3 replies to this topic

[juzer]

If i have the data of ultimate analysis, proximate analysis and flue gas analyser data
can i derive the molecular formula of a solid fuel(eg. coal) . If not what more data do i need. I have no way of getting its molecular weight.
Thanks
Juzer

[Shivshankar]

Hi Juzer,

Hope this helps.

http://majarimagazin...ample-analysis/
http://www.ems.psu.e...oal_formula.gif
http://www.ems.psu.e...dovic/coal.html


Regards
Shivshankar

[juzer]

Dear Shivshankar,

That solves the problem.
Only thing is we do not get the exact "molecular formula" by these methods.
Is there any way to get the exact formula using this data only.

Thanks
Juzer

[kkala]

I think there is no need to specify a molecular formula. The empirical formula is adequate for stoichiometric calculations. Consider celluloid for example, http://en.wikipedia.org/wiki/Cellulose, formula (C6H5O5)n. Products per kg of cellulose burnt will be same, whether we consider n = 1 or 2 or any. So we can consider n=1 for simplification.
When we analyse a pure substance, we first measure the % content of each of its elements to arrive at its empirical formula. Then we have to measure its molecular weight to arrive at the molecular formula. The latter is useful in estimating e.g. osmotic pressure or freezing point lowering concerning solutions of the substance. But concerning stoichiometry, the empirical formula ( http://en.wikipedia.org/wiki/Empirical_formula) as above seems adequate.
On the other hand no molecular formula is assumed to exist for mineral carbon, being a mixture of carbonification products (that may be weakly bonded to each other?). Not knowing the exact structure of it, I assume that any derived empirical formula for a specific carbon deposit aims at representing its composition in a brief form to facilitate stoichiometric and similar calculations.
Distinct molecules (hence MW) is understood not to exist in crystallized solids, even though we may say e.g. MW=58.5 for NaCl ( actually NaCl is empirical formula for n=1). For polymers MW of same batch varies within a range, and other amorphous solids (starch, cellulose, etc) have variable MW.

Edited by kkala, 04 June 2012 - 05:27 AM.