2. Which one of the following reactions has no work in terms of the system?

A) 2 NO 2(g)+ 7 H 2(g) -> 2 NH 3(g) + 4 H 2O(l)

B) PCl 5(g) -> PCl 3(g) + Cl 2(g)

C) Br 2(g) -> 2 Br(g)

D) 2 SO2(g) + O 2(g) -> 2 SO3(g)

E) N2(g) + O2(g) -> 2 NO(g)