Question

the reaction represented by the equation \\(\text{mg(s)} + 2\text{hcl(aq)} \
ightarrow \text{h}_2\text{(g)} + \text{mgcl}_2\text{(aq)}\\) is a

a. composition reaction.
b. decomposition reaction.
c. single-displacement reaction.
d. double-displacement reaction.

Explanation:

Analyze the chemical equation structure

$$ \text{Mg}(s) + 2\text{HCl}(aq) ightarrow \text{H}_2(g) + \text{MgCl}_2(aq) $$

This reaction follows the general form:

$$ \text{A} + \text{BC} ightarrow \text{B} + \text{AC} $$

Identify the reaction type

The free element magnesium (\(\text{Mg}\)) replaces the hydrogen (\(\text{H}\)) in hydrochloric acid (\(\text{HCl}\)), releasing hydrogen gas and forming magnesium chloride. This represents a single-displacement (or single-replacement) reaction.

Answer:

• a. composition reaction.
• b. decomposition reaction.
• c. single-displacement reaction. (Correct answer)
• d. double-displacement reaction.