Energetics of Chemical Reactions

Energetics of Chemical Reactions


Module by: John S. Hutchinson

The Foundation

We begin our study of the energetics of
chemical reactions with our understanding of mass relationships,
determined by the stoichiometry of balanced reactions and the
relative atomic masses of the elements. We will assume a conceptual
understanding of energy based on the physics of mechanics, and in
particular, we will assume the law of conservation of energy. In
developing a molecular understanding of the reaction energetics, we
will further assume our understanding of chemical bonding via
valence shell electron pair sharing and molecular orbital
theory.

Goals

The heat released or consumed in a chemical
reaction is typically amongst the most easily observed and most
readily appreciated consequences of the reaction. Many chemical
reactions are performed routinely specifically for the purpose of
utilizing the heat released by the reaction.

We are interested here in an understanding of
the energetics of chemical reactions. Specifically, we wish to know
what factors determine whether heat is absorbed or released during
a chemical reaction. With that knowledge, we seek to quantify and
predict the amount of heat anticipated in a chemical reaction. We
expect to find that the quantity of heat absorbed or released
during a reaction is related to the bonding of the molecules
involved in the reaction.

Prior to answering these questions, we must
first answer a few questions regarding the nature of heat. Despite
our common familiarity with heat (particularly in Houston), the
concept of heat is somewhat elusive to define. We recognize heat as
"whatever it is that makes things hot," but this definition is too
imprecise to permit measurement or any other conceptual progress.
Exactly how do we define and measure heat?Energetics of Chemical Reactions



Module by: John S. Hutchinson





The Foundation

We begin our study of the energetics of
chemical reactions with our understanding of mass relationships,
determined by the stoichiometry of balanced reactions and the
relative atomic masses of the elements. We will assume a conceptual
understanding of energy based on the physics of mechanics, and in
particular, we will assume the law of conservation of energy. In
developing a molecular understanding of the reaction energetics, we
will further assume our understanding of chemical bonding via
valence shell electron pair sharing and molecular orbital
theory.

Goals

The heat released or consumed in a chemical
reaction is typically amongst the most easily observed and most
readily appreciated consequences of the reaction. Many chemical
reactions are performed routinely specifically for the purpose of
utilizing the heat released by the reaction.

We are interested here in an understanding of
the energetics of chemical reactions. Specifically, we wish to know
what factors determine whether heat is absorbed or released during
a chemical reaction. With that knowledge, we seek to quantify and
predict the amount of heat anticipated in a chemical reaction. We
expect to find that the quantity of heat absorbed or released
during a reaction is related to the bonding of the molecules
involved in the reaction.

Prior to answering these questions, we must
first answer a few questions regarding the nature of heat. Despite
our common familiarity with heat (particularly in Houston), the
concept of heat is somewhat elusive to define. We recognize heat as
"whatever it is that makes things hot," but this definition is too
imprecise to permit measurement or any other conceptual progress.
Exactly how do we define and measure heat?From: http://cnx.org/content/m12594/latest/