We know that the equilibrium constant of a balanced chemical reaction

$$aA+bB \rightarrow cC+dD$$

is defined as $K_\mathrm{c}=\frac{[C]^c[D]^d}{[A]^a[B]^b}$. But if we multiply both the left hand side and right hand side of the reaction by $n$, the reaction is still the same and the reactants and products are still balanced.

$$(a \cdot n)A+(b \cdot n)B \rightarrow (c \cdot n)C+(d \cdot n)D$$

But then the equilibrium constant becomes

$$K_\mathrm{c}^\prime=\frac{[C]^{c \cdot n}[D]^{d \cdot n}}{[A]^{a \cdot n}[B]^{b \cdot n}},$$

which is different from the previous one. Which $K_\mathrm{c}$ is correct and how are we getting two different equilibrium constants of the same chemical reaction whereas we know equilibrium constant of a certain chemical reaction varies with temperature only?

  • 2
    $\begingroup$ The numerical value of the second $K_\mathrm{c}$ is different. If you use it with the equation it belongs to, you will find that makes no difference. $\endgroup$
    – Karl
    Sep 22 at 20:50
  • 1
    $\begingroup$ As Karl said, you have different values but you get the same results for the equilibrium ($Q$ is also defined differently). So the model is different, but the reality is the same. $\endgroup$
    – Karsten
    Sep 22 at 21:29
  • 1
    $\begingroup$ Even this seems kinda miss the point that equation is hardly determined by coefficients, just by actual mechanism. You don't multiply elementary reactions! $\endgroup$
    – Mithoron
    Sep 22 at 23:19
  • $\begingroup$ @Mithoron what did the first answer provider mean by smallest integer in stoichiometric equations?Does that mean a balanced stoichiometric reaction can only have natural numbers as coefficients and not fractional numbers? $\endgroup$
    – aquaman
    Sep 23 at 5:47


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