Homework Help: Enthalpy/Entropy question. Br2 liquid to 2Br gas

1. Nov 9, 2009

Pr0x1mo

1. The problem statement, all variables and given/known data
Br2 (l) --> 2Br (g)

the options are:

a. H is positive and S is positive for the reaction
b. H is negative and S is positive for the reaction
c. H is positive and S is negative for the reaction
d. H is negative and S is positive for the reaction
e. G Is positive for all temperatures

2. Relevant equations

dG= dH - TdS

3. The attempt at a solution

The chemical reaction is going from liquid to gas, therefore the entropy is increasing because the reaction is causing more macrostates due to the greater area of distribution for the gas molecules. The reaction is exothermic, because its giving off heat.

Therefore, Entropy is increasing (S is positive) and since no heat is being absorbed Enthalpy is decreasing (H is negative).

So my answer is B.... so here's the dilemma,, B is the same answer as D. I don't know if this was a mistake on the teachers part, or I AM WRONG, and she put the answer there 2x to hint that its not the answer.

2. Nov 9, 2009

Mapes

Why do you say it's exothermic?