Enthalpy change data Watch

madele
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I'm stuck!

I've just started an Access course in Science (so I can study a bioscience degree). I haven't done Chemistry since GCSE 12 years ago and that was obviously different to what I'm doing now (Level 3 work).

I'm doing an assignment on energetics and I need to find out and give the standard enthalpy changes of the combustion of propanol and the neutralisation of sodium chloride and hydrochloric acid. I've tried Googling but I don't know what sources (from the VERY few I could find - nothing that seems decent) would be considered reputable. I'm hoping someone could point me in the right direction.

Thanks!
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charco
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(Original post by madele)
I'm stuck!

I've just started an Access course in Science (so I can study a bioscience degree). I haven't done Chemistry since GCSE 12 years ago and that was obviously different to what I'm doing now (Level 3 work).

I'm doing an assignment on energetics and I need to find out and give the standard enthalpy changes of the combustion of propanol and the neutralisation of sodium chloride and hydrochloric acid. I've tried Googling but I don't know what sources (from the VERY few I could find - nothing that seems decent) would be considered reputable. I'm hoping someone could point me in the right direction.

Thanks!
For thermodynamic data try the NIST chemistry webbook site.

If you are having trouble navigating it just ask.

Don't forget that propanol is a liquid, so you should look at the condensed phase data ...
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madele
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Thanks. I found that website before and you are right to think I wouldn't understand how to use it!
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charco
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(Original post by madele)
Thanks. I found that website before and you are right to think I wouldn't understand how to use it!
click the link...

go to 'search options'

select condensed phase data

put 1-propanol into the search field press enter

scroll down to read all energy data ...
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madele
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OK got it, thank you. Where can I look to find the standard enthalpy change for the neutralisation reaction between sodium chloride and hydrochloric acid?
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madele
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Also I'm wondering if it seems reasonable that my own results for the combustion of propanol would be about 60% lower than the standard figure. I knew it'd be less but that much less?! I feel I must be doing something wrong.

:confused:
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charco
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(Original post by madele)
OK got it, thank you. Where can I look to find the standard enthalpy change for the neutralisation reaction between sodium chloride and hydrochloric acid?
Sodium chloride does not react with hydrochloric acid ...

... you mean sodium hydroxide.

The enthalpy of neutralisation data is freely available - just google it...
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charco
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(Original post by madele)
Also I'm wondering if it seems reasonable that my own results for the combustion of propanol would be about 60% lower than the standard figure. I knew it'd be less but that much less?! I feel I must be doing something wrong.

:confused:
It would be expected to be considerably lower, but in reality it is very difficult to comment on your data without seeing both it and the calculations employed ...
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madele
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(Original post by charco)
Sodium chloride does not react with hydrochloric acid ...

... you mean sodium hydroxide.

The enthalpy of neutralisation data is freely available - just google it...
Doh I did mean hydroxide. I hadn't been looking for sodium chloride!

The reason I asked this question though is because I don't know what sources are considered reliable, not because I can't find a figure.
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charco
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(Original post by madele)
Doh I did mean hydroxide. I hadn't been looking for sodium chloride!

The reason I asked this question though is because I don't know what sources are considered reliable, not because I can't find a figure.
Most sources will be reliable as the data is very well known ...
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madele
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(Original post by charco)
It would be expected to be considerably lower, but in reality it is very difficult to comment on your data without seeing both it and the calculations employed ...
OK this is the data I recorded:

0.99g of propanol was burnt raising the temperature of 100ml water by 33 degrees C.

So of course I did 4.18 x 0.1 x 33 = 13.794

and to get 1 mole 60 x 13.794 / 0.99.

So the enthalpy change for the combustion of one mole of propanol is -836kJ according to me. According to proper sources it is about -2021!
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charco
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(Original post by madele)
OK this is the data I recorded:

0.99g of propanol was burnt raising the temperature of 100ml water by 33 degrees C.

So of course I did 4.18 x 0.1 x 33 = 13.794

and to get 1 mole 60 x 13.794 / 0.99.

So the enthalpy change for the combustion of one mole of propanol is -836kJ according to me. According to proper sources it is about -2021!
1. You have lots of heat losses to the environment
2. You have also heated up the calorimeter and thermometer
3. Some energy is used to evaporate the water
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madele
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OK, as long as I haven't done my calculations wrong I am happy Thanks.
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