3 replies to this topic

[harinath reddy]

Hi ,
Can anyone please tell me at what temperature theCarbon and Hydrogen Bonds in Propane disassociates.

Thanks to everyone who can help me.

[gvdlans]

You suggest that there is one particular temperature above which the C-H bond will break. It doesn't work like that. The dissociation reaction is:

C3H8 <---> C3H7· + H·

Reaction speed can be modelled with the Arrhenius equation. Following is copied from http://www.shodor.or.../arrhenius.html

"Common sense and chemical intuition suggest that the higher the temperature, the faster a given chemical reaction will proceed. Quantitatively this relationship between the rate a reaction proceeds and its temperature is determined by the Arrhenius Equation. At higher temperatures, the probability that two molecules will collide is higher. This higher collision rate results in a higher kinetic energy, which has an effect on the activation energy of the reaction. The activation energy is the amount of energy required to ensure that a reaction happens.

k=A*exp(-Ea/R*T)
where k is the rate coefficient, A is a constant, Ea is the activation energy, R is the universal gas constant, and T is the temperature (in degrees Kelvin).

R has the value of 8.314 x 10-3 kJ mol-1K-1"

Following link seems also interesting: http://pubs.acs.org/.../jp030597f.html

[harinath reddy]

Thanks for your reply. Actually the way i asked the question is bit wrong.

For example consider Methane, Break down of methane hydrate commences at 272.8 K,approximately after 10 hours. At 273 K it achives 100% reaction in a reasonable time. Dissociation is complete after 3hours at 273.6 to 273.8 K and only 18 minutes at 288.8 K.
This is what i want to know for propane.
thanking you
Harinath Reddy Bussu

[gvdlans]

I would say that the melting of methane hydrate is more similar to melting of ice and that it can not be compared with the dissociation reaction of propane. My advise for you is to study reaction kinetics in more detail. You can start this by reading through the series that can be found on this website, starting with http://www.cheresour...kinetics1.shtml as well as the references in this series.