In a reaction involving gray zinc metal and purple iodine crystals, what is the limiting reagent?

• A. Iodine.
• B. Zinc.
• C. Methanol.
• D. Ionide.

Answer: (A)

To determine the limiting reagent in a reaction involving gray zinc metal and purple iodine crystals, one must examine the stoichiometry of the reaction. A limiting reagent is the reactant that will be completely consumed first, thereby stopping the reaction.

In this case, zinc and iodine are both reactants. The balanced chemical equation for this reaction can be represented as:

[ \text{Zn (s)} + \text{I}_2 (s) \rightarrow \text{ZnI}_2 (s) ]

In this equation, one mole of zinc reacts with one mole of iodine. To identify the limiting reagent, one needs to compare the molar amounts of zinc and iodine that are available.

If the amount of iodine provided is less than that of zinc, then iodine will run out first, making it the limiting reagent. Conversely, if there is insufficient zinc compared to iodine, then zinc would be the limiting reagent.

If the conditions given in the problem indicate there is a stoichiometric excess of zinc compared to iodine, then iodine would indeed be the limiting reagent, as it would be fully consumed before zinc.

Therefore, this reasoning confirms that iodine is the limiting reagent in the reaction, indicative of its exhaustion being the factor that dictates the