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internal energy (u)
the sum of the kinetic and potential energies of the particles making up the system
U = Pe + Ke
State function
A property of a system that depends onyl on its present state, independent of the path in which the system took to get to this state
U is a
state function
Work (W)
the energy exchanged that results when a force (F) moves an object through a distance (d)
W = F.d
work positive
work done on the system by the surroundings
work negative
work done by the system on the surroundings
heat (q)
the energy that flows into or out of a system
q positive
endothermic, heat gained by the system
q negative
exothermic, heat lost by the system
1st law thermodynamics
the change in internal energy of a system, u, equals to q + w
U = q + w
enthalpy
H = U + PV
enthalpy is a
state function
the change in enthalpy
is the heat of the reaction when its conducted at constant pressure
spontaneous process
a physical or chemical change that occurs by itself
entropy (S)
a thermodynamic quantity that measures the randomness or disorder in a system
entropy positive
system moves to more disorder
entropy negative
system moves to more order
2nd law of thermodynamics
the total entropy of a system and its surroundings always increases for a spontaneous process
no process is 100% efficient
boltzmann equation
S = k lnW
3rd law of thermodynamics
the entropy of a perfect solid at 0K is 0
entropy change for a phase transition
S = Hfus/T
entropy increases when
a molecule is broken into two or more smaller molecules
there’s an increase in moles of gas
a solid changes to a liquid or gas, or a liquid to a solid
free energy
energy available to do work
G = H - TS
G large negative number
spontaneous, reactants go almost entirely to product
G large positive number
nonspontaneous, reactants dont give a significant amount of product
G at 0
reaction at equilibrium
G small negative or positive number
reaction is close to equilibrium
maximum work
the free energy
enthalpy positive, entropy positive, free energy negative
spontaneous at any T
enthalpy positive, entropy negative, free energy positive
nonspontaneous at any T
enthalpy negative, entropy negative, free energy negative or positive
spontaneous at low T
nonspontaneous at high T
enthalpy positive, entropy positive, free energy negative or positive
spontaneous at high T
nonspontaneous at low T
transition temperature
T = enthalpy/entropy (under standard conditions)
at equilibrium the free energy is
0 and the equilibrium constant is equal to the reaction quotient
free energy and equilibrium constant
G = -RT lnk
free energy and voltage
G = -nFE
E is energy (volts produced)
Note
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