* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download text page 117 2.4 Entropy Change versus
Statistical mechanics wikipedia , lookup
Work (thermodynamics) wikipedia , lookup
State of matter wikipedia , lookup
Thermodynamic equilibrium wikipedia , lookup
Heat transfer physics wikipedia , lookup
Host–guest chemistry wikipedia , lookup
Detailed balance wikipedia , lookup
Glass transition wikipedia , lookup
Determination of equilibrium constants wikipedia , lookup
Kullback–Leibler divergence wikipedia , lookup
Chemical potential wikipedia , lookup
Rubber elasticity wikipedia , lookup
Transition state theory wikipedia , lookup
Equilibrium chemistry wikipedia , lookup
Chemical equilibrium wikipedia , lookup
Thermodynamics wikipedia , lookup
Stability constants of complexes wikipedia , lookup
Chemical thermodynamics wikipedia , lookup
2.4 Entropy Change versus Enthalpy Change • What is Entropy? • Chemical Systems and Entropy • Chemical Reactions and Entropy Change • Natural Thermodynamic Drives • Enthalpy, Entropy, and Equilibrium • Enthalpy, Entropy, and Spontaneity 2.4 Entropy Change versus Enthalpy Change What is Entropy? Chemists working definition of entropy (S) is a substance’s or system’s state of disorganization or randomness. Low Entropy Organized Simple High Entropy Disorganized Complex text page 117 2.4 Entropy Change versus Enthalpy Change Chemical Systems and Entropy Low Entropy High Entropy Atom with few electrons Molecule with few atoms Atom with many electrons Molecule with many atoms Pure Substance Substance at low temp. Solid Mixture Substance at high temp. Gas text pages 117-118 2.4 Entropy Change versus Enthalpy Change Chemical Reactions and Entropy Change A chemical equation alone does not contain enough information for you to reliably determine whether entropy increases or decreases during the reaction but: Entropy usually decreases when gas particles combine into fewer particles. text pages 119-120 2.4 Entropy Change versus Enthalpy Change Chemical Reactions and Entropy Change If the number of product gas molecules equals the number of reactant gas molecules then entropy usually decreases when the atoms of a particular element go from being: 1. 2. part of a gaseous compound to being part of a solid compound. part of different groups to being grouped together. text pages 120-121 2.4 Entropy Change versus Enthalpy Change Natural Thermodynamic Drives Two thermodynamic “drives” influence an equilibrium’s position: 1. 2. the drive toward decreasing enthalpy, i.e. in the exothermic direction. the drive toward increasing entropy or disorder. text page 122 2.4 Entropy Change versus Enthalpy Change Enthalpy, Entropy, and Equilibrium If the drive towards decreasing entropy and the drive towards increasing entropy are: 1. 2. 3. opposing then the equilibrium position will be central, with a reasonable amount of reactants and products. both towards reactants then the equilibrium position will be far to the left, i.e. almost no products. both towards products then the equilibrium position will be far to the right, i.e. the rx. goes almost to completion. text pages 122-124 2.4 Entropy Change versus Enthalpy Change Enthalpy, Entropy, and Spontaneity A spontaneous process is one that happens “on its own.” Chemical systems move spontaneously toward equilibrium. text page 125