Chemistry Lab 6 - Energy of Combustion
Rajesh Swaminathan
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Question: 
How can the energy of combustion of paraffin wax be found efficiently?

Hypothesis: Attached

Variables:

1. Independent:
2. Dependent:
3. Controlled:

Materials:

1. Paraffin wax candle.
2. Match/Lighter.
3. Large glass jar.
4. Test tube
5. Test tube holder
6. Thermometer
7. Small piece of plastic.
8. An index card to hold the candle.

Procedure:

1. Set up a candle on a piece of cardboard index card by fastening it
   with a bit of molten wax. Record the initial mass of the
   candle-cardboard setup.

2. Enclose the cardboard with a large-enough glass jar to prevent heat
   from escaping. The space on the top is required for oxygen to reach
   the flame to avoid incomplete combustion.

3. Record the mass of a Pyrex test-tube and clamp it to a test-tube
   holder. Lower the test-tube so that-tube so that it is about 2 to 3
   cms above the wick of the candle.

4. Fill the test-tube with 100 ml of cold, distilled water at ~10
   degrees C. Record the mass again, and a difference between this
   mass and the mass of the test-tube will give you the mass of the
   water inside the test-tube.

5. Close the open top of the test-tube with plastic or Styrofoam. Make
   a hole through this plastic and immerse the bulb of a thermometer
   into the water. Make sure there aren't any gaps between the
   thermometer and the plastic.

6. Accurately record the initial temperature of the water inside the
   test-tube with uncertainties.

7. Lift the setup carefully, and light the candle with a match or a
   lighter. Lower the setup immediately, and make sure the flame is
   directly below the test-tube.

8. Keep a watch on the thermometer and make note of any
   observations. Stir gently with the thermometer to facilitate even
   flow of heat currents. Blow out the flame once the temperature
   reaches about 40 degrees C. Keep stirring, and record the highest
   temperature attained with uncertainties.

9. Record the final mass of the candle-cardboard setup and calculate
   the change in mass of the candle.

10. Examine the bottom of the test-tube for any residue. Calculate the
    change in temperature (delta T) and calculate the energy absorbed
    by the water to in order to raise its temperature, given the
    specific heat of water is 4.18 J/g per degree C.

11. Assuming that the energy produced by the combustion of the candle
    was used entirely to raise the temperature of the water, determine the
    heat of combustion of paraffin (heat evolved per gram of paraffin
    burned). 

12. Assuming that the molar mass of paraffin is about 280 g/mol,
    calculate the molar heat of combustion of paraffin. Express the
    result in kJ/mol. Ascertain if the results agree with your
    hypothesis. Calculate percentage error by comparing your answer
    with the accepted values. Discuss heat loss factors that might have
    contributed to the inefficiency of the experiment.