Chem Class- January 18, 2010

Today we did a lab in class on 'The Heat of Combustion of Candle (Paraffin) Wax. We were to find the heat that is released when one mole of Paraffin wax is burnt.

Materials:
candle

match

electronic weigh scale
lab stand
wire mesh or triangle

Thermometer

150 mL of cold water

A metal can

                                                                                            

Procedure:

1. Set up the lab the stand and wire mesh
2. Measure 150 mL of water and pour it into the metal can
3. Record the temperature of water and the mass of the candle before lighting it
4. Place the candle under the can and carefully light it
5. Let the candle burn for approximately five minutes and then record the new temperature of the water as well as the mass of the candle after the experiment
6. Clean up your lab station

                                                                              

We were also to make the following observations:

• The volume of water used
• The initial temperature of the water
• The initial mass of candle
• The final temperature of water
• The final mass of candle

                                                                                             

- With that information, we calculate the mass of Paraffin wax that was burn during the experiment (final mass-initial mass), the # of moles of Paraffin wax that was reacted during the experiment (number of grams x molar mass/ C25H52), the # of joules of energy that the water gained and determine the molar heat of combustion  (Joules/Mole) of Paraffin Wax.

- In addition, knowing that the accepted value for molar heat of combustion of Paraffin wax is approximately -14500 kJ/mol, we determine the percent error (Remember that the percent error is measure value- accepted value/ accepted value). We need to also keep in mind that there is a possibility of error such as miscalculations and changing ambient conditions

It was a simple and fun lab to do and it had a lot to do with what we were learning (Calorimetry and Enthalpy). Try it out yourself, and see if you come close to the accepted value for the molar heat of combustion of Paraffin Wax. Remember to wear your safety goggles and lab apron!