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Toxic Alcohols in Spirit Burners to test Fuel Efficiency

Submitted by sat on 21 June 2016

In brief:

Under controlled circumstances this practical activity is safe to conduct. However the quantity of spirit burners: four sets of six alcohols per class equals 24 spirit burners, which is a considerably high number and would be associated with risks such inadequate ventilation for a class with 25 students. Oxygen from the room is used up during the combustion reactions and there is an increase in the level of carbon dioxide gas, which can lead to headache, dizziness and fatigue. Science ASSIST strongly recommends that this experiment be conducted as a teacher demonstration or by dividing the class into six groups, with each group investigating one alcohol under an operating fume cupboard or in a well-ventilated room.

Fuel efficiency can be investigated by determining the heat of combustion of fuels such as alcohols using spirit burners. When alcohols are burnt in oxygen, a large amount of heat is released and the reaction is said to be exothermic.

All the alcohols mentioned are safe to use in the spirit burner and Science ASSIST recommends the following:

Safety notes:

Additional Information

Methanol, ethanol, propan-1-ol, butan-1-ol,pentan-1-ol and hexan-1-ol are all aliphatic alcohols with the general formula CnH2n+1 OH where n is greater than or equal to 1. The functional group is the hydroxyl group (–OH). Alcohols are good fuels as they burn in oxygen to give a large amount of heat. The standard enthalpy change of combustion of a compound is the heat change that occurs when 1 mole of a substance is completely burned in oxygen under standard conditions (at 1 atmosphere pressure and at 25OC).

The equations for the combustion of methanol and ethanol are:

CH3OH(l) + 1 1/2O2(g) → CO2(g) + 2H2O(g)      ∆HOC=-726 kJmol-1

C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(g)     ∆HOC= -1367 kJmol-1

A known mass of alcohol is burned in a spirit burner and the heat released is transferred to a copper can containing a known volume of water. From the resulting temperature rise, the enthalpy of combustion of ethanol can be calculated. As the number of carbon atoms increases the enthalpy change of combustion becomes more negative.

∆HOC= Mass X Specific heat capacity X Rise in temperature

          = mc∆T 

During this experiment the volume of water used and the distance between the wick of the spirit burner and the bottom of the calorimeter should be kept constant.

References

‘Butan-1-ol’, Safety Data Sheet, Chem-Supply website, https://www.chemsupply.com.au/documents/BA0121CH1H.pdf (June 2014)

‘Butan-1-ol’, Please visit the Sigma-Aldrich website for their latest Safety Data Sheet: https://www.sigmaaldrich.com/australia.html

‘Hexan-1-ol’, Safety Data Sheet, Chem-Supply website, https://www.chemsupply.com.au/documents/HL0101CHIM.pdf (February 2016)

‘Hexan-1-ol’, Please visit the Sigma-Aldrich website for their latest Safety Data Sheet: https://www.sigmaaldrich.com/australia.html

‘Methanol’, Safety Data Sheet, Chem-Supply website, https://www.chemsupply.com.au/documents/ML0041CH4F.pdf (July 2011)

‘Pentan-1-ol’, Safety Data Sheet, Chem-Supply website, https://www.chemsupply.com.au/documents/PL0491CH4W.pdf (August 2011)

‘Propan-1-ol’, Safety Data Sheet, Chem-Supply website, https://www.chemsupply.com.au/documents/AR1161M.pdf (April 2011)