What constitutes the degrees of freedom for a system containing liquid water in equilibrium with its vapor?
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Answer: B. 1
Explanation
Applying the Gibbs phase rule for a single-component system with two coexisting phases yields exactly one degree of freedom. The phase rule equation states that degrees of freedom equal the number of chemical components minus phases plus two. For liquid water in equilibrium with its vapor, calculating one minus two plus two gives a final result of one. The Gibbs phase rule provides a fundamental criterion for determining the thermodynamic variance of multiphase systems. A single chemical component consisting of water is represented by the chemical formula H2O in both phases. Two distinct phases exist in the system, namely the liquid phase and the vapor phase.
A zero degree of freedom system would represent a triple point where three phases coexist in invariant equilibrium. Two degrees of freedom apply to a single-phase gas or liquid system where both temperature and pressure can vary independently. Three degrees of freedom are physically impossible for any standard single-component two-phase thermodynamic system.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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