Entropy change
Entropy change
Formula
ΔS = S(products) − S(reactants) [units: J K⁻¹ mol⁻¹]
Real World
When dry ice (solid CO₂) sublimes at a concert venue, entropy increases dramatically as highly ordered solid molecules become freely moving gas particles — the same principle is used in industrial gas expansion refrigeration systems.
Exam Focus
Justify the sign of ΔS by referring to changes in number of moles of gas or change of state — vague answers about 'more disorder' rarely score full marks.
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