Explanation:
When H2 and I2 are mixed, they react to form HI according to the following balanced chemical equation:
H2(g) + I2(g) ⇌ 2HI(g)
In this reaction, the forward reaction is the formation of HI from H2 and I2, and the reverse reaction is the dissociation of HI into H2 and I2.

At equilibrium, the forward and reverse reactions occur at the same rate, which means that the rate of formation of HI is equal to the rate of dissociation of HI.

a) Amount of HI formed is equal to the amount of H2 dissociated: This statement is incorrect because at equilibrium, the amounts of HI, H2, and I2 will not necessarily be equal. The equilibrium constant for this reaction, Kc, is determined by the ratio of the concentrations of the products (HI) to the concentrations of the reactants (H2 and I2). Therefore, the amounts of products and reactants will depend on the initial concentrations and the value of the equilibrium constant.

b) HI dissociation stops: This statement is incorrect because at equilibrium, both the forward and reverse reactions are still occurring, just at the same rate. So, while the dissociation of HI is happening, it is being balanced by the formation of HI.

c) The reaction stops completely: This statement is incorrect because equilibrium is a dynamic state where both the forward and reverse reactions are happening. The reaction does not stop completely at equilibrium; it just reaches a point where the rates of the forward and reverse reactions are equal.

d) None of these: This is the correct answer because none of the statements accurately describe what happens at equilibrium.

In summary, at equilibrium, the formation of HI is balanced by the dissociation of HI, and the reaction does not stop completely. The amounts of reactants and products will depend on the initial concentrations and the equilibrium constant.