Chapter 5 Thermochemistry Flashcards
Energy
Is the ability to do work or transfer heat
Energy used to cause an object to move is called
Work
Energy used to cause the temperature of an object to rise is called
Heat
Kinetic energy
Energy of an object by virtue of its motion
Potential energy
Energy an object possesses by virtue of its position or chemical composition
The most important form of potential energy in molecules is
Electrostatic potential
El= kQ1Q2/d
SI unit of energy is
Joule
1J=kg m^2/ s^2
1 calorie equals
4.184 joules
Work=
Fxd
1st law of Thermodynamics
Conservation of energy
Internal energy
Is the sum of all the kinetic and potential energy of the system
E
deltaE=
Efinal-Einitial
If deltaE is greater than zero
Energy change is endergonic
When energy is exchanged with the surroundings it is exchanged as either
Heat or Work
deltaE= q+W
Sign conventions for q, w, and delta E
+q means system gains heat
+w means work done on system
+deltaE means net gain of energy by system
When heat is absorbed by the system process is
Endothermic
The internal energy of a system is independent
Of the path by which the system achieved that state
State function
Depends only on the present state and not the path
q and w are not
State functions
Work volume equation
W=-P x deltaV
Enthalpy
Is the internal energy plus the product of pressure and volume
H=E + PV
deltaH= =deltaE + P x deltaV
At constant pressure the change in enthalpy is
The heat gained or lost
deltaH = q
When deltaH is positive
Endothermic
deltaH =
Hproducts-Hreactants
dH is called
Enthalpy of reaction or heat of reaction
Enthalpy is a ________ property
Extensive
Calorimetry
Measurement of heat flow
Amount of energy required to raise the temp of a substance by 1 deg K is its
Heat capacity
Specific Heat
Amount of energy to raise the temp of 1 gram of a substance by 1 deg K
Hess’s Law
States that if a reaction is carried out in a series of steps, dH for the overall reaction will be equal to the sum of the enthalpy changes for the individual steps
Enthalpy of formation
Is the enthalpy change for the reaction in which a compound is made from its constituent elements in their elemental form
