Project ForgeThermodynamics
First Law of Thermodynamics
GATE 2008
Medium
A balloon containing an ideal gas is initially kept in an evacuated and insulated room. The balloon ruptures and the gas fills the entire room. Which statement is TRUE at the end of this process?
- AThe internal energy of the gas decreases from its initial value, but the enthalpy remains constant
- BThe internal energy of the gas increases from its initial value, but the enthalpy remains constant
- Both internal energy and enthalpy of the gas remain constant
- DBoth internal energy and enthalpy of the gas increase
Explanation
Treating balloon+room as an isolated rigid, insulated system: Q=0 and W=0, so ΔU=0 (classic free/Joule expansion). Since U depends only on T for an ideal gas, T is also unchanged, so H=U+mRT is unchanged too — both U and H remain constant.
Source: GATE ME 2008 (2008)
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