Talk:Collision theory

Alternate theories

Does anyone know if there were ever (or are still) any alternate theories of chemical reactions besides this one? If so, they should probably be mentioned somewhere here. Lenoxus 12:02, 16 May 2006 (UTC)

To clarify the above: "(or are still)" is a silly-sounding phrase for those who understand that this is the most widely accepted theory and there is no real controversy. That said, I'm still extremely curious about whatever historically came "before", if anything...--Lenoxus 04:37, 23 January 2007 (UTC).

As far as i know there are no previous formal theories (but there are many later better ones), but there have been theories in the 18th century, talking about spiky molecules which locked into molecules with holes. Knights who say ni 08:03, 23 January 2007 (UTC)

Do you have a name or a reference or a name on this "spiky molecule / hole molecule" theory? If so, I can add it to the History of the molecule article. --Sadi Carnot 06:45, 24 January 2007 (UTC)

Transition state theory also explains temperature dependence of reaction rates.--Theislikerice (talk) 17:05, 21 February 2011 (UTC)

Comment

Some dude went in and edited, but didn't edit their coding enough. So, basically, it has been rendered unreadable. Please fix? February 18, 2012 — Preceding unsigned comment added by 24.7.115.35 (talk) 07:29, 19 February 2012 (UTC)

Please add some more :) I am year 10 and need it for coursework. July 10, 2006 User:195.93.21.65

If you're in year ten in the UK, doing your GCSEs, this is a bit much... this is year 13 (A Level Chem) and higher stuff. CPCHEM 00:10, 19 August 2006 (UTC)

I started this in year 10, and now i need to know more about it in year 11 for my GCSE coursework...82.39.98.11 16:19, 19 September 2006 (UTC)

It's likely it's only REFERRED to; they use it in biology to say "reactions occur with more energy in them". This is very very very unlikely to be fully required for GLUCOSE as it's mathematically very advanced in some states (Eigenstates occur in collision theory of quantum physics). Even A-Level Chemistry doesn't even touch upon these kinds of calculations, it's just Entropy relation. ♥♥ ΜÏΠЄSΓRΘΠ€ ♥♥ ^{slurp me!} 22:00, 28 April 2007 (UTC)

I'm afraid that we do actually have to do collision theory in year 11 in the UK, we have to do practical coursework on it in my school! (80.4.6.192 (talk) 20:50, 27 November 2008 (UTC))

derivation of the exponential factor

In all articles related to the Arrhenius equation it is stated that the exponential factor stems from an integral over the Maxwell-Boltzmann distribution. Can anyone show how this is actually derived? —Preceding unsigned comment added by 84.191.237.160 (talk) 18:54, 16 December 2007 (UTC)

Citation needed

"it is not feasible to establish, on the basis of temperature studies of the rate constant, whether the predicted T½ dependence of the preexponential factor is observed experimentally". The citation seems to be Kenneth Connors, Chemical Kinetics, 1990, VCH Publishers (according to http://www.bookrags.com/wiki/Arrhenius_equation#cite_note-Connors-1). If someone has access to the book and confirm this source, please edit the article to include it.--Theislikerice (talk) 17:05, 21 February 2011 (UTC)

Collision Frequency

The collision frequency is:

$Z=N_{A}\sigma _{AB}{\sqrt {\frac {8k_{B}T}{\pi \mu _{AB}}}}$

where:

• N_A is the Avogadro constant
• σ_AB is the reaction cross section
• k_B is Boltzmann's constant
• μ_AB is the reduced mass of the reactants.

Something is wrong with this equation. Z should have units of time^-1. However, given [N_A]= 1, [σ_AB] = Length², and [${\sqrt {\frac {8k_{B}T}{\pi \mu _{AB}}}}$]= length time^-1. This gives Z units of Length³ time^-1, when surely it should have units of time^-1, given it's a frequency. Should the concentrations of A and B not appear in the equation, given they have units of length^-3, so would cancel correctly? TwigHK (talk) 17:18, 10 March 2014 (UTC)

No. This is an example for a bimolecular gas phase reaction. So [$dc/dt=-kc^{2}$] (for equal start concentrations of both reactands) and thus k has to be in units of length^3/time in to cancel out the second concentration term. 16:35 1 July 2014 — Preceding unsigned comment added by 134.106.218.119 (talk) 14:36, 1 July 2014 (UTC)

Errors in explanation for pre-exponential factor of Arrhenius equation

"When the expression form of the rate constant is compared with the rate equation for an elementary bimolecular reaction, $\scriptstyle r=k(T)[A][B]$, it is noticed that $k(T)=N_{A}^{2}\sigma _{AB}{\sqrt {\frac {8k_{B}T}{\pi m_{A}}}}\exp \left({\frac {-E_{a}}{RT}}\right)$."

This formula seems wrong. Why is there an N_A² in the formula? Why does it say m_A in the root instead of the reduced mass as in all equations beforehand? From my understanding, it should be $k(T)=N_{A}\sigma _{AB}{\sqrt {\frac {8k_{B}T}{\pi \mu _{AB}}}}\exp \left({\frac {-E_{a}}{RT}}\right)$, i.e. exactly the same as in the equations before, only without [A][B].

I agree with your assessment of this issue Your fellow human (talk) 13:31, 26 October 2017 (UTC)your_fellow_human

Errors with location of pi on this page

It seems to me that the <math>\pi<\math> should be in the numerator since in collision theory a factor of <math>\pi<\math> is multiplied by the average velocity term due to the circular geometry of the sphere collision. Here is a published paper using it in the numerator and here is a national lab paper about with it also in the numerator (no subscription needed). I am just looking for verification before I change the actual page.

This seems to be an issue when on the page <math>\sigma_{AB}<\math> is converted to <math>r_{AB}^2<\math>, which seems to be missing <math>\pi<\math>.

Your fellow human (talk) 13:38, 26 October 2017 (UTC)

References