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ISU CHE 141 - Chemical Thermodynamics 4
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CHE 141 1st Edition Lecture 30Chelate Effect and Entropy- Ni(NH3)6 2+ +3(en) reversible Ni(en)3 2+ +6NH3- This reaction occurs spontaneously (delta Grxn>0)- Displacement of NH3 by ethylenediamine is slightly exothermic and has a large delta S- 4 moles of reactants, 7 moles of products=large gain in entropy - Entropy gains drive many complexation reactions involving polydentate ligandsFree Energy Changes for Nonstandard States- Can calculate the free energy of a reaction under nonstandard conditions, delta Grxn fromdelta Grxn using: delta Grxn=delta G standard rxn + RTlnQ- Remember equilibrium constant expression and mass action expression- Q=K reactions is at equilibrium- Q<K reaction proceeds in forward direction to reach equilibrium - Q>K reaction proceeds in reverse direction to reach equilibrium - H2O reversible H2O delta G standard rxn=+8.59 o Nonspontaneous under the standard conditions thus water does not evaporate in a flask containing liquid water and water vapor under standard conditionso However water split on the floor is not under standard conditions-in open o air the partial pressure is less than 1 atm and the water evaporates spontaneouslyThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- standard conditions Qc and Qp will always be equal to 1 so delta Grxn=delta G standard rxn- under equilibrium conditions the value RT ln Q is always equal in magnitude but oppositein sign to the value in delta G standard rxn- other nonstandard conditions delta Grxn<0 thus the reaction is spontaneous in the order written, consistent with out observation of water evaporation when split on floorFree Energy and Equilibrium- delta G standard rxn determines the spontaneity of a reaction when reactants and productsare in their standard states- the equilibrium constant K tells us how far a reaction goes toward products- K is also a measure of spontaneity- If K>>1, equilibrium lies far to the right, favoring products- If K<<1 equilibrium lies far to the left, favoring reactants- K increases as delta G standard becomes more negative- When K< 1 under standard conditions: lnK<0, delta G standard rxn>0 (nonspontaneous)- When K>1 under standard conditions: ln K>0, delta G rxn<0 (spontaneous)- When K=1 under standard conditions: ln K=0, delta G standard rxn=0 (at


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ISU CHE 141 - Chemical Thermodynamics 4

Type: Lecture Note
Pages: 2
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