Question

Can reactions be forced to run backwards?

Answer 1

Chemical reactions:

1. A chemical reaction is a process that leads to the chemical transformation of one set of chemicals into other.
2. In a chemical reaction, the reactants change into products and if products react together they cannot form reactants.
3. For example: in the reaction, ${\mathrm{CH}}_4\left(\mathrm{g}\right)+2{\mathrm{O}}_2\left(\mathrm{g}\right)\to {\mathrm{CO}}_2\left(\mathrm{g}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right)$.
4. In the above reaction ${\mathrm{CH}}_4$ and ${\mathrm{O}}_2$ combine to form ${\mathrm{CO}}_2$ and ${\mathrm{H}}_2\mathrm{O}$.
5. But, ${\mathrm{CO}}_2$ and ${\mathrm{H}}_2\mathrm{O}$ will not react to form ${\mathrm{CH}}_4$ and ${\mathrm{O}}_2$.
6. Hence, in this case, reactions cannot be forced to run backwards.
7. In equilibrium, the rate of forward reaction is equal to the rate of backward reaction. Therefore, the reaction can go backwards to give back the reactants, for example:
8. ${\mathrm{N}}_2+3{\mathrm{H}}_2\rightleftharpoons 2{\mathrm{NH}}_3$
9. In this reaction, nitrogen and hydrogen react to form ammonia. This reaction can also go backwards to give back the reactants which are hydrogen and nitrogen.
10. Hence, reactions can go backwards.