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B1 powerpoint

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IB Chemistry III B1 presentation.

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B1 powerpoint

  1. 1. B1: ENERGYB.1.1. Calculate the energy valueof a food from enthalpy ofcombustion data
  2. 2. USE THE EQUATION Q = MC ΔTq = change in heat or energy (J) m = mass (g) c = specific heat (J/g K) ● ΔT = change in temperature (K)
  3. 3. BOMB CALORIMETRY The specific heat used will be that of water (about 4.184 J/g °C) because the reaction to find q will take place in a bomb calorimeter like the one pictured here
  4. 4. BOMB CALORIMETRY The food is placed in the steel “bomb” where it is combusted The ignition unit causes the combustion to occur within the bomb by heating up the sample The thermometer measures the temperature increase as the reaction within the bomb occurs, the water absorbing the heat that is released The stirrer ensures that the water’s temperature is staying the same within the dewar
  5. 5. USE THE EQUATION Q = MC ΔT Ifasked to find the calories in the food (rather than Joules), convert q to calories by dividing the number of Joules by 4.184 The answer is generally in the form of J/g, kJ/g, J g/mol, kJ g/mol, cal/g, kcal/ ● ● g, etc.*** 1 cal = 4.184 J ***
  6. 6. EXAMPLE 1#
  7. 7. EXAMPLE 2
  8. 8. EXAMPLE 3
  9. 9. SOURCES http://www.fao.org/DOCREP/006/Y5022E/ y5022e04.htm http://www.chem.hope.edu/~polik/Chem345-2000/ bombcalorimetry.htm

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