Question

In what reaction of the following, work is done by the system on the surroundings?
(a) Hg (l) → Hg (g)
(b) 3O₂ (g) → 2O₃ (g)
(c) H₂ (g) + Cl₂ (g) → 2HCl (g)
(d) N₂ (g) + 3H₂ (g) → 2NH₃ (g)

Answer 1

(a) Hg(l) → Hg(g)

For a chemical reaction, work is said to be done by the system on the surroundings when the number of moles of gaseous products is greater than the number of gaseous reactants. In the given reaction, reactant side does not have any gaseous reactants while product side has gaseous products. Thus, for the given reaction, work is done by the system on the surroundings