Question

In which of the following reactions the equilibrium constant will have no units?

• A. $NO\left(g\right)\rightleftharpoons \frac{1}{2}{N}_2\left(g\right)+\frac{1}{2}{O}_2\left(g\right)$
• B. $H_2\left(g\right)+l_2\left(g\right)\rightleftharpoons 2HI\left(g\right)$
• C. $CO\left(g\right)+H_{2}O\left(g\right)\rightleftharpoons C{O}_2\left(g\right)+H_2\left(g\right)$
• D. In all the above reactions

Answer 1

The correct option is D In all the above reactions

For a general reaction,
$aA+bB\to cC+dD$
Equilibrium constant is written as:
$\Rightarrow K_c=\frac{\left[C{]}^c\right[D{]}^d}{\left[A{]}^a\right[B{]}^b}$
so, whenever total moles of reactants and that of products are same i.e. ($\Delta n_g=0$) $K_c$ will not have units which here hold true for all the reactions (since all the species are in gaseous phase only).