thermo Flashcards
(52 cards)
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
