3
$\begingroup$

Suppose in a reaction vessel of fixed volume we have the following equilibria established (existing simultaneously in the vessel), \begin{align} \ce{A (g) &<=> B (g) + C (g)}\tag{i}\label{i}\\ \ce{D (g) &<=> E (g) + C (g)}\tag{ii}\label{ii} \end{align}

Frankly speaking I do know that when we increase, say, $\ce{A (g)}$ concentration in $\eqref{i}$ then indeed the concentration of $\ce{C}$ or $\ce{B}$ is going to increase as per Le Chatelier's Principle. However if we increase the concentration of $\ce{E (g)}$ in the vessel what impact will it have on the concentration of $\ce{C}$ and $\ce{A}$?

From my perspective, when $\ce{E}$ is increased in concentration, it will now combine with $\ce{C}$ to give $\ce{D}$ so that reaction goes backwards, and so more of $\ce{C}$ needs to be formed as a result $\ce{A}$ concentration in equilibrium $\eqref{i}$ goes down. However I am not convinced with my own explanation as I feel I am missing out on something. Please feel free to help me out.

$\endgroup$
  • $\begingroup$ I have updated your post with chemistry markup. If you want to know more, please have a look here and here. We prefer to not use MathJax in the title field, see here for details. $\endgroup$ – Martin - マーチン Apr 26 '17 at 7:30
  • $\begingroup$ Ahh, I was sumultaneously editing at the same time @Martin ! $\endgroup$ – Pritt says Reinstate Monica Apr 26 '17 at 7:36
1
$\begingroup$

Increasing $\ce{[E]}$ lowers $\ce{[C]}$ by a simple application of Le Chatelier's Principle. Regarding the effect of increasing $\ce{[E]}$ on $\ce{[A]}$, your understanding is correct. To make your observation more obvious, we may reverse reaction (ii) and add it to reaction (i): $$\ce{A(g) + E(g)<=>B(g) + D(g)}$$ So we can, once again, simply apply Le Chatelier's Principle and see that increasing $\ce{[E]}$ lowers $\ce{[A]}$.

$\endgroup$
  • $\begingroup$ But does the decrement of A inturn imply an increment in C as per equilibrium (i) ? $\endgroup$ – DIPANJAN Chowdhury Apr 26 '17 at 10:04
  • $\begingroup$ @DIPANJANChowdhury, no. Increasing $\ce{[A]}$ increases $\ce{[C]}$, as you've already stated in your post. $\endgroup$ – a-cyclohexane-molecule Apr 26 '17 at 14:44

Your Answer

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

Not the answer you're looking for? Browse other questions tagged or ask your own question.