ENTHALPY Flashcards
(32 cards)
It defined work as directed energy change resulting in process
Chemistry
It is a solar energy, comes from the sun and is earth’s primary energy source
Radiant energy
Energy associated with the random motion of atoms and molecules
Thermal energy
Energy available by virtue of an objects position
Potential energy
The transfer of energy between two bodies that are at different temperatures
Heat
The study of heat change in chemical reactions
Thermochemistry
It is stored within the structural units of chemical substances
Chemical energy
- It is the specific part of the universe that is of interest to us
- The rest of the universe outside the system
System
Surrounding
Energy changes in chemical reactions
1. Can exchange mass and energy, usually in the form of heat with its surroundings
2. Allows the transfer of heat energy but not mass
3. Does not allow the transfer of either mass or energy
Open system
Closed system
Isolated system
Properties that are determined by the state of the system, regardless of how that condition was achieved (Ex: Energy, pressure, volume and temperature)
- It does not matter if the process is fast or slow, the end points matter than the obstacles.
State functions
The energy can be CONVERTED from one form to another but cannot be CREATED or DESTROYED
• We can test the validity by measuring only the change in internal energy of a system between its initial state and its final state in a process
∆U = Uf - Ui
The first law of thermodynamics
In chemistry, we are normally interested in the ___ (which may be a flask containing reactants and products) not with its surroundings
Energy changes associated with the system
- It is the energy that is transferred from one body to another as the results of a difference in temperature
- It is the energy transferred or from an object via the application of force along a displacement
Heat (q)
Work (w)
Combustion engine is an example of this work, wherein the gas pushes the piston upward against a constant opposing external atmospheric pressure (P.) The work done by the gas on the surrounding is
w= - P∆V
Mechanical work
The unit of work done by or on a gas are ?
• to express the work done in the more familiar unit of what?
We use the conversion factor:
1 L • atm = ?
Liter atmosphere
Joules
101.3 J
When a process occurs at constant pressure, the ___ evolved (either released or absorbed) is ___ to the change in entalphy
Heat
Equal
It is the sum of the interal energy (U) and the product of pressure and volume (PV)
H= U + PV
Entalphy
If temperature and pressure remain constant through the process and the work is limited to pressure - volume work, then the entalphy change is given by what equation?
∆ H= U + P∆V
SIGN CONVENTIONS FOR WORK & HEAT
- Work done by the system ON THE sorroundings (papalabas mula sa system).=
- Work done ON THE SYSTEM by the sorroundings (papasok ng system) =
- +
SIGN CONVENTIONS FOR WORK & HEAT
- Heat absorbed by the system FROM THE SURROUNDINGS (endothermic process) =
- Heat absorbed by the sorroundings FROM THE SYSTEM (exothermic process) =
• For gas expansion (work done on the system)
∆ V > 0
So - P∆ V is a ___ quantity
• For gas COMPRESSION (work done on the system)
∆ V > 0
So -P ∆V is a ___ quantity
Negative
Positive
Pag expand=
Pag compressed =
- +
When a process occurs at constant pressure, the heat evolved (either released or absorbed) is equal to the change in ____?
Entalphy
Symbol for entalphy
ENTALPHY (H) is the SUM of the INTERNAL ENERGY and the product of PRESSURE and VOLUME
H= U + PV
