Out the bond energies of the alcohols in the homologous series up to Pentanol, comparing them to the data book values.

Planning:

Aim:

To try to work out the bond energies of the alcohols in the homologous series up to Pentanol, comparing them to the data book values. There are a few factors in these experiments that will affect our enthalpies (as opposed to the data book values), which will be outlined later on in the write-up.

Equipment:

An alcohol burner – This is the heat provider.

Heat proof mats – To insulate heat.

A stand + clamps – To support the experiment structurally.

A thermometer – To discern the starting and finishing temperatures.

50ml of water – Substance to be heated.

A copper can – Metal conductor of heat.

Electronic scales – To weigh the burners.

A measuring cylinder – To measure out the correct volume of water accurately.

Hypothesis:

I predict that the enthalpies of the alcohols will decrease as the number of carbons increases. The results should reflect the text book values to some extent and show a correlation between each other with a steadily decreasing trend (in terms of the enthalpy).

Factors:

Here are some of the factors that could have affected our results in some way or other:

There was no proper draught insulation – We only had heat proof mats to insulate the heat and to stop it from heating the surrounding air rather than the can containing the water.
The distance from the heat source and the can itself differed for some experiments as we did these experiments over a period of 3-4 lessons. Due to the switching of apparatus, we often had our cans adjusted to different levels, thus at different heights in relation to the alcohol burners.
Though the starting temperatures were generally similar as a whole, there were some different starting temperatures. However, these probably wouldn’t influence the results as much as the first factors mentioned above since we used the temperature range as the guideline, not the starting temperature itself. E.g. we used a 30°C temperature range for each alcohol.
We also have to take into account the relatively feasible margin of human error, seeing as our experiments were taking place in a packed laboratory in competitive conditions where the slowest to the mark runs the risk of getting the worst apparatus etc.
Even if we did have proper draught insulation we knew we’d have to live with the knowledge that not 100% of the heat given out by the alcohol burner would be used to heat the water in the can, but that inevitably the air around the alcohol burner would receive the heat from the alcohol burner too. But, seeing as the amount of heat absorbed by the surrounding air would be minimal and constant for all experiments, it probably wouldn’t have mattered.

Preliminary Experiment:

We all did a trial experiment to get a feel of the layout and processes involved in the experiment and also to establish how best to perform the experiment so we knew what we were doing when it came to the real thing. Each alcohol was tested twice to check for anomalies and to give more credence to our results – more sound evidence, more reliability.

Bond Energy Theory:

I’m basing my results on the theory of bond energy – which is defined as the amount of energy in kilojoules associated with the breaking or making ...