Chemistry Chapter 19 Notes!
Chemistry Chapter 19 Notes! CHEM 130 - 003
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This 0 page Class Notes was uploaded by Izabella Nill Gomez on Friday November 13, 2015. The Class Notes belongs to CHEM 130 - 003 at University of Tennessee - Knoxville taught by Bin Zhao in Summer 2015. Since its upload, it has received 25 views. For similar materials see General Chemistry II in Chemistry at University of Tennessee - Knoxville.
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Date Created: 11/13/15
Chemistry 130 Chapter 19 Notes Spontaneous process one that proceeds on its own without any outside assistance Occurs in one direction only and reverse process is nonspontaneous Ex gas spontaneously expands into a vacuum but the reverse process does not happen In general processes spontaneous in one direction are nonspontaneous in the other Depending on a temperature a process can be spontaneous or not Ex spontaneous ice melting at Tgt0 deg C Thermodynamics tells of the direction and extent of a reaction but not the speed Reversible process speci c way in which a system changes state by exactly reversing the state the system and surroundings can be restored to the original state no net change Irreversible process one in which the system and surroundings cannot simply be reversed to restore to original state Ex heat flow to colder objects Reversible change produces the maximum amount of work that can be done by a system on its surroundings Isothermal process expansion of ideal gas at a constant temperature Gas expands spontaneously with no external pressure no PV work on surroundings w0 Any spontaneous process is irreversible Entropy associated with the extent of randomnessdisorder in a system or the extent to which energy is distributed among the various motions of the molecules of A S S nal S initial the system is a state function qrev For an isothermal process where delta S is for any isothermal process qrev is heat for the reversible process but applies to other processes as well and T is the absolute temperature Melting of a substance at the melting point and vaporization of a substance at the qrev A Hfusion fusion T T boiling point are isothermal processes qZAHfusionAS For a spontaneous process the total change in entropy sum of entropy change of the system plus the surroundings is greater than zero Generay when a solid is dissolved in a solvent entropy increases The dissolving of a salt in water involves both a disordering process the ions become less con ned and an ordering process some water molecules become more con ned The disordering processes are usually dominant Second law of thermodynamics any reversible process results in an increase in total entropy whereas any reversible process results in no overall change in entropy A S universe A S system A S Surroundings 0 Reversible AS AS AS universe system surroundings gt IrreverSIble 0 The entropy of the universe increases in any spontaneous process Microstate Single possible arrangement of the positions and kinetic energies of the gas molecules when the gas is in a speci c thermodynamic state It consists of a particular microscopic arrangement of atoms or molecules of the system that corresponds to its state Number of microstates in a system is W Sk In W Entropy is a measure of how many microstates are associated with a W ASk1n Jim initial particular microscopic state Entropy increases with the number of microstates in a system Entropy increases in a gas as volume increases Also increases with increasing temperature Molecules exhibit transationa motion movement of a molecule from one place to another vibrational motion periodic motion of atoms within a molecule rotational motion rotation of a molecule about an axis the number of microstates for a system increases with an increase in volume temperature or an increase in the number of molecules because any of these changes increases the possible positions and kinetic energies of the molecules making up the system The number of microstates also increases with the complexity of molecules more vibrational motions are available Entropy increases for 1 Gas formation from solids or liquids 2 Liquids or solutions formation from solids 3 The number of gas molecules that increase during a chemical reaction lf thermal energy is decreased by lower temperatures the energy of motion decreases and entropy decreases The third law of Thermodynamics entropy of a pure crystalline substance at an absolute zero is zero SO K0 The order is perfect among molecules no thermal motion only one microstate WS k In 10 0 Standard molar entropies S 1 At 298 K it is not zero 2 For gases it is greater than when liquid or solid 3 Generally increases with increasing molar mass 4 Generally increases with an increasing number of atoms in the formula of a substance ASOZEnSOpr0ducts mSOreactants 8 is for sum qsystem A H system For isothermal processes ASsurrrmnah39ngs T V T Spontaneous processes that result in a decrease of entropy are always exothermic Gibbs free energy GzH TAS AH tem AS AS AS AS sys universe system surroundings system T If AGlt0 reaction is spontaneous in the forward direction If AGZO reaction is at equilibrium lf AGgtO reaction in the forward direction is nonspontaneous but spontaneous in the reverse reaction AG It is more convenient to use as a criterion for spontaneity instead of AS AG universe because refers to the system alone In any spontaneous process carried out at constant temperature and pressure free energy always decreases 0 Standard free energies of formation AGf A GE 2 811 G0 products 8m G0 reactants 9 eacUon 5 pontaneous at all T 6 Nonspontaneous at all T Spontaneous at low T nonspontaneous 2 2 2 z z at high T Spontaneous at high T or nonspontaneous at low T