Enthelpy/Entropy question. Br2 liquid to 2Br gas

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SUMMARY

The reaction Br2 (l) to 2Br (g) involves an increase in entropy (S) and a decrease in enthalpy (H), making option B (H is negative and S is positive) the correct answer. The transition from liquid to gas results in more macrostates, confirming the positive change in entropy. The reaction is exothermic, releasing heat, which supports the negative enthalpy change. The confusion arises from the presence of option D, which is identical to B, leading to uncertainty regarding the teacher's intent.

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  • Understanding of thermodynamics concepts, specifically enthalpy and entropy.
  • Familiarity with the Gibbs free energy equation (dG = dH - TdS).
  • Knowledge of phase changes and their impact on molecular behavior.
  • Basic principles of exothermic and endothermic reactions.
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  • Study the Gibbs free energy and its implications in chemical reactions.
  • Explore the concepts of exothermic vs. endothermic reactions in detail.
  • Investigate phase transitions and their effects on entropy changes.
  • Review thermodynamic principles related to macrostates and microstates.
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Homework Statement


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

Homework Equations



dG= dH - TdS

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.
 
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Why do you say it's exothermic?
 

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