8 replies to this topic

[kuldeep singh]

How to calculate the Activation Energy and rate constant of the Chlorine forming a free radical.

Cl2 forming Cl dot.

Regards
Kuldeep

[kkala]

http://onlinelibrary...030105/abstract could be useful as general reference, though not free (24 h "rent" possible).

http://www2.fiu.edu/...l reactions.pdf '> http://www2.fiu.edu/...l reactions.pdf is understood to state activation energy = +243 kJ/ mol Cl2 (gas), concerning its dissociation into free radicals Cl^. , same as bond enthalpy of Cl2 (gas). See pages 5-6, chlorination.

http://jcp.aip.org/r...isAuthorized=no '> http://jcp.aip.org/r...isAuthorized=no concerns Cl2 - Ar mixture (1:5) under high temperatures and shock waves (??); yet activation energy of Cl2 dissociation is not far from above value.

Bond enthalpy of Cl2 (gas) has some variation (239-243 kJ/mol) depending on source.
Rate constant A of Arrhenius equation has not been found, first mentioned reference could be useful for it.

[kuldeep singh]

Dear Sir

The same thing i found out on google but the problem is different.

Regards
Kuldeep

[kkala]

Can you explain in more detail, so that some member could help?
A clarification probably useful: Energy of activation and bond enthalpy (and heat of reaction) are not generally same. But second web reference of post No 2, box "Activation Energies for Chlorination of Methane" says following.
When using enthalpy values (ΔH^o) the term for the difference in energy between starting material and the transition state is the energy of activation (E_act)...........
Step 1 Chain initiation Cl2-->2Cl^. E_act=+243 kJmol^-1 .
Look also at box "Chlorination" below the mentioned one (page 5).
Comments from others welcomed too.

Edited by kkala, 27 December 2012 - 05:39 AM.

[markymaark]

Are you talking about in an aqueous solution? If so, that would just be the dissociation energy

[kuldeep singh]

Dear Sir

the chlorine forming a free radical is a reversible reaction. i want to find out the rate constant of forward as well as backward reaction with respect to temperature and Eo of the reaction.

Regards
Kuldeep

[kkala]

The only additional info found is that "The degree of thermal dissociation of Cl₂ + 243 kJ ^-->_<-- 2Cl is 2.07 × 10^–4 percent at 1000°K and 0.909 percent at 2500°K", http://encyclopedia2.thefreedictionary.com/Chlorine+gas. This is probably at 1 Atma total pressure, but not clarified.
Above dissociation of Cl2 molecule (homolytical split) into two identical free radicals (atoms) occurs in gaseous state (by heat or UV light).

I think activation energy for Cl2-->2Cl^. (rate constant k1) is 239-243 kJ/mol as above. If rate constant of reverse reaction is k2, equilibrium constant is equal to k1/k2.

Edited by kkala, 28 December 2012 - 06:51 AM.

[kuldeep singh]

thank you sir for your great help and support. does anyone tell me the good software of molecular modelling...

Regards
Kuldeep

[kuldeep singh]

where do i find a good software of molecular modelling

Regards
Kuldeep