In a steam engine,steam in a cylinder expands against a piston exerting 10.00 atm of external pressure.The volume of the cylinder increases by 10.00 L and simultaneously the steam cools,losing 3.000 $\times$10³ kJ of energy to the surroundings.What is the change in energy of the steam? (101.3 J = 1 L.atm)

Question

Quizplus · Accepted Answer

We can use the first law of thermodynamics to solve this problem:
ΔE = Q - W
where ΔE is the change in energy of the system, Q is the heat transferred to or from the system, and W is the work done by or on the system.
Since the volume of the cylinder increases and the external pressure is constant, the work done by the system is:
W = -PextΔV = -(10.00 atm) * (10.00 L) = -100.0 L*atm = -100.0 J
Note that we had to convert the units of L*atm to J using the conversion factor given in the problem.
The heat transferred to the surroundings is given as Q = -3.000 kJ.
Therefore, the change in energy of the steam is:
ΔE = Q - W = (-3.000 kJ) - (-100.0 J) = -3.010 kJ
Since we were asked for the answer in kJ, we can choose option (A) as the correct answer.

In a Steam Engine,steam in a Cylinder Expands Against a Piston