NEET Physics Heat Engines MCQ Question
Consider a sealed container containing a fixed amount of liquid water at its boiling point. The container is heated at constant pressure until all the liquid has evaporated into steam. Which of the following best describes the enthalpy change for this process?
It is equal to the standard enthalpy of vaporization, 999vapH999.
It is negative because heat is released when water evaporates.
It is zero because the system is at equilibrium at boiling point.
It is variable depending on the volume change of the system.
Correct Answer
Detailed Explanation
The enthalpy change for the vaporization of water at its boiling point and constant pressure is equal to the standard enthalpy of vaporization, 999vapH999, which is positive because heat is absorbed.
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