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Calorimetry Paper & Exercise

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Calorimetry
Calorimetry, derived from the Latin calor meaning heat, and the Greek metry meaning to measure, is the
science of measuring the amount of heat. All calorimetric techniques are therefore based on the
measurement of heat that may be generated (exothermic process), consumed (endothermic process) or
simply dissipated by a sample. There are numerous methods to measure such heat, and since calorimetry's
advent in the late 18th century, a large number of techniques have been developed. Initially techniques were
based on simple thermometric (temperature measurement) methods, but more recently, advances in
electronics and control have added a new dimension to calorimetry, enabling users to collect data and
maintain samples under conditions that were previously not possible.
Any process that results in heat being generated and exchanged with the environment is a candidate for a
calorimetric study. Hence it is not surprising to discover that calorimetry has a very broad range of
applicability, with examples ranging from drug design in the pharmaceutical industry, to quality control of
process streams in the chemical industry, and the study of metabolic rates in biological (people included)
systems. Indeed if the full range of applications were to be mentioned, the allocated disk space on this site
would soon be used up.
Calorimeter
A calorimeter is a device used to measure heat of
reaction. It can be sophisticated and expensive or simple
and cheap. A Styrofoam cup can be used as a calorimeter,
because it is a container with good insulated walls to
prevent heat exchange with the environment. In order to
measure heats of reactions, we often enclose reactants in
a calorimeter, initiate the reaction, and measure the
temperature difference before and after the reaction. The
temperature difference enables us to evaluate the heat
released in the reaction. This page gives the basic theory
for this technique.
A calorimeter may be operated under constant (atmosphere) pressure, or constant volume. Whichever kind
to use, we first need to know its heat capacity. The heat capacity is the amount of heat required to raise the
temperature of the entire calorimeter by 1 K, and it is usually determined experimentally before or after the
actual measurements of heat of reaction.
The heat capacity of the calorimeter is determined by transferring a known amount of heat into it and
measuring its temperature increase. Because the temperature differences are very small, extreme sensitive
thermometers are required for these measurements.

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The Bomb Calorimeter
For combustion reactions, we often enclose all
reactants in an explosive-proof steel container,
called the bomb whose volume does not change
during a reaction. The bomb is then submerged in
water or other liquid that absorbs the heat of
reaction. The heat capacitor of the bomb plus
other things is then measured using the same
technique as other calorimeters. Such an
instrument is called a bomb calorimeter, and its
application is called the bomb calorimetry.
Since volume does not change, a bomb
calorimeter measures the heat evolved under
constant volume, q
v
,
q
v
= C * dT,
where dT is the temperature increase. The q
v
so measured is also called the change in internal energy, dE.
Note that
dE = q
v
= C * dT
Other Types of Calorimeter
There are many kinds of calorimeters, each designed for measuring the heat released by a particular
chemical process.
Flame Calorimeter
The combustible gas is metered into the
calorimeter. Temperatures of all reactants must
be controlled. Since the reaction occurs at
constant pressure,
comb
H is measured directly.

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Calorimetry Calorimetry, derived from the Latin calor meaning heat, and the Greek metry meaning to measure, is the science of measuring the amount of heat. All calorimetric techniques are therefore based on the measurement of heat that may be generated (exothermic process), consumed (endothermic process) or simply dissipated by a sample. There are numerous methods to measure such heat, and since calorimetry's advent in the late 18th century, a large number of techniques have been developed. Initially techniques were based on simple thermometric (temperature measurement) methods, but more recently, advances in electronics and control have added a new dimension to calorimetry, enabling users to collect data and maintain samples under conditions that were previously not possible. Any process that results in heat being generated and exchanged with the environment is a candidate for a calorim ...
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