Answer:
C. change in internal energy is zero
Explanation:
Let's say we have a scenario of an ideal gas which is in a system that is isolated, and which is filled inside a flask that is connected to another flask and separated by a valve. If this valve gets to be opened, the gas is going to spontaneously fill the other flask through expansion.
Then we would have
work done , W = -P∆V = 0.
With vacuum, P equal 0.
Since there is a complete isolation of this system, we would have bit that no heat exchange is happening.
Q = 0
Using the first law of thermodynamics,
∆U= Q + W = 0
Therefore we conclude that the change in internal energy is zero
