Determining the effect of carbon chain length of an alcohol on its fuel efficiency

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Determining the effect of carbon chain length of an alcohol on its fuel efficiency

  • Aim:  The aim of this experiment is to determine the enthalpy change of methanol, ethanol and propanol. Also to investigate how and why the molecular arrangement of the alcohol affects the enthalpy change.
  • Variables:
  • Independent Variable: Type of Alcohol
  • Dependent Variable: Change in Temperature
  • Controlled Variable: Mass of the calorimeter, Mass of water, Mass of the spirit burner
  • List of Apparatus: 
  • Clamp
  • Beaker (2*100cm3)
  • Calorimeter (Copper)
  • Methanol (200g)
  • Ethanol (200g)
  • Propanol (200g)
  • Weighing Balance (±0.01g)
  • Thermometer or Probe (-100C to 1100C, ±0.20C)
  • Spirit burner
  • Heating mat
  • Tripod
  • Pipe-clay Triangle
  • Safety Glasses
  • Aluminum Foil
  • Measuring Ruler (±0.05cm)
  • Procedure:
  • Set up the stand and the clamp at a set height above the wick of the spirit burner.
  • Weigh 20.00 grams of water on a pre-weighed beaker using a 2 d.p weighing balance.
  • Put the 20.00 grams of water in the calorimeter and record its temperature using a probe of thermometer.
  • Support the calorimeter on the clamp and stand it over the spirit burner containing methanol, the liquid alcohol to be tested.
  • Weigh the spirit burner, record its mass and replace the burner under the calorimeter and light the wick.
  • Note: Make sure the stopper remains on the spirit burner up until the spirit burner is lit to prevent alcohol from evaporating thus leading to a change in mass.
  • Light the spirit burner and use the thermometer or probe to stir the water at all times it is being heated. Heat the water until it reaches 300C.
  • Extinguish the spirit burner by placing it’s stopper on top the wick and keep stirring the water and note down the highest temperature it reaches.
  • Re-weigh the spirit burner and record the mass of alcohol that has been burned.
  • Record all results on a suitable table and repeat this procedure for the other alcohols.
  • Controlling Variable:
  • Mass of the calorimeter: This variable shall be controlled by using the same calorimeter for all experiments.
  • Mass of water and Mass of the Spirit Burner: These shall be controlled by measuring the net weight using a 2 d.p weighing balance.
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Data Collection and Processing:

 n=m/M (This formula is used to determine the moles of alcohol that was burnt)

Then Q=mcT to determine the heat energy given out by each alcohol.

Finally enthalpy of combustion is determined by using the formula H=mcT

Quantitative Data:

Calculation for Methanol:

Initial Mass of the Spirit Burner = 207.89g ± 0.01g

Final Mass of the Spirit Burner = 207.59g ± 0.01g

Mass of ethanol burned =0.30g ± 0.02g

Molar Mass of Methanol ...

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