The Gibbs phase rule
For equilibrium among phases in a system described by independent components, the Gibbs phase rule gives F=C−P+2.
Key knowledge
For equilibrium among phases in a system described by independent components, the Gibbs phase rule gives F=C−P+2. F counts independent intensive variables such as temperature, pressure and phase compositions; fixing an independent variable reduces the available freedom.
Values and equations
F = C − P + 2
- F
- number of independent intensive degrees of freedom 1
- C
- independent component count 1
- P
- coexisting phase count 1
Conditions and scope
- Use the independent component count after reaction constraints; assume equilibrium and the usual temperature–pressure/composition description.
- Additional field variables or imposed constraints require appropriate adjustment; the rule does not calculate phase boundaries.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Inspected IUPAC's F=C−P+2 definition; scope specifies components and intensive freedom.
2026-10-10 · Independent AI editorial review: All 94 actual compact claims, hypotheses, equation/variable/unit tables and 176 origin semantic links independently read. All exact author source-binding rows and disclosed extents assessed; targeted original bodies or specifically identified indexed primary passages rechecked below. All retained chemistry compact records read for combined breadth. Independent AI editorial content and practical common-core inventory review; no human specialist, degree/laboratory proficiency, whole-textbook certification or experimental replication. Receipt: chemistry-independent-content-inventory-review.1.
Entry details
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