Question

In a single component system, the maximum number of phases that can co-exist in equilibrium is:

• A. 0
• B. 2
• C. 3
• D. 4

Hint:

Use Gibbs phase rule to find maximum equilibrium phases: \textbf{Triple point} is the classic case for 3-phase coexistence in a one-component system.

Answer 1

The Correct Option is C

Step 1: Apply Gibbs Phase Rule
Gibbs phase rule is given by: \[ F = C - P + 2 \] Where:
\( F \) = degrees of freedom,
\( C \) = number of components,
\( P \) = number of phases. Step 2: For a Single Component System (\( C = 1 \)) and Equilibrium (\( F = 0 \))
\[ 0 = 1 - P + 2 \quad \Rightarrow \quad P = 3 \] Step 3: Real Example
The triple point of water is a classic example of 3 phases (solid, liquid, and vapor) co-existing in equilibrium at specific temperature and pressure. Conclusion: In a single-component system, the maximum number of phases that can co-exist at equilibrium is 3.