NEET 2021 · ChemistryPrevious Year Question

Which of the following reactions is a metal displacement reaction? Choose the right option.

Answer: (D) (d) $Cr X_{2} O X_{3} + 2 Al Δ Al X_{2} O X_{3} + 2 Cr$ . \textbf{Answer:} (d) $Cr X_{2} O X_{3} + 2 Al Δ Al X_{2} O X_{3} + 2 Cr$ \textbf{Solution:} A metal displacement reaction is one in which a more reactive metal displaces a less reactive metal from its compound.

A.(a) $Fe + 2 HCl FeCl X_{2} + H X_{2} ↑$
B.(b) $2 Pb (NO X_{3}) X_{2} Δ 2 PbO + 4 NO X_{2} + O X_{2} ↑$
C.(c) $2 KClO X_{3} Δ 2 KCl + 3 O X_{2}$
D.(d) $Cr X_{2} O X_{3} + 2 Al Δ Al X_{2} O X_{3} + 2 Cr$ ✓

Correct Answer

(D) (d) $Cr X_{2} O X_{3} + 2 Al Δ Al X_{2} O X_{3} + 2 Cr$

Solution & Explanation

\textbf{Answer:} (d) $Cr X_{2} O X_{3} + 2 Al Δ Al X_{2} O X_{3} + 2 Cr$ \textbf{Solution:} A metal displacement reaction is one in which a more reactive metal displaces a less reactive metal from its compound. In $Cr X_{2} O X_{3} + 2 Al Al X_{2} O X_{3} + 2 Cr$ , the more reactive metal Al displaces Cr from $Cr X_{2} O X_{3}$ (the thermite reaction). Reaction (a) is hydrogen displacement, while (b) and (c) are thermal decomposition reactions. Hence the metal displacement reaction is (d).

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