Gibbs Phase Rule Calculator
Calculate degrees of freedom for thermodynamic systems using Gibbs' phase rule F = C - P + 2
Calculate Degrees of Freedom
Minimum number of chemical species needed to define all phases
Number of distinct homogeneous regions in the system
Phase Rule Results
Gibbs' Phase Rule: F = C - P + 2
Calculation: 1 - 1 + 2 = 2
System Analysis: Two variables can be changed independently (e.g., temperature AND pressure).
Phase Description: Single phase present (solid, liquid, or gas)
Example Chemical Systems
Pure Water System
Water at triple point (ice, liquid, vapor)
H₂O in three phases
Water-Salt Solution
Saltwater with solid salt precipitate
NaCl + H₂O system
Calcium Carbonate Decomposition
CaCO₃(s) ⇌ CaO(s) + CO₂(g)
Three components, three phases
Binary Alloy System
Homogeneous metal alloy
Two metals in single solid phase
Ammonia Synthesis
N₂ + 3H₂ ⇌ 2NH₃ (gas phase)
Single component in equilibrium
Degrees of Freedom Guide
F = 0 (Invariant)
No variables can change
Example: Triple point of water
F = 1 (Univariant)
One variable can change
Example: Boiling water (T or P)
F = 2 (Bivariant)
Two variables can change
Example: Pure gas (T and P)
F ≥ 3 (Multivariant)
Multiple variables can change
Example: Multi-component solutions
Phase Types
Component Examples
Understanding Gibbs' Phase Rule
What is Gibbs' Phase Rule?
Gibbs' phase rule, proposed by Josiah Willard Gibbs in 1875, is a fundamental principle in thermodynamics that relates the number of degrees of freedom in a system to the number of components and phases present. It provides a framework for understanding phase equilibria and predicting system behavior.
Key Definitions
- •Component (C): Minimum number of chemical species needed to define all phases
- •Phase (P): Distinct homogeneous regions with uniform properties
- •Degrees of Freedom (F): Number of variables that can be changed independently
The Phase Rule Equation
General Formula
F = C - P + n
F = Degrees of freedom
C = Number of components
P = Number of phases
n = Number of intensive variables (usually 2: T and P)
Standard Form
F = C - P + 2
Most common form assuming temperature and pressure as variables
Modified Forms
F = C - P + 1 (T or P constant)
F = C - P + 0 (T and P constant)
Practical Applications
Phase Diagrams
Understanding regions where different phases exist and coexist in equilibrium.
Materials Science
Designing alloys and understanding phase transformations in materials.
Chemical Processing
Optimizing separation processes and reaction conditions in industry.