0
$\begingroup$

The Wegscheider condition restricts the values that rate constants in a set of chemical reactions can take on. can someone please explain intuitively why the condition has to be true, and give a simple example of a set of reactions and rate constants that violate it? why could such a system not exist physically?

$\endgroup$
  • $\begingroup$ The Detailed Balance In Wikipedia page has details on this condition. In a system of reversible reactions it seems to boil down to the Law of Mass Action. $\endgroup$ – porphyrin Jun 16 at 13:43
  • $\begingroup$ @porphyrin ... and $K_{1+2} = K_1 * K_2$, i.e. Gibbs energy is a state function. $\endgroup$ – Karsten Theis Jun 16 at 14:13
  • $\begingroup$ @porphyrin that page is dense and lacks simple example. does wegscheider imply that in $A \rightarrow^{k_1} B, B \rightarrow^{k_2} A$ we must have $k_1 \times k_2 = 1$? what defines a "cycle"? Is this a cycle? $\endgroup$ – bal Jun 16 at 15:36
  • $\begingroup$ No, the product of rate constants can have any positive value $\gt 0$. If $K^e$ is the overall equilibrium constant for a series of equilibria,$\ce{A<=>B<=>C<=>} \cdots $ then $K^e=K_1^eK_2^e\cdots $ where $K_i^e$ are the individual equilibrium constants, $K_1^e=k_1/k_{-1}=\mathrm{[B]/[A]}$ etc. for rate constants $k_1, k_{-1}$. (Unless you absolutely have to, don't bother with this Wegscheider stuff unless you really want to dig around in the fundamental math of differential equations as applied to chemistry. ) $\endgroup$ – porphyrin Jun 16 at 16:15

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.