Chem test 4

  1. What two conditions need to be met for a reaction to be spontaneous?
    ΛG<0 and K>1
  2. What is the Gibbs Free Energy equation?
    ΛG= ΛH- TΛS
  3. What is entropy?
    • A change in randomness
    • Increases with all spontaneous reactions (2nd law of thermodynamics)
  4. What is the first law of thermodynamics?
    Energy cannot be created or destroyed
  5. What is thermodynamics?
    A prediction about whether or not a reaction will occur under the given conditions
  6. How to calculate ΛG in standard conditions:
    ΛGrxn= ΛHrxn- TΛSrxn


    ΛGrxn= ΣnΛGf (products) - ΣnΛGf (reactants)
  7. How to calculate ΛG under non-standard conditions:
    ΛG= ΛG(naught)+ RTlnQ

    Where R = 8.314 J/mol*K

    • When at equilibrium: 
    • ΛG= -RTlnK
  8. What are the factors that affect entropy?
    • State: gas>liquid>solid
    • Molecular mass and complexity: more = more entropy
    • Allotropy: More irregular = higher
    • Dissolution: Solution>pure solvent/ solute alone
  9. What are the standard states?
    • Gas: pure gas at 1 atm 
    • Solid Liquid: Pure solid/liquid in it's most stable form
    • Temperature: 25C
    • Solution: Solute concentration 1M
  10. What is the faraday constant?
    96,485 F
  11. What is solubility?
    How well something dissolves from a solid to an aqueous substance
  12. Is E(cell) positive or negative when a reaction is spontaneous?
  13. Nernst Equation
    Ecell= E(cell)- 0.0592/n(logQ)
  14. Calculating E(cell)
    E(cell)= E (reduction)- E(oxidation)

  15. What is controlled by entropy and enthalpy?
    Spontineity (ΛS)
  16. Calculating standard entropy change (spontaneity)
    ΛSrxn= ΣnΛS (products) - ΣnΛS(reactants)
  17. Calculating change in enthalpy (ΛH)
    ΛHrxn= ΣnΛH (products) - ΣnΛH (reactants)
  18. Factors that affect solubility
    • Common ion effect- Adding ions shifts equation to the left, because [] of ions has increased
    • pH effect- Metal hydroxides are more soluble when the pH is low (basic)
    • Compounds containing anions that are the conjugate bases of weak acids are more soluble with a low pH (basic)
  19. How is precipitation predicted with Q values?
    • Q>1, precipitation forms. Reaction shifts left 
    • Q<1, no precipitation forms. Reaction shifts right
    • Q=1, precipitation on the cusp of forming. Reaction does not shift
  20. What is Ksp
    The solubility constant
  21. How does ΛS effect entropy?
    • ΛS>0, more random. Favors spontaneity 
    • ΛS<0, less random. Does not favor spontaneity
  22. On the standard electrode potential chart, the most negative is the best ____ agent
  23. On the standard electrode potential chart, the most positive is the best ____ agent
  24. What occurs at the anode and what is its charge?
    • Oxidation 
    • Negative (anion)
  25. What occurs at the cathode and what is its charge?
    • Reduction 
    • Positive (cation)
  26. What is the common oxidation number of O2?
  27. What is the oxidation number of an element?
  28. What is the oxidation number of a monatomic ion?
    It's charge
Card Set
Chem test 4
Equations and concepts for chem 111 test 4