PinE energy stored in
PE represents the change potential
the bonds of the products as compared with the bonds of
Energy is required or absorbed when bonds are
Energy is released when new bonds are formed.
In exothermic reactions
Energy is defined as the capacity to do
work or produce heat.
The Law of Conservation of Energy
states that energy can be neither created
or destroyed it can only change form.
Therefore, the energy of the universe is
Most chemical reactions are reversible.
That is, reactants react to form products, but
those products react to form reactants.
A reaction is at equilibrium when the rate
of the forward reaction is equal to the rate
of the reverse re
Sample Problem #3 (Solution
w = -5.0 x 105 L atm
w = -5.0 x 105 L atm x
1 L atm
W = -5.1 x 107 J
E = q + w
E = (+1.3 x 108 J) + (-5.1 x 107 J)
E = 8 x 107 J
Enthalpy, H, is defined as:
H = E + PV
Where E is the internal energy of t
40.68 g C
= 3.3870 mol
5.08 g H
54.24 g O x
= 3.3900 mol
3.3870 mol C = 1.0000 mol C x 2 = 2
5.0400 mol H = 1.5000 mol H x 2 = 3
3.3900 mol O = 1.0000 mol O x 2 = 2
Empirical & Molecular
Chapter 11 Section 4
The empirical formula for a compound is
the formula with the smallest whole
number mole ratio of the elements.
Molecular Formula: C6H12O6
Calculating Empirical F
The reaction in a galvanic cell is always a
redox reaction that can be broken down
into two half-reactions.
Consider the following reaction:
2H+(aq) + Zn(s)
The two half reactions would be:
2H+(aq) + 2eZn(s)
Electrochemistry is best defined as the
study of the interchange of chemical and
It is primarily concerned with two
processes that involve redox reactions:
The generation of an electric curr
Daltons Law of Partial Pressures
A mixture of gases contains 1.5 moles
of oxygen, 7.5 moles of nitrogen and
0.5 moles of carbon dioxide. If the
total pressure exerted is 800 mmHg,
what are the partial pressures of each
gas in the mixture?
Daltons Law o
When the concentrations of NH4+ and
NO2- were doubled the reaction rates
This means the reaction is first order
with respect to each individually. The
rate law is
Rate = k[NH4+][NO2-]
The overall reaction order is the sum
of the exponents f
Half-Life First Order vs
For a second order reaction, t is
dependent on [A]0.
For a first order reaction, t is
independent of [A]0.
For a first order reaction, a constant time
is required to reduce the concentration of
reactant by half, and then by
Kinetics is the area of chemistry
concerning reaction rates.
One of the main goals of kinetics is to
understand the steps by which a reaction
This series of steps is called the reaction
Types of Chemical Reactions
Solutions in which water is the dissolving
medium, or solvent, are called aqueous
Water is the Universal Solvent since it
has the ability to dissolve many differ
Elements are pure substances that
cannot be separated by physical or
There are 91 naturally occurring elements
The rest are synthetic, or man-made in a lab.
Each element has a u