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
The two most common forms of carbon,
diamond and graphite, are typically
In diamond, the hardest naturally occurring
substance, each carbon atom is surrounded
by a tetrahedral arrangement of other carbon
The structure of grap
Can you write reactions?
Hydrochloric acid is added to a solution of
Solutions of cobalt (II) nitrate and sodium
hydroxide are mixed.
Solid calcium sulfite is heated in a vacuum.
Sodium and nitrate are spectator ions so the
net ionic equation is
Ba2+(aq) + SO4-(aq)
We use the equation: q
We first need to find the mass of solution
The total volume of solution is 2.0 L, so
Bond Polarity & Dipole
Moment of positive
A molecule that has a center
charge and a center of negative charge is
said to be dipolar, or to have a dipole
Leading to a Polar
leading to a
Chapters 8 & 9
A chemical bond is a force that holds two
or more atoms together.
The strength of a chemical bond can be
obtained by analyzing its bond energy,
which is the energy required to break the
A bond will form if the e
Orbital Filling Sequence
Ionization energy is the energy required
to remove an electron from a gaseous
atom or ion.
The first ionization energy is the energy
required to remove the highest energy
electron of an
= hc =
(6.626 x 10-34)(3 x 108)
1.633 x 10-18
= 1.216 x 10-7 m
Sample Calculation # 4
How much energy is required to remove
the electron from a hydrogen atom in its
Solution: Removing the electron from a
hydrogen atom in its ground state
We need to use the equation: E = h
So first, we must find the frequency of the
= c = 3.00 x 108 m/s = 6.66 x 1014 Hz
4.50 x 10-7 m
Now plug into the original equation.
E = (6.626 x 10-34 J/Hz) x (6.66 x 1014
The next i
Radiant energy that exhibits wavelike
behavior and travels through space at
the speed of light in a vacuum.
Wavelength () is the distance between
two consecutive pea
Acids and Bases
Acids produce hydrogen ion when
dissolved in water.
Bases produce hydroxide ion when
dissolved in water.
This concept is too limited because it only
applies to aqueous solutions and allows
for only one kind of
Calculating Ka from %
A 0.15 M solution of a weak acid is 3.0%
dissociated. Calculate Ka.
Calculating the pH of a Weak
Calculate the pH for a 15.0 M solution of
ammonia (Kb = 1.8 x 10-5).
Acids that can furnish more than
Acids and Bases are defined as follows:
An acid is a proton donor.
A base is a proton acceptor.
HCl donates a hydrogen (proton) to water making
it an acid.
Water gains a hydrogen
The Common Ion Effect
When you have a solution containing a
weak acid and its salt there will be a
The addition of F- from the salt will cause
the acid equilibrium to shift to the left du