Molar heat of combustion of an alkanol (1 Viewer)

[Krocodile]

Hey everyone. I'am currently first in my chem class and i was away for this prac. The problem being a have an assessment task in 2 weeks on this prac, this is what i have to do.

Design and carry out an investigation to determine the molar heat of compustion of an alkanol. Evaluate the validity and reliability of the investigation.

Anyone got any tips, i have a good idea but i would like some help.

thanks~

 

[pLuvia]

Try using the search function before posting a question because chances are the question may have already been answered

Anyway I wrote this up quite a while back, hope it helps

http://community.boredofstudies.org/2205713/post-3.html

 

[Krocodile]

Thanks heaps, and thanks for the tip.

 

[Forbidden.]

Yes ... now I don't have to rely entirely on my prac book for my Chem exam next week ... Who's got good exam responses for Lelanche cells ?

EDIT: Hold on, which mass do I calculate in the ΔH = mCΔT equation ? The spirit burner, amount of water+beaker or both ?

 

[tennille]

I think m is the mass of the water in the beaker (I haven't done heat of combustion since high school).

 

[idling fire]

Yes ... now I don't have to rely entirely on my prac book for my Chem exam next week ... Who's got good exam responses for Lelanche cells ?

EDIT: Hold on, which mass do I calculate in the ΔH = mCΔT equation ? The spirit burner, amount of water+beaker or both ?

You have to do each object separately. The spirit burner has nothing to do with it at the moment. Use mass of water with specific heat capacity of water and temperature of water to find ΔH water. Same goes for the beaker (although you have to use temperature of water for this one as well unfortunately). Then add them together.

As a note, this value is equal to ΔH fuel, since that is all the heat released.

Then yeah, heat of combustion per gram = (ΔH fuel)/(mass of fuel)

 

[Sam.]

And make sure that you have the mass of the water and the specific heat capacity of water in the same units (ie. both in grams or both in kilograms). A lot of people get caught out and end up with a ΔH that is either way to high or way too low.

 

[gerg tenrab 07]

and to get the molar heat of combustion, once uve got the heat of combustion per gram, multiply it by the molar mass in grams

 

[yoakim]

AND if you want the heat of combustion per gram, divide ΔH by grams of fuel.
Just remember these two formulas:

q=mCΔT

ΔH=q/n --> where n=m/MM

 

[ram14]

Hey has anyone got the resluts for this experiment i missed its as well but the teacher gave us this whole sheet giving us the whole experiment...Aim, method, calculation etc...but i dont have the results so if anyone has the
Initial Mass
Final Mass
Initial Temp.
Final Temp

For ethanol, 1-propanol and 1 butanol