Select the correct statements from the following.

I. All the metals are same in reactivity.

II. Iron can replace copper from copper sulphate solution.

III. Copper can replace iron from ferrous sulphate solution.

IV. Sodium is too soft to cut with a knife.

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AAI Junior Assistant (Fire Service) Official Paper (Held On: 21 Apr, 2025 Shift 1)
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  1. Only I, II and IV
  2. Only I and II 
  3. Only II and IV
  4. Only II and III

Answer (Detailed Solution Below)

Option 3 : Only II and IV
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Detailed Solution

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The correct answer is Only II and IV.

Key Points

  • Statement II: Iron can replace copper from copper sulphate solution because iron is more reactive than copper. This is based on the reactivity series of metals.
  • Statement IV: Sodium is a highly reactive alkali metal that is soft and can be easily cut with a knife due to its low density and metallic bonding.
  • Statement I is incorrect: All metals do not have the same reactivity. The reactivity of metals varies and is arranged in the reactivity series.
  • Statement III is incorrect: Copper cannot replace iron from ferrous sulphate solution because copper is less reactive than iron.

Additional Information

  • Reactivity Series: A list of metals arranged in order of their decreasing reactivity. Highly reactive metals like sodium and potassium are at the top, while less reactive metals like gold and silver are at the bottom.
  • Displacement Reaction: A chemical reaction in which a more reactive metal displaces a less reactive metal from its compound (e.g., iron displaces copper from copper sulphate).
  • Properties of Sodium: Sodium is an alkali metal with low melting point and density. It reacts vigorously with water and oxygen, and it is so soft that it can be cut with a knife.
  • Metal Reactivity: Reactivity of a metal determines its ability to lose electrons and form positive ions. Highly reactive metals like alkali metals react easily, while noble metals like gold and platinum are least reactive.
  • Chemical Behavior of Copper: Copper is a less reactive metal and cannot displace more reactive metals such as iron from their compounds.
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Last updated on Apr 24, 2025

-> The AAI Junior Assistant Response Sheet 2025 has been out on the official portal for the written examination.

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