Question

Consider the half reactions below for a chemical reaction.

2 Equations: First: upper M g right arrow upper M g superscript 2 plus (a q) plus 2 e superscript minus. Second: 2 upper H superscript plus (a q) plus 2 superscript plus right arrow upper H subscript 2 (g).

What is the overall equation for this chemical reaction?
Upper M g (s) plus 2 upper H superscript plus (a q) right arrow upper M g superscript 2 plus (a q) plus upper H subscript 2 (g).
Upper M g (s) plus 2 upper H superscript plus (a q) right arrow upper M g superscript 2 plus (a q) plus 2 e superscript minus.
Upper M g superscript 2 plus (a q) plus upper H subscript 2 (g) right arrow upper M g (s) plus 2 upper H superscript plus (a q).
Upper M g (s) plus 2 upper H right arrow upper M g (a q) plus upper H subscript 2 (g).

Answer 1

Add the two half‑reactions and cancel the electrons:

Mg(s) → Mg2+(aq) + 2 e−
2 H+(aq) + 2 e− → H2(g)

Overall: Mg(s) + 2 H+(aq) → Mg2+(aq) + H2(g)

(Option 1).