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
