Reactivity of Metals (C4.1)
Reactivity series
Metals arranged in decreasing order of reactivity:
K > Na > Li > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > (H) > Cu > Ag > Au > Pt
More reactive metals react more readily with water, acids and oxygen.
Reactions with water
- Potassium, sodium, lithium: react vigorously with cold water → metal hydroxide + hydrogen.
2Na + 2H₂O → 2NaOH + H₂ - Calcium: reacts slowly with cold water.
- Magnesium: reacts only with steam, not cold water.
- Zinc, iron: do not react with cold water or steam under normal conditions.
- Copper and below: no reaction with water.
Reactions with dilute acid
More reactive metals react with dilute acid → salt + hydrogen:
Mg + 2HCl → MgCl₂ + H₂
Zn + H₂SO₄ → ZnSO₄ + H₂
Copper and below: no reaction with dilute acid.
Displacement reactions
A more reactive metal can displace (push out) a less reactive metal from its salt solution.
Example: Fe + CuSO₄ → FeSO₄ + Cu (iron is more reactive than copper)
Observation: iron nail placed in blue copper sulfate solution → turns brown (copper deposits); solution fades to pale green (iron(II) sulfate).
Extraction of metals
- Metals less reactive than carbon (copper, iron below carbon in the extended series, tin, lead): extracted by reduction with carbon/coke in a blast furnace.
Fe₂O₃ + 3CO → 2Fe + 3CO₂ - Metals more reactive than carbon (aluminium, magnesium, sodium, potassium): extracted by electrolysis of molten ore/compound (expensive).
- Gold: found native (as pure metal) in the Earth — no extraction needed.
Oxidation and reduction (OIL RIG)
- Oxidation = loss of electrons (or gain of oxygen)
- Reduction = gain of electrons (or loss of oxygen)
- OIL RIG: Oxidation Is Loss, Reduction Is Gain (of electrons)
In the blast furnace:
Fe₂O₃ is reduced (loses oxygen/gains electrons) → Fe
C is oxidised (gains oxygen) → CO₂
Redox reactions involve simultaneous oxidation and reduction.
Common exam errors
- Saying aluminium is extracted by reduction with carbon — it's more reactive than carbon → requires electrolysis.
- Forgetting that displacement requires the displacing metal to be more reactive.
- Confusing oxidation (loss of electrons) with reduction (gain of electrons) — use OIL RIG.
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