Study Guides/Chemistry/Why Cannot Each Metal React to Its Own Salt?
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Why Cannot Each Metal React with Its Own Salt Solution?

A metal cannot react with a solution of its own salt because a displacement reaction only occurs when a more reactive metal displaces a less reactive metal from its salt solution. Since a metal cannot be more reactive than itself, no displacement takes place. For example, iron cannot displace iron from iron sulphate solution — there is no net reaction.

Question (Click to Flip)

Why cannot each metal react to its own salt solution?

Answer

A metal cannot react with its own salt solution because a displacement reaction requires a more reactive metal to displace a less reactive one. Since a metal cannot be more reactive than itself, there is no driving force. The net ionic equation becomes identical on both sides: M + M²⁺ → M²⁺ + M — no observable change.

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Key Facts

A metal cannot react with a solution of its own salt — no displacement occurs.

Displacement happens only when a more reactive metal meets the salt of a less reactive metal.

A metal cannot be more reactive than itself, so no driving force exists.

The net ionic equation for a metal with its own salt is identical on both sides.

Activity series determines which metal displaces which: higher metal displaces lower.

Example: Fe displaces Cu from CuSO₄, but Fe cannot displace Fe from FeSO₄.

The electrode potential difference is zero when a metal meets its own salt solution.

The Rule: Displacement Reactions

A metal displaces another metal from its salt solution only if the first metal is higher (more reactive) in the activity series:

More reactive metal + Salt of less reactive metal → Salt of more reactive metal + Less reactive metal

Example: Fe + CuSO₄ → FeSO₄ + Cu (iron is more reactive than copper)

For a metal to react with its own salt: Fe + FeSO₄ → ?

This reaction does not occur because iron cannot be more reactive than itself — there is no driving force for the reaction. The same applies to all metals with their own salts.

Activity Series and Its Role

The activity series (reactivity series) ranks metals from most reactive to least reactive:

K > Na > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > H > Cu > Ag > Au

Rule for displacement: • A metal can displace only those metals that are BELOW it in the series. • A metal CANNOT displace itself — it is neither above nor below itself. • Therefore, no metal can react with its own salt solution.

Examples: • Zn + CuSO₄ → ZnSO₄ + Cu ✓ (Zn is above Cu) • Cu + ZnSO₄ → No reaction ✗ (Cu is below Zn) • Zn + ZnSO₄ → No reaction ✗ (same metal)

Why No Reaction Occurs

The reason no metal reacts with its own salt solution:

  1. Thermodynamic reason — the reaction Fe → Fe²⁺ and Fe²⁺ → Fe occurring simultaneously means no overall change in energy — no driving force.

  2. Electrochemical reason — for a displacement reaction, there must be a difference in electrode potentials. A metal and its own ion have zero potential difference (same element), so no reaction occurs.

  3. Equilibrium reason — the reaction A + A²⁺ → A²⁺ + A is in equilibrium from the start. The forward and reverse reactions are identical, so there is no observable change.

Conclusion: The net ionic equation would be: M(s) + M²⁺(aq) → M²⁺(aq) + M(s) — identical on both sides, so no reaction.

Questions and Answers

Why cannot each metal react to its own salt solution?+

A metal cannot react with its own salt solution because a displacement reaction requires a more reactive metal to displace a less reactive one. Since a metal cannot be more reactive than itself, there is no driving force. The net ionic equation becomes identical on both sides: M + M²⁺ → M²⁺ + M — no observable change.

Can iron react with iron sulphate solution?+

No. Iron cannot displace iron from iron sulphate solution because displacement requires the displacing metal to be more reactive than the metal in the salt. Iron cannot be more reactive than itself, so no reaction occurs: Fe + FeSO₄ → No reaction.

What is the condition for a displacement reaction?+

A displacement reaction occurs when a more reactive metal is placed in the salt solution of a less reactive metal. The more reactive metal displaces the less reactive one from its salt. This is determined by the activity series of metals.

Give an example of a metal that can and cannot displace another metal.+

Zinc (Zn) CAN displace copper from CuSO₄ because Zn is above Cu in the activity series: Zn + CuSO₄ → ZnSO₄ + Cu. But Zn CANNOT react with ZnSO₄ (its own salt) because no metal can displace itself.

What is the activity series of metals?+

The activity series ranks metals from most to least reactive: K > Na > Ca > Mg > Al > Zn > Fe > Ni > Sn > Pb > H > Cu > Ag > Au. A metal can displace only those below it in this series from their salt solutions.

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