Unit 10 - Redox - Honors Flashcards
What conditions determines if a reaction will be spontaneous?
- ΔG (Constant Temp. & Pressure)
- ΔH (Exothermic)
- ΔS (More Entropy)
What can Gibbs Free Energy (ΔG) be used to determine? (3)
- Determine the effect of T, P and [ ] on rxn spontaneity
- Calculate Keq
- Determine if coupled rxns will be spontaneous
Definition of Gibbs Free Energy (ΔG) (10)
- Measure of the driving force of a rxn
- Rxns go in a certain direction to decrease the free E of a system
- ΔG represent the portion of the total energy change that is free to do work
- ex: If ΔG for rxn is -270J, it is possible to obtain 270 kJ of useful work from that rxn
- ex: If ΔG for rxn is +270 kJ, at least 270 kJ of E must be supplied to make the rxn to take place
- ΔG < 0 = Spontaneous Rxn
- ΔG > 0 = Non Spontaneous Rxn, Reverse Rxn will Occur
- If ΔG = 0, system is at equilibrium, rxn will occur in either direction
- G products < G reactants, fwd rxn will occur
- G products > G reactants, no driving force to make the rxn go in either direction
What is the Gibbs - Helmholtz Equation? (3)
- ΔG = ΔH - T ΔS
- H = enthalpy, T = temp in K, S = entropy
- ΔH & + ΔS tend to make ΔG negative
IMPORTANT FOR AP CHEM
Thermodynamics, Equilibrium & Electrochemistry
A reaction will be spontaneous when:
ΔG = Negative
E° = Positive
Keq > 1
If a person has thermodynamic data, they should be able to relate that to equilibrium
Definition of Watt
Work/Power per Unit Time (joules/sec)
Definition of Amp
Unit of Current (flow rate)
Number of coulombs/sec
Definition of Voltage
Electrical Pressure
Definition of Ohms
Unit for Resistance
Definition of Resistance
Diameter, length, temperature and material (resistivity)
Definition of E° Cell Potential
- E Cell is the Standard Cell Potential
- E Cathode is the Standard Reduction Potential
- For the Reduction Half Rxn Occuring at the Cathode
- E Anode is the Standard Reduction Potential
- For the Oxidation Half Rxn Occurring at the Anode
Definition of Coulomb (3)
- SI unit of electric charge
- Quantity of electric charge
- Transported by a current of 1 ampere flowing for 1 sec
What is the formula to determine the E Cell (7)
- E Cell = E (Cathode) + E (Anode)
- Split Equation into Half Rxns
- Use Standard Reduction Potential Table
- To find the Reduction & Oxidation Potentials
- For Oxidation Potentials, Change the Sign for the Voltage
- Add both values together
- If positive, rxn is spontaneous
What happens if you double the equation? (2)
- Does NOT double the potential
- Will affect current, but not voltage
