Thermodynamics Flashcards
What is THERMODYNAMICS
Study of energy changes in relation with physical or chemical processes
2 main terms in THERMODYNAMICS
System & Surroundings
A system can either be….
a chemical reaction or physical process
Intensive vs Extensive Property
I: does not depend on amount of substance
E: depends on amount of substance
What is Energy?
Capacity to do work or transfer heat
1 cal is = to?
4.184 J
3 types of Systems
Open - exchange of heat and matter thru system
Closed - exchange of only heat thru system
Isolated - does not allow exchange of anything
What is Internal Energy
- sum of energies of all the particles in a system
Formula for Internal Energy (3)
E or U = PE + KE
ΔE = E final- E initial
ΔE = q + w
Potential Energy VS Kinetic Energy
PE: from interactions between particles
KE: types of motion
3 types of KE
- Rotational
- Translational
- Vibrational
Endothermic vs Exothermic
Endo = + value / gaining of heat
Exo = - value / releasing of heat
What do the positive and negative values of q and w meaning?
q + = system gained heat
q - = system lost heat
w + = work done ON the system
w - = work done BY the system
What is PV work?
Formula
Work done by an EXPANDING gas
w = -PΔV
How many Joules is 1 L-atm?
101.3 J
1st Law of Thermodynamics (2)
Law of Conservation of energy
“The total energy in the universe is constant”
+ Change in ENTHALPY
ΔE universe is = to?
ΔE system + ΔE surroundings = 0
What is ENTHALPY?
unit?
formulas (2)?
Total heat content of a system
ΔH
ΔH = ΔE system + PV
ΔH = H products - H reactants
Is HEAT an extensive or intensive property
extensive
Where is heat in the equation of:
- Endothermic Rxns
- Exothermic Rxns
ENDO = reactants
EXO = products
Identify if EXO or ENDO:
S -> L -> G
G -> L -> S
+ which has highest and lowest energy state?
- ENDO
- EXO
GAS = highest energy state kasi requires the highest amount of heat to retain that phase
MANIPULATING THERMOCHEMICAL EQUATIONS
If:
1. Equation is reversed, what happens to ΔH?
2. Equation is multiplied by n, what happens to ΔH?
- ΔH changes signs (either becomes negative or positive)
- ΔH also gets multiplied by n
Who authorized the LAW OF HEAT SUMMATION?
Germain Henri Hess
What does the LAW OF HEAT SUMMATION state?
the enthalpy (heat) change of an overall process is the sum of all heat changes of its individual steps
2nd Law of Thermodynamics (2)
Law of Entropy
“In any spontaneous change, there is always an increase in entropy (disorder)”
+ Change in ENTROPY
Entropy Formula
ΔS = S final - S initial
MEANING:
+ΔS
-ΔS
ΔS = 0
spontaneous
non-spontaneous
at equilibrium
Gibbs Free Energy Formula
ΔG = ΔH - TΔS
MEANING:
-ΔG
+ΔG
ΔG = 0
ΔG°
Exergonic (loss of free energy) + spontaneous
Endergonic (gain of free energy) + nonspontaneous
Equilibrium
STANDARD free energy change (1 atm and 25 °C)
What does GIBBS FREE ENERGY state? (2)
- determines whether a reaction can happen spontaneously
- a state function that depends on the initial and final equilibrium states, not the path taken to get there
Is T in GIBBS FREE ENERGY formula in Celsius or Kelvin
Kelvin
What types of phase changes are considered endothermic and what are considered exothermic?
ENDO = melting (fus), vaporization (vap), sublimation (sub)
EXO = freezing (freez), condensation (con), deposition (dep)
KE and PE behaviour in CC and HC
CC Horizontal line (Phase Change)
- KE constant
- PE decreases
CC diagonal line (no phase change)
- KE decreases
- PE constant
HC is opposite of KE so increase
HEAT CAPACITY vs SPECIFIC HEAT CAPACITY
HC (Extensive) (C) - q/delta T
SHC (Intensive) (Cp) - C/g
FORMULA FOR:
- no phase change
- w phase change
q = m Cp ΔT
q = m ΔH
wherein ΔH = J/g
