Which one of the following is the correct arrangement of metals in the decreasing order of their reactivity?
- (a)Iron, Sodium, Silver, Copper
- (b)Silver, Copper, Iron, Sodium
- (c)Sodium, Copper, Silver, Iron
- (d)Sodium, Iron, Copper, Silver
Correct — D, Sodium, Iron, Copper, Silver. In the reactivity (activity) series, sodium is highly reactive, iron is moderately reactive, and copper and silver are unreactive noble metals, so the decreasing order of reactivity is Na > Fe > Cu > Ag. Option D lists exactly this sequence.
- (a)Iron, Sodium, Silver, Copper — Sodium is far more reactive than iron, so Na must come before Fe; also copper is more reactive than silver, not less, so silver cannot precede copper.
- (b)Silver, Copper, Iron, Sodium — This is the increasing order of reactivity (least to most reactive) — the reverse of what the question asks.
- (c)Sodium, Copper, Silver, Iron — Iron is more reactive than copper and silver, so it cannot be placed last; iron belongs just after sodium.
The reactivity series ranks metals by how readily they lose electrons and take part in reactions. Highly reactive metals like sodium react even with cold water, moderately reactive metals like iron react slowly, and the least reactive noble metals like copper and silver resist reaction. A more reactive metal can displace a less reactive one from its salt solution.
To order the four metals, recall the standard series: sodium sits high up, iron in the middle, and copper and silver near the bottom just above gold. Reading from most to least reactive gives Na, Fe, Cu, Ag directly.
- A common activity series runs K > Na > Ca > Mg > Al > Zn > Fe > Pb > (H) > Cu > Ag > Au.
- A more reactive metal displaces a less reactive one from its salt solution.
- Sodium reacts vigorously with water; iron reacts only slowly; copper and silver do not react with water.
- Silver and gold are noble metals, often found native and highly unreactive.
Decreasing reactivity: sodium, then iron, then copper, then silver.
- Giving the increasing order when decreasing is asked.
- Misplacing iron as less reactive than copper or silver.
NDA/UPSC ask you to order metals by reactivity or to predict which metal displaces another — anchor it to the standard activity series.
No directly related past PYQ was found.
- practice — not a real PYQ
Which of the following metals is the most reactive?
- (a)Copper
- (b)Silver
- (c)Sodium
- (d)Gold
Answer(c) Sodium — it sits high in the reactivity series and reacts even with cold water.
- practice — not a real PYQ
An iron nail dipped in copper sulphate solution turns brownish because
- (a)copper is more reactive than iron
- (b)iron is more reactive and displaces copper
- (c)no reaction occurs
- (d)iron dissolves in water
Answer(b) iron is more reactive and displaces copper — iron pushes copper out of the solution, depositing copper on the nail.