Positive Delta S: H2 + I2 --> 2HI, N2O4 from NO2

[enigmatic]

Question: Which of the following would probably have a positive delta S value?

He (g, 2atm) --> He (g, 10 atm)
H₂(g) + I₂(s) --> 2HI (g)
2Ag(s) + Br₂(l) --> 2AgBr(s)
O₂(g) --> O₂(aq)
2NO₂(g) --> N₂O₄(g)

My answer:
Well, I know that when a gas is pressurized, there are less states it can be in, so the first one's out.
I know that when a liquid becomes a solid, there are less possible states it can be in, so the third one's out.
I know that when a gas becomes an aqueous solution, there are less possible states it can be in, so the fourth one's out.

That leaves the second and fifth ones.
Can someone explain this to me?

 

[chemisttree]

The fifth one has two molecules reacting to form one molecule.

The second one has two molecules that are diatomic becoming two molecules that are composed of different species.