Question

Classify each of the following reactions:

(i) Ca (s) + PbCl2 (aq) -------> Pb(s) + CaCl2(aq)

(ii) MgCO3 --------> MgO + CO2

(i) is Single displacement and (ii) is decomposition reaction

Both (i) & (ii) are combination reaction

Both (i) and (ii) are decomposition reaction

(i) is Single displacement and (ii) is double displacement reaction.

Answer 1

(i)

Here, the element Ca is displacing Pb in the compound PbCl₂ to form CaCl₂.

Hence, only a single displacement of Pb by Ca is occurring.

Hence, (i) is a single displacement reaction.

(ii)

Here a single compound(MgCO₃) is being broken down into two different compounds (MgO and CO₂).

Hence, clearly (ii) is a decomposition reaction.

Hence, the correct choice is the first option:

(i) is single displacement and (ii) is decomposition reaction.

Note:

Second option is incorrect since none of the given reaction are combination reactions which involves combining of two or more compounds or elements to form a single compound.

Third option is incorrect since only reaction (ii) is decomposition reaction but (i) is a single displacement reaction.

Fourth option is incorrect since (ii) is not a double displacement reaction. In a double displacement reaction two compounds undergo cation and anion exchange among themselves having the following general form .