Oxidation and reduction: losing and gaining electrons

Answer Key - Grade 10 Science Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   Nitrate, NO₃⁻, has charge -1, and each of its 3 oxygen atoms is -2. What is nitrogen's oxidation number, Bo?

   5
2. 2.

   Carbonate, CO₃²⁻, has charge -2, and each of its 3 oxygen atoms is -2. What is carbon's oxidation number, Esme?

   4
3. 3.

   In Zn + Cu²⁺ → Zn²⁺ + Cu, which is the oxidizing agent, Kira?

   • Cu²⁺
   • Zn
   • Cu
4. 4.

   In 2 Na + Cl₂ → 2 NaCl, which substance is reduced, Luz?

   • Sodium
   • Neither
   • Chlorine
5. 5.

   Milo says oxidation can happen only when oxygen takes part. Agree or disagree?

   • Disagree: it means losing electrons
   • Agree: the word comes from oxygen
   • Agree: rusting is what oxidation means
6. 6.

   Noah says sodium isn't oxidized in 2 Na + Cl₂ → 2 NaCl because there is no oxygen. Agree or disagree?

   • Disagree: Na loses an electron
   • Agree: oxidation needs oxygen to happen
   • Agree: sodium gains an electron
7. 7.

   Pia says a particle that gains electrons is oxidized. Agree or disagree?

   • Agree: its oxidation number goes up
   • Disagree: gaining is reduction
   • Agree: gaining electrons is oxidation
8. 8.

   Which half-reaction shows oxidation, Ren?

   • Zn²⁺ + 2e⁻ → Zn
   • Cu²⁺ + 2e⁻ → Cu
   • Zn → Zn²⁺ + 2e⁻
9. 9.

   Which half-reaction shows chlorine being reduced, Tala?

   • Cl₂ → 2 Cl⁻ + 2e⁻
   • Cl₂ → 2 Cl⁺ + 2e⁻
   • Cl₂ + 2e⁻ → 2 Cl⁻
10. 10.

    In 2 Al + 3 Cu²⁺ → 2 Al³⁺ + 3 Cu, how many electrons move in all, Zee?

    • 5
    • 6
    • 3