SPM Chemistry Form 5 Notes – Terminology and Concepts: Oxidation and Reduction (Part 9)

by BerryBerryTeacher

in Berry Reference (Notes)

The reactivity of metals and its application in SPM Form 5 Chemistry level is usually regarded as a difficult topic by half of the students and easy topic by the other half. So today, the Berry Berry Teacher will like to share the secret to this subtopic with all Berry Readers, Part 9 of the SPM Form 5 Chemistry notes on “Oxidation and Reduction”. For those who find this subtopic easy, you won’t need this secret. For those who find it hard, then the secret is so simple that you would be disappointed with the revelation of it. To master this topic, all you really need is to just understand it rather than memorising it. With understanding, you can easily memorise this part because they all have logical links. So, before you start to read this post, it will be good to refresh the whole topic from Part 1-8.

SPM Chemistry Form 5 – Terminology and Concepts: Oxidation and Reduction (Part 9)

Rusting of Iron Nails

Rusting of Iron Nails

The Reactivity Series of Metals and Its Application

1. Metal form metal oxides when burnt in air (excess).
Metal + Oxygen –> Metal oxide
Example: 2Zn(s) + O2(g) –> 2ZnO(s)

2. The more reactive a metal is, the more vigorously it burns in oxygen.

Reactivity of Metals
K, Na, Ca, Mg, Al, Zn, Fe, Sn, Pb, Cu, Hg, Ag, Au
<——– increase in reactivity of metals

3. Reactivity of Metals with Oxygen.

Metal Observation Inference Equation
Magnesium (Mg) Burns vigorously with a very brilliant white flame.The residue is white when hot and cold. The reactivity of Mg towards O2 is very high.Magnesium oxide is formed. 2Mg(s) + O2(g)–> 2MgO(s)
Zinc (Zn) Burns quickly with a bright flame.The residue is yellow when hot and white when cold. The reactivity of Zn towards O2 is high.Zinc oxide is formed. 2Zn(s) + O2(g)–> 2ZnO(s)
Iron (Fe) Glows very brightly.The residue is reddish-brown when hot and cold. The reactivity of Fe towards O2 is medium.Iron(III) oxide is formed. 2Fe(s) + O2(g)–> 2Fe2O3(s)
Lead (Pb) Glows brightly.The residue is brown when hot and yellow when cold. The reactivity of Pb towards O2 is low.Lead(II) oxide is formed. 2Pb(s) + O2(g)–> 2PbO(s)
Copper (Cu) Glows faintly.The residue is black when hot and cold. The reactivity of Cu towards O2 is very low.Copper(II) oxide is formed. 2Cu(s) + O2(g)–> 2CuO(s)
  • Glass wool – prevents metal powder mixes with potassium manganate(VII)
  • Solid potassium manganate(VII) – liberates oxygen gas when it is heated / decomposed.

2KMnO4(s) —-> K2MnO4(s) + MnO2(s) + O2(g)
heat

  • Other than potassium manganate(VII),

- solid potassium chlorate(V) with manganese(IV) oxide as a catalyst.

MnO2
2KClO3(s) —-> KCl(s) + 3O2(g)
heat

- solid potassium nitrate

2KNO3(s) —-> KNO2(s) + O2(g)
heat

4. Position of Carbon in the Reactivity Series of Metals

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

a) Metal + Carbon dioxide –> Metal oxide + Carbon

Any metal above carbon in the reactivity series can displace oxygen from carbon dioxide.

Example: 2Mg(s) + CO2(g) –> 2MgO(s) + C(s)

Mg: Reducing agent
CO2: Oxidising agent
MgO: White residue
C: Black spots

–> Therefore, magnesium is more reactive than carbon.
(If the metal is less reactive than carbon, the metal is unable to remove oxygen from carbon dioxide.)

b) Carbon + Metal oxide –> Carbon dioxide + Metal

Any metal below carbon in the reactivity series can displace carbon from its oxide.

Example: C(s) + 2ZnO(s) –> 2Zn(s) + CO2(g)

C: Reducing agent
ZnO: Oxidising agent
Zn: Grey residue

–> Therefore, zinc is less reactive than carbon.
(If carbon is less reactive than the metal, the carbon is unable to remove oxygen from metal oxide.)

Next up in this series, is the position of hydrogen and how it is used as a baseline for comparison. So stay tune and log in frequently to BerryBerryEasy

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