Which of the following reactions has a positive change in entropy, ∆S?
a. CH₃Cl(g) + 3 Cl₂(g) → CCl₄(g) + 3 HCl(g)
b. SO₃(g) → SO₂(g) + 1/2 O₂(g)
c. Na(s) + 1/2 Cl₂(g) → NaCl(s)
d. 2 NH₃(g) → N₂(g) + 3 H₂(g)