Which of the following reactions shows work of compression?

Which of the following reactions shows work of compression?
  1. $\mathrm{NH}_{3(\mathrm{~g})}+\mathrm{HCl}(\mathrm{g}) \longrightarrow \mathrm{NH}_4 \mathrm{Cl}_{(\mathrm{s})}$
  2. $\mathrm{C}_2 \mathrm{H}_{6(\mathrm{~g})} \longrightarrow 2 \mathrm{C}_{(\mathrm{s})}+3 \mathrm{H}_{2(\mathrm{~g})}$
  3. $2 \mathrm{SO}_{3(\mathrm{~g})} \longrightarrow 2 \mathrm{SO}_{2(\mathrm{~g})}+\mathrm{O}_{2(\mathrm{~g})}$
  4. $2 \mathrm{H}_2 \mathrm{O}_{2(\ell)} \longrightarrow 2 \mathrm{H}_2 \mathrm{O}_{(\ell)}+\mathrm{O}_{2(\mathrm{~g})}$

Solution

$\mathrm{NH}_{3(\mathrm{~g})}+\mathrm{HCl}_{(\mathrm{g})} \longrightarrow \mathrm{NH}_4 \mathrm{Cl}_{(\mathrm{s})}$ In this reaction, gaseous reactant converted into solidified product which resulting in a decrease of volume and shows work of compression.

Asked in: MHT CET 2021 (20 Sep Shift 2)

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