Entropy Change Calculator

Calculate System Disorder and Spontaneity

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Reaction Entropy Calculator

Calculate entropy change using standard entropies of products and reactants.

Products

Reactants

ΔS°reaction: - J/mol·K

Phase Change Entropy Calculator

Calculate entropy change for phase transitions.

ΔS: - J/mol·K

Temperature Change Entropy Calculator

Calculate entropy change for temperature changes at constant pressure.

ΔS: - J/mol·K

Understanding Entropy Change

What is Entropy?

Entropy (S) is a measure of molecular disorder and randomness in a system. Key concepts include:

  • Second Law of Thermodynamics
  • Spontaneous processes
  • System disorder
  • Heat dispersion

Entropy Changes

Common entropy changes:

  • Phase transitions
  • Temperature changes
  • Chemical reactions
  • Mixing processes
  • Gas expansion

Third Law of Thermodynamics

Key principles:

  • Perfect crystal at 0 K has zero entropy
  • All processes cease at absolute zero
  • Basis for absolute entropy values
  • Reference point for calculations

Applications

Entropy calculations are used in:

  • Chemical engineering
  • Materials science
  • Biochemical processes
  • Industrial processes
  • Environmental science

Advanced Concepts

Related concepts include:

  • Statistical entropy
  • Information theory
  • Microscopic states
  • Reversible processes
  • Heat engines

Essential Entropy Formulas

Reaction Entropy

ΔS°rxn = Σ(n × S°)products - Σ(n × S°)reactants

Phase Change Entropy

ΔS = ΔHtransition/T

Temperature Change Entropy

ΔS = Cp ln(T2/T1)