Chemical Processes and Reactions
, Chapters 4; 16.1-2, 10, 11; 20. 1-2.
(Ch 4) 22, 26, 32, 40, 47, 50; (Ch 16) 1, 18, 26, 102; (Ch 20) 18, 20
(1) Thermodynamics vs. Kinetics
Chemical reactions are typically spontaneous processes over which we try to exert some control
– that is, we try to get them to go faster or slower, to release energy in the form of work or heat,
To understand the fundamental nature of chemical processes, we must utilize concepts in
The most general expression for a chemical reaction is
in which “Conditions” refers to certain characteristics external to the reaction we can control.
the thermodynamic sense, the chemical reaction is the “system,” the environment in which the
reaction occurs is the “surroundings.”
The conditions we can control include temperature,
pressure, amounts of reactants and/or products (typically expressed either as moles or
concentrations, when a reaction occurs in solution), catalysts present, etc.
We can diagram how
a reaction takes place by plotting the concentration of reactants and products vs. time:
(Reaction “goes to completion”)
[n] = concentration of chemical species (M =
moles / liter)
(Reaction establishes chemical equilibrium)
In both cases above, equilibrium is established when the concentrations (amounts) of products
and reactants remain constant in time.
There are two fundamental questions:
(a) What drives a chemical reaction
This question refers to the
of the system,
i.e., concepts including
Gibbs free energy
, which are
critical for understanding
like precipitation of a solid or formation of a gas may lead to a spontaneous process.