Chemistry Regents Practice Test

What type of reaction is represented by the equation Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g)?

1. Synthesis

2. Decomposition

3. Single replacement

4. Double replacement

The correct answer is: Single replacement

The reaction represented by the equation Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g) is classified as a single replacement reaction. In this type of reaction, one element (in this case, zinc) displaces another element from a compound (the hydrogen ion from sulfuric acid). Zinc, a more reactive metal, reacts with sulfuric acid and replaces the hydrogen ions, resulting in the formation of zinc sulfate and hydrogen gas. This characteristic of having one element taking the place of another in a compound aligns perfectly with the defining features of a single replacement reaction. In contrast, synthesis reactions involve the combination of two or more substances to form a single compound, while decomposition reactions involve a single compound breaking down into two or more simpler products. Double replacement reactions typically involve the exchange of ions between two compounds, which does not occur in this case. Thus, the nature of the reactants and products confirms that it is indeed a single replacement reaction.