When 2 litre of ideal gas expands isothermally into vacuum to a total volume of 6 litre, the change in internal energy is J. (Nearest integer)
Your answer stays private
What feels right?
Hint 1 of 2
What thermodynamic state variable determines the internal energy of an ideal gas?
No score. Commit to your first instinct. We’ll show what your mind noticed and what it missed.
Type the value - units or words beside it are fine.
Step-by-step solutionView
Correct answer
The change in internal energy is 0 J because the internal energy of an ideal gas depends solely on temperature, which remains constant during an isothermal process.
Option analysis
Why each option works or fails
Reviewed route
Solution
StepWorking
✓quick_kill
For an ideal gas, internal energy depends solely on temperature: U=f(T), so ΔU=nCvΔT. Since the expansion is isothermal, ΔT=0, which immediately gives ΔU=0 J.
Hints that build this answer step by step
What thermodynamic state variable determines the internal energy of an ideal gas?
Temperature only (U=f(T))
Given that the expansion is isothermal, what is the temperature change ΔT and the resulting change in internal energy ΔU?
Does expanding into a vacuum (free expansion) affect whether internal energy changes?
No. For an ideal gas, ΔU depends only on temperature regardless of whether the expansion is against an external pressure or into a vacuum. Because the process is isothermal, ΔT=0, so ΔU=0.