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Energy cannot be created nor destroyed, but it can be transferred between a reac

ID: 531490 • Letter: E

Question

Energy cannot be created nor destroyed, but it can be transferred between a reaction and its surroundings. The change in energy, delta E, is positive if the reaction absorbs energy, and it is negative if the reaction releases energy. You may also see this expressed in terms of changes in internal energy, delta U, For the purposes of this question, delta U and delta E are equal. One way a reaction can transfer energy to or from the surroundings is by releasing or absorbing heat A reaction Assuming constant pressure, rank these reactions from most energy released by the system to most energy absorbed by the system, based on the following descriptions: A. Surroundings get colder and the system decreases in volume B. Surroundings get hotter and the system expands in volume C surroundings get hotter and the system decreases in volume. D Surroundings get hotter and the system does not change in volume Also assume that the magnitude of the volume and temperature changes are similar among reactions. Rank from most energy released to most energy absorbed. To rank items as equivalent, overlap them.

Explanation / Answer

endothermic = gain in energy

exothermic = loss in energy

Expansive work = loss in energy

Compression work = gian in energy

a)

dE = Q + W

decrease in volume implies system gained energy; it also absorbs energy from surorundings

A > most energetic

b)

exothermic + expansive

Negative, Negative, this is the MOST releasing system

c)

exothermic + compressive, this is the 3rd most energy absorbing

d)

enxothermic, no change

so

A > C > D > B