SPM Chemistry Form 5 Notes – Terminology and Concepts: Oxidation and Reduction (Part 10)

by BerryBerryTeacher

in Berry Reference (Notes)

As continuation to Part 9 featuring yet again the reactivity series, this part focuses on the position of hydrogen in the reactivity series of metal and what is the significance of the position. So the Berry Berry Teacher would like to highlight to all Berry Readers, Part 10 of the SPM Form 5 Chemistry notes on “Oxidation and Reduction” – position of hydrogen. Please read up Part 9 of this series of notes first if you have not done so, as you’ll find yourself missing a lot of crucial points if you were to start directly on this part. The tips to this SPM Chemistry Form 5 subchapter is to always remember the relative position of hydrogen on the reactivity series which is in between Zinc (Zn) and Iron (Fe). After that, try and understand the examples. If you can fully understand the examples, it means that you have grasp the concept and significance of the position of hydrogen in the series.

SPM Chemistry Form 5 – Terminology and Concepts: Oxidation and Reduction (Part 10)

Rusting of Iron Nails

Rusting of Iron Nails

Position of Hydrogen in the Reactivity Series of Metals

Reactivity Series
K, Na, Ca, Mg, Al, C, Zn, H, Fe, Sn, Pb, Cu, Hg, Ag, Au
<——– increase in reactivity

Metal oxide + Hydrogen –> Metal + Water

Any metal below hydrogen in the reactivity series, hydrogen will reduce the oxide of metal to metal.

Example 1:

  • CuO(s) + H2(g) –> Cu(s) + H2O(l)
  • Observation: Burns quickly with a bright flame. The black solid turns brown solid.
  • H2: Reducing agent
  • CuO: Oxidising agent
  • Hydrogen is more reactive than copper.

Example 2:

  • PbO(s) + H2(g) –> Pb(s) + H2O(l)
  • Observation: Burns with a bright flame. The yellow solid turns grey solid.
  • H2: Reducing agent
  • PbO: Oxidising agent
  • Hydrogen is more reactive than lead.

Example 3:

  • Fe2O3(s) + 3H2(g) –> 2Fe(s) + 3H2O(l)
  • Observation: Glows dimly. The reddish-brown solid turns grey solid.
  • H2: Reducing agent
  • Fe2O3: Oxidising agent
  • Hydrogen is more reactive than iron.

Example 4:

  • ZnO(s) + H2(g) –> no reaction
  • Observation: No glow is observed. It turns yellow when hot and white when cold.
  • Hydrogen is unable to reduce zinc oxide. Hydrogen is less reactive than zinc.

Next up in Part 11 of this series is the slightly (only marginally) difficult subtopic of redox reactions in an electrolytic cells and chemical cells.

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