Question

consider the half reactions below for a chemical reaction.
mg ⟶ mg²⁺(aq) + 2e⁻
2h⁺(aq) + 2e⁻ ⟶ h₂(g)
what is the overall equation for this chemical reaction?
○ mg(s) + 2h⁺(aq) ⟶ mg²⁺(aq) + h₂(g)
○ mg(s) + 2h⁺(aq) ⟶ mg²⁺(aq) + 2e⁻
○ mg²⁺(aq) + h₂(g) ⟶ mg(s) + 2h⁺(aq)
○ mg(s) + 2h⁻ ⟶ mg(aq) + h₂(g)

Explanation:

Step1: Identify the two half - reactions

The first half - reaction is \( \text{Mg}(s)
ightarrow\text{Mg}^{2 + }(aq)+2e^- \) and the second half - reaction is \( 2\text{H}^+(aq)+2e^-
ightarrow\text{H}_2(g) \).

Step2: Add the two half - reactions together

When we add the two half - reactions, the electrons (\(2e^-\)) on the product side of the first reaction and the reactant side of the second reaction will cancel out.
Adding \( \text{Mg}(s)
ightarrow\text{Mg}^{2 + }(aq)+2e^- \) and \( 2\text{H}^+(aq)+2e^-
ightarrow\text{H}_2(g) \) gives:
\( \text{Mg}(s)+2\text{H}^+(aq)+2e^-
ightarrow\text{Mg}^{2 + }(aq)+2e^-+\text{H}_2(g) \)
After canceling the \(2e^-\) terms, we get \( \text{Mg}(s)+2\text{H}^+(aq)
ightarrow\text{Mg}^{2 + }(aq)+\text{H}_2(g) \)

Answer:

\(\text{Mg}(s) + 2\text{H}^+(aq)
ightarrow\text{Mg}^{2+}(aq)+\text{H}_2(g)\) (corresponding to the first option among the given choices)