Types of Calorimeters
Objective
lesson 9
chapter 9
You will be able to
· Identify the type of calorimeter as either a flame or
bomb calorimeter.
· Perform calculations to determine the change in
enthalpy for a reaction in each type of calorimeter.
Flame Calorimeter
This is used to measure the heat energy produced in a
combustion reaction.
Qsurroundings = ∆Hsystem
mc∆t (water) + mc∆t (calorimeter)=n∆ H
c
Example 1
In a flame calorimeter the combustion of 0.35 g of ethanol causes
the temperature of 363 mL of water to increase 6.30˚C. The mass
of the aluminum calorimeter is 11.0 grams and it undergoes the
same temperature change. What is the molar enthalpy of
combustion for ethanol?
Example 2
The following apparatus can be used to determine the
molar enthalpy of combustion of butan-2-ol.
Initial mass of the burner: 223.50 g
Final mass of the burner : 221.25 g
water
Mass of copper can + water: 230.45 g
Mass of copper can
: 45.60 g
Final temperature of water: 67.0˚C
Intial temperature of water : 41.3˚C
Determine the molar enthalpy of combustion of butan-2-ol.
A bomb calorimeter is used to measure enthalpy changes for
reactions that don’t take place in solution
i.e. a combustion reaction, or any reaction that uses or produces
gases
They are made of materials that can withstand high pressures (so they
don’t explode when gases are produced)
Types of Calorimeters
Water filled (same as video)
The energy from the reaction is transferred to the water
Q(calorimeter) = mc∆t
Ideally the heat capacity of the calorimeter includes those of all parts
including water, thermometer,stirrer and the container.
In these types of examples you will be given a mass of water.
Other Materials
The energy from the reaction is transferred to the materials in
the calorimeter
Q (calorimeter) = C∆t
The heat capacity of the calorimeter is known (C in kJ/˚C)
Example 2
A 1.00 g sample of propane was placed in a bomb calorimeter and
ignited. The initial temperature of the calorimeter was 25.0˚C and
the final temperature was 27.3˚C. If the heat capacity of the
calorimeter is 97.1 kJ/˚C, what is the molar enthalpy of
combustion for propane?
Measuring Energy Content of Foods
(or other Fuels)
The energy content of food can be determined by burning the food in a
calorimeter. Because food is not a pure substance, the energy content
is usually expressed in kJ/gram.
Energy content = heat content = energy per gram = enthalpy per gram
(They all mean the same thing)
A peanut was burned using a flame calorimeter. The following
data was collected:
Mass of peanut before burning
Mass of peanut residue after burning
Mass of water in the calorimeter
Initial temperature of the water
Final Temperature of the water
1.30 grams
0.80 grams
100 grams
21.0 ˚C
32.3˚C
Use this information to calculate the energy content of the peanut in kJ/gram
Assignment
Worksheet Assignment #7