Missed 2 pracs (1 Viewer)

[Mannie]

Hey all.

I was just wondering if anyone would be able to help me because i missed two pracs last term.-- 1. Comparing the heats of combustion of alcohols and 2. Identifying an unknown alkanol using heat of combustion.

Any help would be greatly appreciated thanks.

 

[insert-username]

1. Comparing the heats of combustion of alcohols

i. A small amount of a given alcohol was added to a spirit burner and the burner weighed.

ii. 750g of water was added to an aluminium can weighing 21.7g. The temperature of the water was taken and recorded.

iii. The burner was lit and placed under the can. A thermometer was used to stir the water continually.

iv. Once the water had risen in temperature by around 10 degrees, the burner was extinguished and reweighed. The highest temperature reached by the water was recorded.

v. Using the molecular weight and the mass change of the alcohol, the change in temperature of the water, and the specific heat capacity of water, the molar heat of combustion and heat of combustion per gram of the alcohol was calculated.

My class didn't do the identify an unknown alkanol using heat of combustion - it's not in the syllabus, from memory, but I'm sure someone else here has done it and can help you.


I_F

 

[pLuvia]

Well my one was combined, and it was an assessment so it was pretty big

I basically used the same method as insert-username, we had methanol, ethanol and 1-propanol and were asked to estimate the HOC of 1-butanol

You should see that the graph produced, using the heat of combustion, is nearly constant but the results you shall get will not be the same as a lot of energy is lost during the experiment

If you like I can send you my whole experiment, just PM me

 

[Dreamerish*~]

This is a wonderful site by Jamesy, who kindly uploaded most science pracs - you can look for the HOC prac there.

http://www.geocities.com/jamesyscien...c/pom/exp.html

 

[Riviet]

If you are to conduct and write up this experiment, you need to keep all the controls the same, ie use the same amount of water, set up everything in the same way except for fuels of course, and use the same type of container to heat. Aluminium cans are better than beakers because they don't absorb the heat as much.

 

[pLuvia]

We had to use beakers when containing the water, thus the loss of so much energy, but in the end the trend of the graph was pretty much the same as the actual results

 

[Mannie]

Thanks every body for their help. Again much appreciated.

 

[pLuvia]

Here's my prac for Heat of Combustion feel free to take a look at it