University College - Chemistry Chem 112A Study Guide - Quiz Guide: Reaction Coordinate, Reaction Quotient
14 Aug 2018
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Department
Professor
Quiz 6:
Formulas:
∆G˚ = ∆H˚ – T∆S˚
- Standard state free energy using standard state enthalpy and entropy
∆Grxn = ∑nG(products) – ∑nG(reactants)
∆G˚ = – RTlnK
- Related K (Ka/sp/b etc) to ∆G
∆G = ∆G˚ + RTln(Q/K)
- Standard state + temperature and reaction quotient (Products/Reactants)
ln(K2/K1) = –∆H˚/R(1/T2 – 1/T1)
- 2 temperatures given; can be used to find ∆H˚
- Can break apart and do lnK(@T2) – lnK(@T1)
Concepts:
- Dependence of free energy on pressure:
o ∆S = nRln(V2/V1)
o ∆S = Rln(P1/P2)
o Therefore → ∆G = ∆H – T(Rln(P1/P2)
- Non-standard state free energy
o ∆Grxn = ∑nG(products) – ∑nG(reactants)
o Can also use activities of the products and the reactants for reaction
quotient
▪ Can be found with product/reactant
▪ May also use an ICE table to find K if it is standard ∆G
- ∆G, K and Q relationships
Spontaneous
Q vs K
∆G
Forward
Q < K
∆G < 0
Reverse
Q > K
∆G > 0
Equilibrium
Q = K
∆G = 0
- Temperature dependence of K
o If ∆H˚ > 0 → K increases with increase in temperature (endothermic)
o If ∆H˚ < 0 → K decreases with increase in temperature (exothermic)
- Graph (Total free energy v. reaction coordinate)
Document Summary
Standard state free energy using standard state enthalpy and entropy. Standard state + temperature and reaction quotient (products/reactants) G = g + rtln(cid:523)q/k(cid:524) ln(k2/k1) = ( /r(cid:523)(cid:883)/t2 1/t1) (cid:884) temperatures given; can be used to find ( . Can break apart and do lnk(@t2) lnk(@t1: s = nrln(v2/v1, s = rln(p1/p2, therefore g = ( t(rln(p1/p2, grxn = ng(cid:523)products(cid:524) ng(cid:523)reactants(cid:524) Concepts: can also use activities of the products and the reactants for reaction quotient, can be found with product/reactant, may also use an )ce table to find k if it is standard g. Temperature dependence of k: )f ( > (cid:882) k increases with increase in temperature (endothermic, )f ( < (cid:882) k decreases with increase in temperature (exothermic) Graph (total free energy v. reaction coordinate)
