Calorimetry

1
Calorimetry

• Experiment 5

2
The Calorimeter

• A calorimeter is a device that measures the
  amount of heat transferred during a reaction.
• Our calorimeter consists of two Styrofoam cups, a
  cardboard lid, a thermometer, and a wire stirrer.
  
• Keep in mind that our system includes all the
  components mentioned above.

3
Calorimeter Constant

• Your calorimeter will contribute to the total
  change in enthalpy of each reaction.
• You need to calculate the calorimeter constant
  (heat capacity of the calorimeter) in order to
  correctly calculate the enthalpy of each
  reaction.
• Ccalorimeter Qcalorimeter / DT
• Qwarm -(Qcold Qcalorimeter)

4
Heat Capacity

• Heat capacity ( C ) the amount of heat required
  to raise the temperature of an object or
  substance a given amount.
• Q is the quantity of heat transferred
• Q (specific heat) x (mass) x (DT)
• Specific heat - the amount of heat necessary to
  raise the temperature of 1g of a substance by
  1oC.
• Although your lab book uses C to symbolize both
  heat capacity and specific heat, keep in mind
  that they are different!

5
Enthalpy

• The heat of reaction, or change in enthalpy is
  represented by the symbol, DH.
• At constant pressure
• Q/mol DH.
• Exothermic (-DH) - heat is given off from the
  system and absorbed by the surroundings
• Endothermic (DH) - heat from the surroundings is
  absorbed by the system

6
Hesss Law

• Hesss Law states that the overall enthalpy
  change for a reaction is equal to the sum of the
  enthalpy changes for the individual steps in the
  reaction.
• DHoverall DHrxtn1 DHrxtn2

7
Notes on the Experiment

• You will perform all five choices in this
  experiment.
• Work by tables.
• Work on getting all your data for week 1 and we
  will work on calculations together for week 2.
• You must use the same (calibrated) calorimeter
  for all parts of the experiment. Store your
  calorimeter in your drawer, not your cabinet!
  Put the thermometer, stopper, and wire stirrer
  back on the cart.
• If your thermometer goes up in increments of 1
  degree, you can read it to the tenth decimal
  place.