Wave "B" is thinner. Is this the whole question?
Answer:
The reducing agent is Zn.
Explanation:
Let's consider the reaction between zinc and hydrochloric acid.
Zn(s) + 2 HCl(aq) ⇄ ZnCl₂(aq) + H₂(g)
This is a redox reaction, which can be divided in 2 half-reactions: reduction and oxidation.
In the reduction, H⁺ gains electrons and it is considered the oxidizing agent.
2H⁺ + 2 e⁻ ⇒ H₂
In the oxidation, Zn loses electrons and it is considered the reducing agent.
Zn ⇒ Zn²⁺ + 2 e⁻
The correct answer to the question is 25 percent by mass
