: energy level diagram, exothermic, endothermic, bond energy

  6. I can state what happens to energy when bonds are made and broken (D/E) bond breaking = energy IN ENDOTHERMIC bond making = energy OUT EXOTHERMIC

  7. Each bond has a different bond energy. The amount of energy it takes to make OR break it. A H-H bond has a bond energy of 436kJ/mol Data on bond energies can be used to calculate the TOTAL energy of a reaction. This is the difference between the energy put in when bonds are made and the energy given out when bonds are broken.

  8. CH4(g) + 2O2(g) CO2(g) +2H2O(l) 804 Work out the bond energies for: a) the reactant molecules b) the product molecules Hence c) workout the overall energy change

  9. ________ ____________ _____ ________ ________ ____________ CH4(g) + 2O2(g) CO2(g) +2H2O(l) CH4(g) + 2O2(g) CO2(g) +2H2O(l) Add labels and energy values to the energy level diagram for the reaction. I can assign bond energies to an energy level diagram (C)

  10. Fuel Issues

  11. Briefly Summarise: Why Hydrogen fuel cells are less harmful to the environment than another example fuel (3).

  12. 3.4 Bond Energies Objective: to explain how the balance of energy changes when bonds are broken or made, and how this affects the overall energy change of a reaction Outcomes: I can state what happens to energy when bonds are made and broken (D/E) I can assign bond energies to an energy level diagram (C) I can calculate the energy transferred in reactions using supplied bond energies (A/B) Homework: Revise for test on 3.1, 3.2 and 3.3 Due: Thursday 21 March Keywords: energy level diagram, exothermic, endothermic, bond energy

  13. Example 1 Ethanol + Oxygen Water + Carbon Dioxide a) Complete the balanced symbol equation. b) Draw the structural formula. c) Calculate the energy in for the reactant bonds being broken. d) Calculate the energy out for the product bonds being made. e) Work out the overall change in energy BOND ENERGY (kJ/mol) C-H 413 O=O 498 C-C 347 C=O 732 O-H 464

  14. Example 2 Propane + Oxygen Water + Carbon Dioxide a) Complete the balanced symbol equation. b) Draw the structural formula. c) Calculate the energy in for the reactant bonds being broken. d) Calculate the energy out for the product bonds being made. e) Work out the overall change in energy BOND ENERGY (kJ/mol) C-H 413 O=O 498 C-C 347 C=O 732 O-H 464

  15. Example 3 Hydrogen + Nitrogen Ammonia a) Complete the balanced symbol equation. b) Draw the structural formula. c) Calculate the energy in for the reactant bonds being broken. d) Calculate the energy out for the product bonds being made. e) Work out the overall change in energy BOND ENERGY (kJ/mol) H-H 436 N-H 391 N≡N 945

  16. Example 4 Hydrogen + Oxygen Water a) Complete the balanced symbol equation. b) Draw the structural formula. c) Calculate the energy in for the reactant bonds being broken. d) Calculate the energy out for the product bonds being made. e) Work out the overall change in energy BOND ENERGY (kJ/mol) O=O 498 H-H 436 O-H 464

  17. Example 5 – A/S level question CHM2 Jan 2009

More Related