Chemistry

1. Energy
 Potential energy: Is
STORED energy.
Example energy stored
in a bond.
When bonds are broken
:Energy is required.
When bonds are created
:energy is released.
 Kinetic energy: Is
associated with
motion.
Example ,A moving car.

2. Heat of reaction(Enthalpy Change)
 Endothermic reaction
Heat is absorbed by the
system.
H >0
 Exothermic reaction
Heat is released to
surrounding.
H<0
Video on
exothermic and
endothermic
reactions

3. Entropy
 Degree of randomness or disorder in the system.
 Video on entropy

4. Spontaneous reaction
 Factors that predict spontaneity
 Enthalpy Change
 Entropy change
 Both these factors are brought together by Gibb’s
free energy equation:
 G = H - T S
 Video on Spontaneous reactions

5. Problem 1:
 1. Predict an increase or decrease in entropy.
(Remember, increase in entropy is when disorder
or randomness increases !!)
 (a) Assembling a jigsaw puzzle.
 (b) Constructing a building from loose bricks.
 ( c) CaCO3(s)  CaO(s0 + CO2(g)

6. Problem 2 :
 Calculate change in Gibbs free energy and predict
if the reaction is spontaneous or not for a
reaction which has H = +16.3Kcal/mol
and S = 2.3cal/(mol.K) at 300K.

7. Problem 3
 Explain the following statement.
All exothermic reactions are spontaneous at all
conditions of temperature but ,spontaneity of
endothermic reaction depends on change in entropy
and temperature.