Answer:
The balanced equation is: Zn(s) + 2H⁺(aq) → Zn²⁺(aq) + H₂(g)
Explanation:
Zn(s) is a simple substance (its oxidation number is zero) and it is oxidized to Zn²⁺. It loses two electrons, so the half reaction is the following:
Zn(s) → Zn²⁺(aq) + 2 e- (oxidation reaction)
Hydrogen ion (H⁺) is reduced to hydrogen gas (H₂). The oxidation number is decreased from +1 to 0 (because H₂ is a simple substance). H⁺ gains 1 electron per H atom, so the half reaction is the following:
2H⁺(aq) + 2 e- → H₂(g) (reduction reaction)
We obtain the overall reaction from the addition of the two half reactions. We write the reduction reaction first and then the oxidation reaction, as follows:
2H⁺(aq) + 2 e- → H₂(g)
+
Zn(s) → Zn²⁺(aq) + 2 e-
---------------------------------
Zn(s) + 2H⁺(aq) → Zn²⁺(aq) + H₂(g)
The two electrons at both sides of the equation (2 e-) are canceled. The overall reaction is in acidic solution due to the presence of H⁺ ions. The net charge at both sides is the same : +2, so the mass and the charge are balanced.
