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Drill: Calculate mole fraction of:

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:. Drill: Calculate mole fraction of:. A solution containing 331 g Pb(NO 3 ) 2 in 1782 mL water. Thermo-chemistry. Chm II. Chapter 15. Thermochemistry.

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Drill: Calculate mole fraction of:

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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. Drill: Calculate mole fraction of: A solution containing 331 g Pb(NO3)2 in 1782 mL water.

  3. Thermo-chemistry

  4. Chm II Chapter 15

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

  6. Thermochemistry • Heat change • Calorimetry • TCE

  7. Thermo-chemical Terms

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

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

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

  11. P Energy R Time

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

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

  14. Heat Change

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

  16. Sp. Heat DH = mCDT

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

  18. Heat of Fusion DH = mHf

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

  20. Heat of Vap. DH = mHv

  21. 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/gC Cwater = 4.18 J/gC Csteam = 2.02 J/gC

  22. 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/gC Cwater = 4.18 J/gC Csteam = 2.02 J/gC

  23. Calorimetry • Experimental measure of heat transfer

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

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

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

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

  28. 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

  29. 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

  30. When Z reacts in a 1.0 kg calorimeter containing 2.0 kg water went from 22.5oC to 32.5oC. Calculate DHrxn. Cwater = 4.18 J/gK Ccal = 2.00 J/gK

  31. Drill: When 40.0 g NH4NO3 dissolves in 460.0 g water at 25.0oC, the temp. falls to 22.5.oC. Calculate the DHosoln for NH4NO3. Csoln = 4.00 J/gK

  32. Thermo-chemical Equation Terms

  33. Heat (H) • A form of energy that can flow between samples of matter

  34. Enthalpy • Heat that can flow in/out of a system DH

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

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

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

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

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

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

  41. Rxn Making Compounds from elements H2 + ½ O2 H2O

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

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

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

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

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

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

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

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

  50. Reaction at Equilibrium DG= 0

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