Question

In the reaction below, iodine gas, I2(g), is violet in color, while hydrogen gas, H₂(g), and hydrogen iodide, HI(g), are both colorless. When H₂(g) and I2(g) are combined in a closed flask, the violet gas never disappears completely. Which of the following explains this observation? H₂(g)+I2(g)→2HI(g)

a) The forward reaction, H₂(g)+I2(g)→2HI(g), is proceeding too slowly for any HI(g) to form.
b) The reverse reaction, 2HI(g)→H₂(g)+I2(g), is occurring at the same rate as the forward reaction.
c) The product of the original reaction is reacting with the (g), forming a gas with properties similar to I2(g).
d) The reaction has reached completion, and H₂(g) was the limiting reactant, leaving unreacted I2(g) behind.

Answer 1

The observation that the violet gas never disappears completely in the reaction is explained by option b) The reverse reaction, 2HI(g)→H₂(g)+I₂(g), occurring at the same rate as the forward reaction.

Step-by-step explanation:

The violet color of iodine gas remains visible because the reaction between iodine gas and hydrogen gas has reached chemical equilibrium, where the forward and reverse reactions occur at the same rate. The observation that the violet gas never disappears completely in the reaction between iodine gas (I₂(g)) and hydrogen gas (H₂(g)) is best explained by the reverse reaction, 2HI(g) → H₂(g) + I₂(g), is occurring at the same rate as the forward reaction.

This means that the reaction is dynamic and has reached a point of chemical equilibrium where the forward and reverse reactions proceed at equal rates, resulting in no net change in the concentration of reactants and products. This explains why the violet color of iodine gas remains visible.

Thus, the correct option is B.