Download Chpt6 - Dr. Erdal ONURHAN

Thermochemistry
Some Forms of Energy
- Solar Energy, part of radiant energy. Solar energy comes from
the Sun and is the primary source of Earth’s energy.
- Thermal Energy is due to random motion of atoms and
molecules. It is generally calculated from temperature
measurements. Temperature is not a measure of thermal energy itself.
- Chemical Energy is stored within the structural units of chemical
substances. When a chemical reaction takes place, chemical energy
is released, stored, or converted to other forms of energy.
- Potential Energy is the energy due to the position of an object.
Chemical energy can be considered to be a form of potential energy,
since it is associated with the positions of atoms in the molecules.
- Kinetic Energy is the energy produced by a moving object.
General Chemistry I CHM 111
Dr Erdal Onurhan
Slide 1
Thermochemistry
System-Boundary-Surroundings
The boundary might be imaginary, as in
this case, or real, as in other cases.
General Chemistry I CHM 111
Dr Erdal Onurhan
Slide 2
Thermochemistry
Three Types of Systems
Open: energy an Closed: only
mass can be
energy can be
exchanged
exchanged
General Chemistry I CHM 111
Dr Erdal Onurhan
Isolated: nothing
is exchanged
Slide 3
Thermochemistry
An Example to State Functions – Distance vs.
Displacement
There are many routes between A and B.
The distance covered by the coloured routes
is different from one another. The
displacement, however, is the same for all
routes, AB.
Displacement is a state function, whereas
distance is not.
General Chemistry I CHM 111
Dr Erdal Onurhan
Slide 4
Thermochemistry
Another Example of a State Function- Volume
General Chemistry I CHM 111
Dr Erdal Onurhan
Slide 5
Thermochemistry
The First Law of Thermodynamics
It is obvious that,
energy lost by the
system is
absorbed by the
surroundings.
Since the
Universe
comprises both
the system and
the surroundings,
energy is
conserved in the
process.
General Chemistry I CHM 111
Dr Erdal Onurhan
Slide 6
Thermochemistry
Sign Convention for Work and Heat
General Chemistry I CHM 111
Dr Erdal Onurhan
Slide 7
Thermochemistry
Expansion of a Gas in a Cylinder
Initial State
General Chemistry I CHM 111
Final State
Dr Erdal Onurhan
Slide 8
Thermochemistry
Bomb Calorimeter
The thermometer is used to
determine t of the reaction.
qcal is calculated from
qcal  Ccal t
General Chemistry I CHM 111
Dr Erdal Onurhan
Slide 9
Thermochemistry
An Open Calorimeter
The thermometer is used to determine t of the
reaction. q is calculated from
q  msT
General Chemistry I CHM 111
Dr Erdal Onurhan
Slide 10