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Thermo-chemistry

Calculate the volume of gas released at 227 o C under 83.1 kPa pressure when 16 kg of NH 4 NO 3 is exploded forming N 2 , O 2 , & H 2 O:. Thermo-chemistry. Thermochemistry. The study of heat transfer in chemical reactions. Thermochemistry. Heat change Calorimetry TCE.

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Thermo-chemistry

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  1. Calculate the volume of gas released at 227oC under 83.1 kPa pressure when 16 kg of NH4NO3 is exploded forming N2, O2, & H2O:

  2. Thermo-chemistry

  3. Thermochemistry • The study of heat transfer in chemical reactions

  4. Thermochemistry • Heat change • Calorimetry • TCE

  5. Thermo-chemical Terms

  6. System • That part of nature upon which attention is focused

  7. Surroundings • That part of nature around the part upon which we are focused

  8. Reaction Coordinate • A graph of energy change versus time in a chemical reaction

  9. P Energy R Time

  10. Exothermic Rxn • Chemical reactions that release, give off heat, or lose heat

  11. Endothermic Rxn • Chemical reactions that absorb, take in heat, or gain heat

  12. Heat Change

  13. Specific Heat • The heat required to raise one gram of a substance 1oC • C: (J/goC, J/kgoK)

  14. Sp. Heat DH = mCDT

  15. Heat of Fusion • The heat required to melt one gram of a substance at its normal MP • Hf: (J/g or J/kg)

  16. Heat of Fusion DH = mHf

  17. Heat of Vaporization • The heat required to boil one gram of a substance at its normal BP • Hv: (J/g or J/kg)

  18. Heat of Vap. DH = mHv

  19. Calculate the heat change when 10.0 g H2O goes from –100.0oC to 200oC.MP = 0oC BP = 100oCHf = 334 J/g HV = 2260 J/g Cice = 2.06 J/gK Cwater = 4.18 J/gK Csteam = 2.02 J/gK

  20. Drill: Calculate the heat required to change 25 g of water from 140.0oC to 60.0oC MP = 0oC BP = 100oCHf = 334 J/g HV = 2260 J/g Cice = 2.06 J/gK Cwater = 4.18 J/gK Csteam = 2.02 J/gK

  21. Calorimetry • Experimental measure of heat transfer

  22. Calorimeter • Device used to measure heat transfer • A calorimeter is an adiabatic system • Experimental yield

  23. Adiabatic System • A system that exchanges zero heat with its surroundings DHsystem = 0

  24. DH (J) DH = q = the heat or enthalpy change in a system DHsys = mCDTsysparts

  25. Calorimetry DHsystem = 0 DHsys = DHcal + DHrxn DHrxn = -DHcal DHrxn = -mCDTcal

  26. When Q reacts in a 1.5 kg calorimeter containing 2.5 kg water ch. from 22.5oC to 26.5oC. Calculate DHrxn. Cwater = 4.18 J/gK Ccal = 2.00 J/gK

  27. When X reacts in a 2.0 kg calorimeter containing 1.5 kg water went from 22.5oC to 30.5oC. Calculate DHrxn. Cwater = 4.18 J/gK Ccal = 1.50 J/gK

  28. Homework • Problems 7 & 8 • On page 234

  29. Thermo-chemical Equation Terms

  30. Typical Reaction • HCl + NaOH  NaCl + HOH

  31. Heat of Reaction • The heat or enthalpy change of a chemical reaction DHrxn

  32. Typical Ionization HCl  H+(aq) + Cl-(aq)

  33. Heat of Solution • The heat or enthalpy change when a substance is dissolved DHsoln

  34. Combustion Reaction • CxHy + O2 • CO2 + HOH

  35. Heat of Combustion • The heat or enthalpy change when a substance is burned DHcombustion

  36. Rxn Making Cpds from ele H2 + ½ O2 H2O

  37. Heat of Formation • The heat required to form one mole of a compound from pure elements DHfo (kJ/mole)

  38. The Degree Symbol • Indicates standard conditions & molar quantities by itself or from a balanced equation.

  39. Enthalpy • Heat flow in a system DH

  40. Gibb’s Free Energy • Energy of a system that can be converted to work • Determines spontaneity DG

  41. Energy of Formation • The energy required to form one mole of a compound from pure elements DGfo (kJ/mole)

  42. Exergonic Reaction • A reaction in which free energy is given off DG< 0

  43. Endergonic Reaction • A reaction in which free energy is absorbed DG> 0

  44. Exergonic Reaction • A reaction which can be spontaneous DG< 0

  45. Endergonic Reaction • A reaction which cannot be spontaneous DG> 0

  46. Reaction at Equilibrium DG= 0

  47. Interrelation Term (DG) DG interrelates thermochemistry, chemical equilibria, & electrochemistry

  48. Entropy • A measure of disorder DSo

  49. Entropy of Formation • The entropy of one mole of a substance • Sfo (J/moleoK)

  50. Drill: Define: • Heat of reaction • Heat of solution • Heat of formation • Energy of formation • Entropy of formation

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