What two conditions need to be met for a reaction to be spontaneous?
ΛG<0 and K>1
What is the Gibbs Free Energy equation?
ΛG= ΛH- TΛS
What is entropy?
- A change in randomness
- Increases with all spontaneous reactions (2nd law of thermodynamics)
What is the first law of thermodynamics?
Energy cannot be created or destroyed
What is thermodynamics?
A prediction about whether or not a reaction will occur under the given conditions
How to calculate ΛG in standard conditions:
ΛGrxn= ΛHrxn- TΛSrxn
ΛGrxn= ΣnΛGf (products) - ΣnΛGf (reactants)
How to calculate ΛG under non-standard conditions:
ΛG= ΛG(naught)+ RTlnQ
Where R = 8.314 J/mol*K
- When at equilibrium:
- ΛG= -RTlnK
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
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
What is the faraday constant?
What is solubility?
How well something dissolves from a solid to an aqueous substance
Is E(cell) positive or negative when a reaction is spontaneous?
Ecell= E(cell)- 0.0592/n(logQ)
E(cell)= E (reduction)- E(oxidation)
What is controlled by entropy and enthalpy?
Calculating standard entropy change (spontaneity)
ΛSrxn= ΣnΛS (products) - ΣnΛS(reactants)
Calculating change in enthalpy (ΛH)
ΛHrxn= ΣnΛH (products) - ΣnΛH (reactants)
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)
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
What is Ksp
The solubility constant
How does ΛS effect entropy?
- ΛS>0, more random. Favors spontaneity
- ΛS<0, less random. Does not favor spontaneity
On the standard electrode potential chart, the most negative is the best ____ agent
On the standard electrode potential chart, the most positive is the best ____ agent
What occurs at the anode and what is its charge?
- Negative (anion)
What occurs at the cathode and what is its charge?
- Positive (cation)
What is the common oxidation number of O2?
What is the oxidation number of an element?
What is the oxidation number of a monatomic ion?