Exam 2 ch 9 Flashcards
First law of thermodynamics
-Total energy of the universe is constant
-Energy cannot be created or destroyed
Energy
-Ability to do work or supply heat
Kinetic energy
-Energy of motion
Potential energy
-Stored energy in bonds
Bond forming diagram
- As 2 atoms get closer together PE goes down
-Optimal bond distance, PE at min, stable - Repulsion goes up when atoms overlap too much, E required to break, not stable
Kinetic energy and temperature
-As KE increases, so does temp
-Temp is how fast particles are moving
-They are directly related
System
-Starting reactant and product
Surroundings
-Flask
-Room
-Building
-Universe
Heat capacity
-Amount of heat required to raise the temperature of an object 1 degree C
Specific heat
-Amount of heat required to raise 1 gram of a substance by 1 degree C
Molar heat capacity
-Amount of heat required to raise one mole of a substance by 1 degree C
Specific heat/Heat capacity equation
q = mc^T
Units J/ gC
q = heat absorbed/released
m = grams
c= specific heat
^T = Change in temp C
Heat capacity is same thing without grams
Heat and temperature different
-Because heat is total energy transferred, depends on mass
-Temp is how fast particles move
Enthalpy
-Delta H or q
-Total heat of a system at constant pressure
-Measured in open system
-Heat flowing out of the system has - sign
-Heat flowing into the system has + sign
Internal energy
-E
-Delta E rxn = Efinal-Einitial
-Measured in closed system
-kinetic + potential energy
TOTAL INTERNAL ENERGY = Delta U
A way to lose/gain energy
Lose: Push against a constant atmospheric pressure
Gain: Contract as atmosphere presses in on the system
Work equation
-P^V
P = Pressure (always + before)
Delta V = Change in volume (Vfinal-Vinitial)
-Inversely related
-Work is contractions/expantions
Coffee cup calorimetry
-Insulated
-Measure temp rise in the cup
-Temp rise related to how much heat is given off
-q=mc^t
-Delta H = q
- q of water
- convert to kJ
- divide by moles
Bomb calorimetry
-Combustion reactions
-Reaction and bomb heat up
-Bc volume is constant and not pressure, E = H
H=q
qcal = ccal * ^Tcal
- q of water
- q of bomb
- add
- Convert to kJ and if need moles, divide
Coffee cup vs bomb
-Use coffee cup when want constant pressure
-Use bomb when want constant volume and high energies
How are delta E, H, and P^V related
Delta H = Delta E + P^V
Enthalpy is equal to internal energy plus the work on the system
2 ways a system can lose energy
-Heat
-Work
Heat, work, energy equations
^E = q-P^V
Work = -P^V
^E = work + q
^H = ^E +P^V
^H=q(p)
When would delta E and delta H not be close in value
-Big volume changes
-Phase changes that lead to bigger volumes
-Extreme work being done
