Questions: Oxidation-Reduction Reactions: Electron Transfer
3 questions to test your understanding
Score: 0 / 3
Question 1 Multiple Choice
In the reaction Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s), zinc is oxidized. Which species is the oxidizing agent?
AZinc (Zn), because it loses electrons
BZinc sulfate (ZnSO₄), because it is the ionic product
CCopper(II) ion (Cu²⁺), because it gains the electrons that zinc loses
DSulfate ion (SO₄²⁻), because it stabilizes the zinc cation
The oxidizing agent is the species that causes oxidation in another substance — it does so by accepting electrons itself, and therefore gets reduced. Cu²⁺ gains two electrons (Cu²⁺ + 2e⁻ → Cu) and is therefore the oxidizing agent. Zinc loses electrons and is oxidized — making zinc the reducing agent. The agent and the species undergoing the change are always different.
Question 2 True / False
The oxidizing agent in a redox reaction is the species that loses electrons.
TTrue
FFalse
Answer: False
This is the single most common redox misconception. The oxidizing agent GAINS electrons (is itself reduced) — it causes oxidation in the other reactant by pulling away electrons. The REDUCING agent loses electrons (is itself oxidized). Memory device: OIL RIG — Oxidation Is Loss, Reduction Is Gain. The agent terminology always refers to what the species does TO the other reactant, not what happens to itself... except in reverse.
Question 3 Short Answer
Assign oxidation numbers to all atoms in the reaction 2H₂ + O₂ → 2H₂O, and identify which element is oxidized and which is reduced.
Think about your answer, then reveal below.
Model answer: In H₂: H = 0. In O₂: O = 0. In H₂O: H = +1, O = -2. Hydrogen goes from 0 to +1 (loses electrons — oxidized). Oxygen goes from 0 to -2 (gains electrons — reduced). H₂ is the reducing agent; O₂ is the oxidizing agent.
Elements in their pure elemental form always have an oxidation number of 0. In H₂O, oxygen's oxidation number is -2 (its most common value) and hydrogen is +1. Tracking the change in oxidation number is how you identify oxidation (increase) and reduction (decrease) without explicitly tracking electron movement.