Question

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

• A. $2KClO_3 {->[\Delta]} 2KCl + 3O_2$
• B. $Cr_2O_3 + 2Al {->[\Delta]} Al_2O_3 + 2Cr$
• C. $Fe + 2HCl \to FeCl_2 + H_2 \uparrow$
• D. $2Pb(NO_3)_2 \to 2PbO + 4NO_2 + O_2 \uparrow$

Answer 1

The Correct Option is B

The question asks us to identify which of the given reactions is a metal displacement reaction. To solve this, we need to understand what a metal displacement reaction is.

A metal displacement reaction, also known as a single displacement or substitution reaction, involves one element being replaced by another in a compound. This typically occurs when a more reactive metal displaces a less reactive metal from its compound.

Let's analyze each option: 

1. \(2KClO_3 {->[\Delta]} 2KCl + 3O_2\)
   • This is a decomposition reaction where potassium chlorate decomposes into potassium chloride and oxygen gas. No displacement occurs here.
2. \(Cr_2O_3 + 2Al {->[\Delta]} Al_2O_3 + 2Cr\)
   • In this reaction, aluminum displaces chromium from chromium(III) oxide to form aluminum oxide and free chromium. Here, aluminum, a more reactive metal, displaces chromium. This is a metal displacement reaction.
3. \(Fe + 2HCl \to FeCl_2 + H_2 \uparrow\)
   • This is also a displacement reaction, but it is specifically an example of a reaction between a metal and an acid to produce a salt and hydrogen gas, not strictly a metal-for-metal displacement.
4. \(2Pb(NO_3)_2 \to 2PbO + 4NO_2 + O_2 \uparrow\)
   • This is a decomposition reaction where lead(II) nitrate decomposes to form lead(II) oxide, nitrogen dioxide, and oxygen. Again, no displacement of a metal occurs.

From the analysis, option 2, \(Cr_2O_3 + 2Al {->[\Delta]} Al_2O_3 + 2Cr\), is the correct answer as it demonstrates a metal displacement reaction where aluminum, being more reactive, displaces chromium from its oxide compound.