thermo Flashcards
What is a spontaneous process
a process that occurs without outside intervention
What is true about chemical systems
they want to be at the lowest chemical energy
What is Gibbs free energy
it is a thermodynamic state function where chemical systems tend towards the lowest chemical potential also called Gibbs Free Energy
Why is Gibbs free energy called the chemical potential
it determines the direction of chemical systems
what corresponds to a spontaneous process
a decrease (negative) in ∆G
what corresponds to a nonspontaneous process
an increase (positive) ∆G
When is ∆G at equilibrium?
When it equals zero, that is the lowest chemical potential
How is ∆G calculated?
Gfinal-Ginitial
or ∆H-T∆S
When is the change in enthalpy exothermic?
When ∆H is negative (energy/heat is released)
When is the change in enthalpy endothermic?
When ∆H is positive (energy/heat is absorbed)
What is Entropy (∆S)
It is the number of energetically equivalent ways to arrange a component of a system
when there are more ways to arrange the particles, the particles are more randomized in the chemical system (increase in Entropy)
When ∆S is positive
The entropy has increased
What are the four changes that increase entropy
Phase change
Increases in temperature
Reactions where there are a larger # of product molecules than reactant molecules
Solids dissociating in water
How does ∆G relate to temperature?
It is temperature dependent based on the context
In the equation ∆G=∆H-T∆S, what are the two cases when ∆G is temperature dependent?
When ∆H = (+) and ∆S=(+)
When ∆H=(-) and ∆S=(-)
When is ∆G nonspontaneous at all temperatures?
When ∆H = (+) and ∆S= (-)
When is ∆G spontaneous at all temperatures
When ∆H=(-), ∆S=(+)
When are the standard conditions?
For solutions, the concentrations are @ 1M
For gas, the pressure is = 1 atm
For temp, 25C and 298K is the most stable temperature
When is the ∆Gf of an element = to zero?
When it is in its elemental state
What affects the standard molar entropy?
A particle in its gaseous state has a higher entropy since it has more ways to arrange its particles
When an atom increases its size (down a column) it has more space for energy to disperse
More complex molecules (more atoms) have more ways to arrange those atoms and have more ways to disperse eneergy
Dissolution of a solid to liquid allows for more ways to arrange particles
When we lose moles in a reaction, what happens to the entropy?
The entropy decreases
How to find Gibbs Free Energy under non-standard conditions
∆G=∆G°+RTlnQ
What does it mean when ∆G° is negative
It is spontaneous in the forward direction, it is product favored K>1
What does it mean when ∆G° is positive
It is nonspontaneous in the forward direction, it is reactant-favored K<1
When ∆G is negative what does it mean in relation to spontaneity and K
it is spontaneous in the forward direction and is product favored
K>1
When ∆G is positive, what does it mean in relation to spontaneity and K
it is nonspontaneous in the forward direction and is reactant favored
K<1
What is an oxidation-reduction reaction
the transfer of electrons from one substance to another
what is oxidation
the loss of electrons
what is reduction
the gain of electrons
What does it mean to be the reducing agent
it is the substance that is oxidized and it loses the electrons so that the other substance gains them
what does it mean to be the oxidizing agent
it is the substance that is reduced, it gains the electrons that the oxidized element loses
what is the electrical current
it is the flow of electrons driven by the difference in potential energy
what is a voltaic cell
it is a electrochemical cell that produces an electrical current from a spontaneous redox reaction
What happens at the anode?
it is the site of oxidation, it is where electrons are produced to flow to the cathode
it has a higher potential energy since it has more electrons
what happens at the cathode
it is the site of reduction, it has a lower potential energy so electrons flow here
How do electrons move from anode to cathode
they move spontaneously by the change in potential energy between the anode and the cathode
When E°Cell is positive
the reaction is spontaneous
When E°cell is negative
the reaction is nonspontaneous
What is E° Cell
The chemical potential at standard conditions
what is E cell
the chemical potential at non-standard conditions
what is SHE
it is the standard hydrogen electrode that has a potential of 0.00 V
On the Reduction Half-Reaction table, what is the left hand side?
the oxidizing agents (they are reduced (consume electrons))
What is the right hand side of the Reduction Half-Reaction table?
they are reducing agents (they are oxidized)
What does it mean that F has the highest placement on the Reduction Half Reaction table?
it is the best- oxidizing agent
what does it mean to be higher up (more positive) on the reduction half-reaction table?
it favors reduction
what does it mean to be lower (more negative) on the reduction half-reaction table?
it favors oxidation (the back reaction)
Reactions on the higher end of the table tend to be better ______ agents
while reactions on the lower end of the table tend to be better _______ agents
oxidizing agents
reducing agents
All half reactions are written as
reductions
When E° is more positive on the table
it is reduction favored
(PIR)
positive is reduction
When E° is more negative on the table
oxidation is favored
(NIO)
negative is oxidation
In general what is true about oxidizing agents and reducing agents on the table and their placements above or below other reactions?
an oxidizing agent will oxidize any reducing agent below it
a reducing agent will reduce an oxidizing agent above it
