Steady State Approximation and Reaction Mechanisms

[Gorby]

Hi,

I need help determining which of the statements are true and false.

http://imgur.com/9BC1Wqf

I know this involves steady state approximation, but I find that when I try it I am never able to rid of all the intermediates.

Please help

Thanks

 

[epenguin]

See rules at this site - show what you have attempted, see https://www.physicsforums.com/showpost.php?p=4354127&postcount=1. In this case we don't even know what your difficulty is as we don't know what equations are causing it.

Have you got an expression for [Br] in terms of [Br₂]?

 

[Chestermiller]

The way I start any problem like this is two write an equation for the time derivative d/dt of the concentration of each chemical species involved in terms of the concentrations of the various species and the reaction rate constants. Then, I set the time derivatives of the fast reactions equal to zero. This leads to algebraic expressions for the fast reactions. I then solve the algebraic equations for the concentrations of the short lived species (in this case free radicals) in terms of the long lived species concentrations. I then substitute the concentrations for the short lived species into the slow reaction time derivatives. This will always get you to where you want to be.

Chet