First Law of Thermodynamics Practice Problems

Which of the following represent q and w for a system that is doing work on the surroundings and losing heat to surroundings?

a) q > 0, w > 0

b) q > 0, w < 0

c) q = 0, w > 0

d) q < 0, w = 0

e) q < 0, w < 0

f) q < 0, w > 0

Which of the following is the best interpretation of the First Law of Thermodynamics?

a) The total work of the universe is decreasing.

b) The total mass of the universe is increasing.

c) The total energy of the universe is constant.

d) The total heat of the universe is decreasing.

e) The total enthalpy of the universe is increasing.

f) The total entropy of the universe is constant.

Which of the following reactions do work on the surroundings at constant pressure?

I. X(s) + 3 Y(g) → 2 Zg)

II. 2 X(g) + Y(g) → 4 Z(g)

III. X(s) + 2 Y(g) → 3 Z(g)

IV. 2 X(g) + 2 Y(g) → 3 Z(g)