# Entropy - Gibbs Free energy

 Entropy is an important concept in chemistry because it is the basis for predicting the natural ______ of a reaction. Keep in mind, both the entropy of _______ & _______ change as heat produced enters or leaves them. directionsystem and surroundings If reaction is ________, heat is released into the surrounding and their entropy increases (ΔSsurr > 0). If the reaction is _______, heat leaves the surroundings, so their entropy decreases (ΔSsurr < 0). exothermicendothermic To calculate the change in entropy that accompanies a reaction, we need to know the _____ entropies of all the substances taking part; then we calculate the difference between the entropies of the _____ and those of the ______. What is this called? molar productsreactantsstandard reaction entropy (ΔS°) Standard reaction entropy is the difference between the stand molar entropies of the ______ and those of the _______ while taking into account the ________ _______. State the formula products reactantsstoichiometric coefficientsΔS°=ΣnSm°(products) - ΣnSm°(reactants) Explain ΣnSm°(products), also state expected units It is a sum of standard molar entropies of products multiplied (respectively) by their stoichiometric coefficientsJ*K-1mol-1 A process is spontaneous only if the TOTAL change in _____, the sum of the changes in the _____ and _______ is positive. So, we must 1st calculate change in entropy of _______ and then add that change to the change of the ______. This goes in accordance with the second law when we realize it refers to ______ systems entropysystem & surroundingsurroundingsystemisolated Equation for calculating total entropy change with regards to spontaneity ΔStot= ΔS + ΔSsurr meaning, entropy change of system plus entropy change of surrounding It is critical to understand that a process in which ΔS decreases may be spontaneous, provided that the entropy of the surroundings _______ so much that the ΔStot increases. State an example increasesfreezing of water In reactions where ΔS decreases but ΔSsurr makes ΔStot positive, like in water, when we try to calculate entropy change of surroundings, we must recognize which 4 steps and state the final equation: *also what is T in? Surroundings are taken to be large,so their temp remains constant, no matter how much energy is transferred (ΔSsurr=qsurr,rev/T)The heat that leaves the system enters the surroundings, qsurr=-qFor a system maintained at constant pressure the heat that leaves the system can be equated to the change in enthalpy of the system and we can write q = ΔH & ∴ qsurr=-ΔHDue large surroundings, any transfer of heat into them will, from their perspective, be so small that it can be regarded as occuring reversibly and hence qsurr,rev=-ΔH equation: ΔSsurr=-(ΔH/T) or (qsurr,rev/T), T is in Kelvin The equation ΔSsurr=-(ΔH/T) can be derived when any change takes place in a system maintained at ______ pressure and ______ temperature constant constant ΔHfus=ΔHfreeze True or False False: ΔHfus=-ΔHfreeze If ΔStot is positive (an increase), the process is ______. If ΔStot is negative (a decrease), the reverse process is ________.  If ΔStot = 0, the process has no tendency to proceed in ______ direction spontaneous spontaneouseither A process produces maximum work if it takes place _______. So wrev is more negative than wirrev, meaning, more energy leaves the system as ______ in wrev. As a result, we can state that qrev should also be _____  than qirrev. reversiblyworkgreater The clausius inequality exists because if you replace qrev with qirrev, ΔS >qirrev. State the Clausius inequality and explain the equality. ΔS ≥ q/TThe equality would only be valid for reversible processes. For fully isolated systems, q =__ for any process taking place inside the system. Therefore, ΔS ≥ ___ for any process inside an isolated system. Entropy cannot ______ in isolated systems which is a direct result of the _____ law of thermodynamics. So the entropy of the universe must be steadily ______ 00decreasesecondincreasing Reversible and irreversible paths between two given states of the system leave the surroundings in _____ states. This is because entropy is a state function, the value of ΔS, is ______ for both paths but ΔStot is _______ in both paths because entropy of surroundings is _____ for both paths different similar different different Memorize the table Equation for qsurr under reversible isothermal conditions qsurr=-nRTln(V2/V1) How much work is done in free expansion? zero ΔS is the same in both ______ & ______ pathways reversible and irreversible Does a system at equilibrium go in the reverse or forward direction? neither Outside of summing up entropy of the system and of the surrounding, name another concept that can help determine spontaneity of a reaction Gibbs free energy Gibbs free energy is defined solely in terms of ______ _______, and so G is a _____ ______. State the formula for both Gibbs free energy and change in Gibbs free energy and also state their given scenarios G = H - TS (constant temp and constant pressure)ΔG = ΔH - TΔS (constant temp) Formula for Gibbs free energy at constant temperature AND pressure. The minus sign in this equation means that as long as temp and press. are constant, a(n) ______ in total entropy corresponds to a(n )______ in Gibbs free energy. As a result, under these conditions, the direction of spontaneous change is the direction of ______ Gibbs free energy. ΔG = -TΔStotincreasedecreasedecreasing  Use the following table to predict spontaneity and value of Gibbs free energy At constant temperature and pressure, we know that if ΔG = 0, the system is in _______ equilibrium State 1 (expected) example of atoms, 3 examples of linear molecules and 3 examples of nonlinear molecules atoms: argon or other ideal gases (monatomic)linear molecules: any diatomic molecules, carbon dioxide, ethyne or acetylenenonlinear molecules: water, methane or benzene List the Cv,ms and Cp,ms for atoms, linear molecules and non-linear molecules What is the Cvm of O2 under ideal conditions vs not under ideal conditions? Under ideal conditions, it behaves naturally like a linear molecule at 5/2RUnder non-ideal conditions it behaves like an atom at 3/2R Authorchikeokjr ID327992 Card SetEntropy - Gibbs Free energy DescriptionExamples 9.9-9.15 Updated2017-03-09T04:41:21Z Show Answers