Question

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 the reactions.
Rank from most energy released to most energy absorbed. To rank items as equivalent, overlap them.

Answer 1

Answer:

B > D > C > A

Explanation:

For the first law of the thermodynamics, the total energy variation in a process is:

ΔU = Q - W

Where Q is the heat, and W the work. If the system loses heat, Q < 0, if it absorbs heat, Q>0. If work is done in the system (volume decreases), W < 0, if the system does the work (volume increases), W > 0.

A. If the surroundings get colder, the system is absorbing heat, so Q>0, and the system decreases in volume so W < 0 :

ΔU = +Q - (-W) = +Q + W (absorbs a higher energy)

B. If the surroundings ger hotter, the system is losing heat, so Q<0, and the system expands, so W>0:

ΔU = -Q -W (loses higher energy)

C. Surroundings get hotter, Q<0, and the system decreases in volume, W<0

ΔU = - Q + W = 0 (magnitude of heat and work is similar)

D. Surroundings get hotter, Q<0, and the system is not changing in volume, W = 0.

ΔU = -Q (loses energy)

For the most released (more negative) for the most absorbed (most positive):

B > D > C > A