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DEN-MCNEIL STUDENT IAR NOTEBOOK
Note: Insert Divider Under Copy Sheet Before Writing
EXPERIMENT #6: CALORIMETRY
Project:
A new eco-friendly coffee shop has just moved across from campus and is scheduled to open in three
weeks. They had a great idea to use only glass containers for their hot coffee drinks. However, they
were concerned about these containers’ ability to keep the drinks hot. They decided to hire your
consulting team to conduct some experiments to determine if their idea is so great! Your knowledge of
calorimetry will prove to be invaluable.
1. Design and determine the best apparatus for use as a calorimeter
2. Use this apparatus to determine the heat of reaction of a chemical reaction
Background:
Chemical reactions and processes may produce or absorb heat when they occur.
It is of major
importance to the chemist whether heat is absorbed (endothermic) or produced (exothermic) by a
particular reaction and how much heat is produced or absorbed for a given amount of material. The
study of heat transfer during chemical reactions is called thermochemistry.
Typically we are examining reactions occurring open to the atmosphere and therefore at a constant
pressure); we refer to the heat exchanged at constant pressure as the change in enthalpy, delta H.
Thermodynamically, the system is defined as the substance or substances that we are studying in which
a change occurs. For chemical reactions, the system is generally the chemicals involved in the reaction.
The system is in contrast with the surroundings which is everything else in the neighborhood of the
system; this includes the water used as the solvent.
To determine experimentally the amount of heat absorbed or produced during a chemical reaction, we
use a device called a calorimeter (meter = “to measure” and calori = “calories”). We determine the
amount of heat exchanged in a process by measuring changes in temperature for the immediate
surroundings which are insulated from the rest of the universe. Because the cups are open to the
atmosphere, any reaction carried out in the cups is done at constant pressure and the amount of heat
exchanged will be the enthalpy change, delta H.
In order to determine how much heat is exchanged based on a temperature change, we must also know
the heat capacity of the material for which we are measuring the change in temperature. The amount of
heat exchanged is equal to the heat capacity of the material times the change in temperature: q = CX
??.
Techniques:
Laboratory: measuring mass and volume, recording temperature
Computer: apparatus setup using ChemSketch (do not cut and paste from this document), excel
for data table and graphing
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H
outside of the test tube (careful; it is hot), and transfer the piece of metal into the calorimeter
containing 50 mL of water without splashing any water out of the calorimeter. Measure the
temperature at 30 second intervals for 3 minutes. What is the system? What is the surroundings?
Analysis of experiment using chemistry drawing software.
Draw the calorimeter after the metal has been added using the chemistry drawing software; include the
compounds in the calorimeter. What is the system? What is the surroundings?
metal
Analysis of the metal through calculations.
From your experimental data, the amount of heat gained by the water for the entire process (not for
each temperature increment) can be calculated for each apparatus. If this is the heat gained by the
water, what is heat loss by the metal? Using Excel, plot temperature vs. time. From this graph, you will
gain information that will either support or refute your previous decision regarding the appropriateness
of each designed apparatus.
Calculate the heat capacity of metal from its heat loss for each apparatus. You will be given the known
value of the heat capacity for your unknown metal once you have completed your calculations.
Compare this value with your values determined experimentally and discuss. This should be the final
data that will assist in determining the most appropriate calorimeter for use in a chemical reaction.
Use of the designed calorimeter to determine the heat of reaction of a neutralization reaction.
Add 50.0 mL of 2.0 M HCl solution into the calorimeter. Carefully rinse out your measuring tool with
distilled water, and measure out 50.0 mL of 2.0 M NaOH solution. Check to make sure that the two
solutions are within 20.5°C of each other. Use the average temperature of the two solutions as your
initial temperature, Ti. Be sure to carefully rinse and wipe off the thermometer between measurements
to avoid pre-mixing the solutions. Once the solutions are at the same temperature (within 10.5°C) put
the thermometer in the HCl solution in the calorimeter and quickly add the NaOH solution. Use the
thermometer to gently stir the resulting solution and measure the maximum temperature that is
achieved; this is Tf. What is the system? What is the surroundings?
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EXPERIMENT #6: CALORIMETRY
Group Experimental Design Pre-lab
1. Design two unique calorimeters. The calorimeters will be judged on originality (no coffee cup
calorimeters from online will get you the prize!), creativity, potential effectiveness, and how
well it addresses the concerns of the coffee shop in your project. Some items available are:
styrofoam cups, beakers (many sizes), aluminum foil and whatever else in the lab your instructor
approves!
2. Write a detailed experimental procedure. This procedure should be written stepwise with the
initials of the student who is performing that step in the procedure. Here is an example:
1. Weigh substance- AW (these are the initials of student performing task)
2. Get the volume of substance – EE
3. etc.
Somos
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