Question

The correct expression of $K_c$ for $2HI\left(g\right)\rightleftharpoons H_2\left(g\right)+I_2\left(g\right)$ is

• A. $K_c=\frac{\left[H_2\right]\left[I_2\right]}{[HI{]}^2}$
• B. $K_c=\frac{\left[H_2\right]\left[I_2\right]}{2\left[HI\right]}$
• C. $K_c=\frac{[HI{]}^2}{\left[H_2\right]\left[I_2\right]}$
• D. $K_c=\frac{\left[HI\right]}{\left[H_2{]}^2\right[I_2{]}^2}$

Answer 1

The correct option is A $K_c=\frac{\left[H_2\right]\left[I_2\right]}{[HI{]}^2}$

The equilibrium constant of the reaction, $K_c$, is the ratio of the equilibrium concentrations of products over the equilibrium concentrations of reactants each raised to the power of their stoichiometric coefficients.
Thus, for reaction
$2HI\left(g\right)\rightleftharpoons H_2\left(g\right)+I_2\left(g\right)$

$K_c=\frac{\left[H_2\right]\left[I_2\right]}{[HI{]}^2}$