Cup a and cup b are identical. they contain equal volumes of soup at equal temperatures. both cups are put in a refrigerator. cup a has a lid, but cup b does not. which statement best explains why cup a will cool more slowly than cup b?

a.
water vapor won’t be able to escape from cup a.
b.
the most energetic water molecules from cup a will escape more rapidly.
c.
no molecules will be able to evaporate at the surface of cup b.
d.
no molecules will be able to evaporate at the surface of cup a.

Option (D) is the correct answer.

Explanation:

It is known that in a closed system there will no exchange of heat or matter from the system to the surrounding. Whereas in an open system there will be exchange of both heat and energy from the system to the surrounding and vice versa.

Therefore, in the given situation cup A is a closed system and cup B is an open system. Hence, there will be no exchange of heat or matter from cup A to system and surrounding. So, it will cool slowly that cup B.

Thus, we can conclude that the statement no molecules will be able to evaporate at the surface of cup A, best explains why cup A will cool more slowly than cup B.

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.