5 consider the sublimation of dry ice (solid carbon dioxide) at 25C: CO2(s) -> C

Question

5 consider the sublimation of dry ice (solid carbon dioxide) at 25C: CO2(s) -> CO2(g) 24)Imagine that your friend takes a piece of dry ice (solid carbon dioxide) out of the freezer and puts it in a beaker on the counter in the laboratory. A half an hour later when she comes back to the lab she sees that there is no longer any dry ice in her beaker. Which of the following statements about the sublimation of dry ice are correct?

a. The sublimation of dry ice is spontaneous only at higher temperatures

b. The sublimation of dry ice is spontaneous only at lower temperatures

c. The sublimation of dry ice is spontaneous at any temperature

d. The sublimation of dry ice is never spontaneous

The answer is A. please, explain why

Explanation / Answer

            CO2 (s) ----> CO2 (g)
Sublimation is endothermic, and the entropy for the system increases since it goes
from a solid to gas. Since H° and S° are both positive, G° is negative only when
the -TS° term dominates, and the reaction is only spontaneous at high temperatures.

Answer: A (the sublimation of dry ice is spontaneous only at higher temperatures)

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