An Analysis into how Degrees of Unsaturation of Hydrocarbons impact the enthalpy produced in a Combustion Reaction
Aim
To investigate the relationship between the degrees of unsaturation (DoU) and the amount of enthalpy, in a combustion reaction and to subsequently, determine whether a hydrocarbons hydrogen deficiency increases or decreases the enthalpy of a reaction.
Hypothesis
It is hypothesised that a hydrocarbon with a lower DoU value will produce more heat energy and, therefore, will have a lower enthalpy value. This is because a more saturated hydrocarbon produces a greater amount of energy in a combustion reaction1.
Variables
Variable
Method for measuring
Independent
DoU
Using the formula3
Dependent
Heat enthalpy
The mass of the alcohol burnt from each interval and trial for all alcohols, was recorded. Using this data, the following formula was used to measure the heat enthalpy4:
Controlled variable
How variable is controlled
Effect on results of not controlling variable
Distance between small can and spirit burner
This distance will always be 2cm between the wick and the base of the can, measured each time.
• increased distance would mean more heat loss to surroundings, thus, a slower increase in temperature for water, impacting the enthalpy calculations. Effect of a decreased distance is the opposite.
Equipment (can, balance and thermometer)
For each interval and trial the
• if the same can was used it would mean that the heat enthalpy would
* When we burn hydrocarbon fuels in the air the carbon and hydrogen in the fuel are completely oxidized. They produce carbon dioxide and water.
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Focus problem: Investigating the relationship between the relative molecular mass a primary alcohol and the respective enthalpy of combustion for that alcohol.
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An Investigation into the Enthalpies of the Combustion of Alcohols = == == == ==
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