At constant pressure, which of these systems do work on the surroundings? 2A(g)+2B(g)⟶3C(g) , A(g)+B(g)⟶3C(g) , A(s)+B(s)⟶C(g), 2A(g)+3B(g)⟶4C(g)

Answer 1

Which of the systems has more moles of gas on the product side than on the reactant side? If that were the case, in order to maintain constant pressure, the volume would have to increase and that would mean the system was doing work on the surrounding.

Looks like it would be A(g) + B(g) ==> 3C(g) where 2 moles of gas on the reactant side turn into 3 moles of gas on the product side.