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Calorimetric Equations II and Delicious Applications

Calorimetric Equations II and Delicious Applications. Putting it Together. Calorimetry. What is Calorimetry ? What is a Calorimeter?. Three Assumptions of Simple Calorimeters:. No heat is transferred between the calorimeter and the outside environment

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Calorimetric Equations II and Delicious Applications

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  1. Calorimetric Equations II and Delicious Applications Putting it Together

  2. Calorimetry • What is Calorimetry? • What is a Calorimeter?

  3. Three Assumptions of Simple Calorimeters: • No heat is transferred between the calorimeter and the outside environment • Any heat absorbed or released by the calorimeter materials, such as the container, is negligible • A dilute aqueous solution is assumed to have a density and specific heat capacity equal to that of pure water (1.00g/ml and 4.184 J/g°C)

  4. Solution • Combustion • Neutralization • (Vaporization)

  5. Remember what we’ve seen • ΔH = nΔHx • ΔHsystem = ±|qsurroundings| • q = mcΔT • n = m/MM n = C x V

  6. Doing Calorimetric problems is about using these equations ΔH = nΔHxΔHsystem = ±|qsurroundings| nΔHx = qsurroundings nΔHx= mcΔT n = mcΔT / ΔHx m/MM = mcΔT / ΔHx

  7. Calorimetry of Solution • One substance dissolves in another NaBr(s) Na+(aq) + Br-(aq)

  8. Heat of Solution Demo • http://www.teachersdomain.org/resource/lsps07.sci.phys.matter.dissolvesalt/

  9. Calorimetry of Combustion • Burn a substance in oxygen to yield CO2 and H2O C3H8(l) + 5O2(g) 3CO2(g) + 4H2O(l)

  10. Question 3 • If the molar enthalpy of combustion of propane is -2220KJ/mol, what mass of propane will have to be burned in order to raise the temperature of 1.00L of water from 50.0 to 85°C.

  11. Question 4 • A calorimeter (C=0.850J/˚C) containing 5.00 x 102 ml of water at 22 oC is warmed to 100oC when 9.00 g of cheddar cheese is burned. Calculate the heat absorbed by the water and the heat of combustion, per gram, of cheese.

  12. Calorimetry of Neutralization • Acid + Base  Salt + Water • HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l) • Use the same strategy for other reactions • CuSO4(aq) + 2NaOH(aq) → Cu(OH)2(s) + Na2SO4(aq)

  13. Neutralization demo • 50ml of 1 mol/L HCl (strong acid) • 50ml of 1 mol/L NaOH (strong base) • HCl + NaOH NaCl + H2O

  14. Question 5 • A chemist wanted to find the heat of neutralization of HCl with NaOH. She added 61.1ml of 0.543M HCl to 42.6ml of 0.779M NaOH. The initial temperature of both solutions was 17.8oC and the highest recorded temperature of the solution after neutralization was 21.6˚C. What is the enthalpy of neutralization of HCl? • ASSUME: The density and heat capacity of the solutions is the same as that for pure water

  15. Question 6 • 50.0 mL of 0.300 mol/L CuSO4 solution is mixed with an equal volume of 0.600 mol/L NaOH. The initial temperature of both solutions is 21.4oC. After mixing the solutions in the coffee-cup calorimeter, the highest temperature that is reached is 24.6oC. Determine the enthalpy change of the reaction. • CuSO4(aq) + 2NaOH(aq) → Cu(OH)2(s) + Na2SO4(aq)

  16. But wait, there’s more… • Heat of Vaporization H2O(l) + ∆H  H2O(g)

  17. How a fridge works

  18. Heats of Vaporization • Freon – qvap 232kj/kg • Water – qvap 2257 kj/kg • Propane – qvap428 kj/kg • Ammonia – qvap 1369 kj/kg • Ethyl Alcohol – qvap 846 kj/kg

  19. So Why Use Freon • Unreactive • Chemically Safe • High qvap • Boiling point below target temp • WHY NOT? • Chlorofluorocarbon • BAD FOR THE ENVIRONMENT!!!!

  20. Making Ice Cream Who knew thermochemistry could taste so good?

  21. Ingredients • (½ cup) 125ml Milk (we’re using 2%) • (½ cup) 125ml Cream (we’re using 35%) • (¼ cup) 67.5g Sugar • (¼ tsp) ~1ml Vanilla Extract/flavouring For the bag: • (½ to 1 cup) 250g Sodium Chloride • (2 cups) 500g ice

  22. Heat of Solution • Why are we adding salt? • What does salt do to the melting point/freezing point of ice/water? • Why not just use ice? • Why not use a more endothermic substance i.e. NH3NO3? • Why do we salt our roads?

  23. Recipe…I mean…Procedure • Add ingredients to small bag • CLOSE IT TIGHTLY (push out most of the air) • Put the small bag in the big bag • Add ice and salt to the big bag • CLOSE IT TIGHTLY • Swish the big bag back and forth • Caution: it will get really cold (duh…but seriously, its colder than you’d think)

  24. Mr. Sheps Ice Cream Attempts • Which one has sugar? Which one has a higher fat content?

  25. Let’s Make Ice Cream

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