Consider the following reactions: $\mathrm{H}_{2}(g)+\mathrm{I}_{2}(g) \rightleftharpoons 2 \mathrm{HI}(g) \quad\( and \)\quad \mathrm{H}_{2}(g)+\mathrm{I}_{2}(s) \rightleftharpoons 2 \mathrm{HI}(g)$ List two property differences between these two reactions that relate to equilibrium.

The reaction quotient (Q) is defined as the ratio of the concentrations of the products raised to their stoichiometric coefficients to the concentrations of the reactants raised to their stoichiometric coefficients. For the first reaction, the reaction quotient is given by: \[Q_1 = \frac{[\mathrm{HI}]^2}{[\mathrm{H}_2][\mathrm{I}_2]}\] At equilibrium, the reaction quotient (Q) becomes the equilibrium constant (K). Therefore, the equilibrium constant for the first reaction is: \[K_1 = \frac{[\mathrm{HI}]^2}{[\mathrm{H}_2][\mathrm{I}_2]}\] For the second reaction, the equilibrium expression is: \[Q_2 = \frac{[\mathrm{HI}]^2}{[\mathrm{H}_2]}\] Since the concentration of solid iodine (I2) does not affect the equilibrium, it is omitted from the equation. At equilibrium, the reaction quotient becomes the equilibrium constant: \[K_2 = \frac{[\mathrm{HI}]^2}{[\mathrm{H}_2]}\] Notice that the equilibrium constant expressions for the two reactions are different.

Le Chatelier's principle states that if a change in conditions is imposed on a system at equilibrium, the system will adjust itself in a way to counteract the change and restore equilibrium. For the first reaction, changes in pressure or volume will affect the equilibrium since all species involved are gases: \[\mathrm{H}_2(g) + \mathrm{I}_2(g) \rightleftharpoons 2 \mathrm{HI}(g)\] If the pressure increases or the volume decreases, the system will shift towards the side with fewer moles of gas, which is the side with the products (HI). Conversely, if the pressure decreases or the volume increases, the system will shift towards the side with more moles of gas, which is the side with the reactants (H2 and I2). For the second reaction, changes in pressure or volume will have no effect on the position of solid iodine in the equilibrium: \[\mathrm{H}_2(g) + \mathrm{I}_2(s) \rightleftharpoons 2 \mathrm{HI}(g)\] Since the concentration of solid iodine (I2) does not change with pressure or volume, only the gaseous reactant and product will be affected. Therefore, Le Chatelier's principle will have a different impact on the second reaction compared to the first one. In summary, the two property differences between these reactions related to equilibrium are: 1. Differences in their equilibrium constant expressions due to the state of iodine (gaseous in the first reaction and solid in the second reaction). 2. Differences in the effect of pressure or volume changes due to the different participation of gaseous and solid species in the reactions, according to Le Chatelier's principle.