(a) For the reaction,
\(\frac{1}{2}\)H2 (g) \(\frac{1}{2}\) I2 (g) ⇌ HI (g)
Kc = \(\frac{[HI]}{[H_2]^{\frac{1}{2}}[I_2]^{\frac{1}{2}}}\) = 5
And for the reaction,
2HI (g) ⇌ H2(g) + I2 (g)
Kc = \(\frac{[H_2][{I_2]}}{[HI]^2}\) = \(\big(\frac{1}{K_c}\big)^2\)
= \(\big(\frac{1}{5}\big)^2\) = \(\frac{1}{25}\) = 0.04
(b) The stage of equilibrium at which the rates of the forward and backward reactions become equal is called dynamic nature of equilibrium. Dynamic refers to anything having motion. Since, equilibrium is not static so it shows dynamic nature.