quick MCAT problem...can't figure answer

[ronaldo23]

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got it thanks

 

[adamber]

C?

 

[Waterlilies]

c 🙂

 

[ronaldo23]

why?

 

[adamber]

A cannot be correct, because the second law of thermo is never violated. D is incorrect, because deltaG= deltaH- TdeltaS, and delta S is decreasing, so overall it will be positive deltaG, which is non-spontaneous. B is backwards, because if the entropy of the system is decreasing, then the entropy of the surrounding must be increasing, since that maintains the second law of thermo.

 

[biggiesmallsiz]

why?

evaporation = lots of gas molecules = lots of entropy adding to the universe

 

[SketchLazy]

When dissolved sugar is recrystallized by evaporating the water, its entropy decreases. A crystal is more ordered than particles in solution. In terms of thermodynamics, this must mean that

A the second law of thermodynamics is broken.
B the entropy of some other part of the system is increased.
C the entropy of the universe is increased.
D evaporation will occur spontaneously.

I think it's B. The water that is dissolving the sugar is also part of the system. When it evaporates, its entropy increases because it is becoming a gas.

 

[biggiesmallsiz]

I think it's B. The water that is dissolving the sugar is also part of the system. When it evaporates, its entropy increases because it is becoming a gas.

its def C jesus christ. do you have the answer?

 

[adamber]

I think it's B. The water that is dissolving the sugar is also part of the system. When it evaporates, its entropy increases because it is becoming a gas.

The water is part of the system originally, but when it evaporates, the gas molecules contribute to the entropy of the surroundings by spreading out further.

 

[Revilla]

Another vote for C here.