1.4 Energetics
Posted by: intechemistry on: September 23, 2010
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8 Responses to "1.4 Energetics"
December 9, 2010 at 5:22 pm
Yes. You are right.
The standard state (most stable state) for C is graphite. Correctly written as C(s, graphite)
But sometimes people are a bit ‘casual’ and only write C(s)
There is only about about 4 kJ mol-1 between diamond and graphite.
[hummm. Altho now with carbon bucky balls, tubes and graphene, I don't think such lazyness is ok any more]
I don’t know of any exceptions.
December 9, 2010 at 5:43 pm
oh.ok.so dats means we are supposed to write C in graphite state right?
December 9, 2010 at 7:49 pm
If your doing a deltaH(f) and you write C(s, graphite)
you can’t be wrong, so yes, your right.
February 22, 2012 at 5:42 pm
Dear Sir. Can you outline the bullet points for U1 Edxcl ppr – preparation of double salt (& def of double salt), recrystallisation steps & IS THER ANY OTHER EXPERIMENT NEEDED TO BE COVERED B4 THE EXAMS? Tq 
February 23, 2012 at 7:42 pm
Dear Curious. I would be much more to your advantage if you wrote down what YOU think are the bullet points for making the double salt. After which I will comment on it.
If you read this http://www.edexcel.com/migrationdocuments/GCE%20New%20GCE/GCE_Chemistry_8CH01Practical_work_Mapping_Green.pdf you will have a firm handle on the kind of theoretical knowledge relating to practical techniques necessary for the exams. Also, make sure you read those practical sheets I gave out. They are VERY important)
Actually, this kind of info is best suited to the “U3 discussions” page
May 4, 2012 at 2:54 am
gud day sir
Q: how will the enthalpy of combustion differ if water in gaseous state is formed rather than on lid form (info on eq of combustion of propanal was provided in the question) ?
thanx in adv
May 4, 2012 at 12:18 pm
Good day to you too Draco.
Th combustion value will be less exothermic. Perhaps you can think about it this way: to go from H2O(l) to H2O(g) you need to put energy in.
How much ‘less exo’ depends of course on the specific energies involved.
I suppose it’s possible that it may be so much less exo that actually it turns out to be endo overall (a lot of energy is needed to produce steam), but I’d still guess the overall value will be exothermic.
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December 9, 2010 at 5:08 pm
salam sir.
sir, for a question regarding the enthalpy of formation of a substance, we suppose to write the element or substance for the reactants involved in their most stable state right?
or is there any exception?
there’s one question i did, the Carbon used is in the solid state not graphite as what I understood.