CHEM 403 Fall 2018
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Thermochemistry
Goals and Challenges:
The following experiments concern heat: heat flow, heat production and the relationship with
bond breaking and bond making. In Part I, you will study heats of dissolution; in Part II, you
will model the relationship between heat and bond breaking and making and will then determine
the heat of combustion of methanol via calorimetry.
Bring to lab:
Lab notebook
Safety eyewear, lab
coat, closed-toe
shoes, long pants
Calculator
Pre-lab work (in your lab notebook):
Short summary of the experiment
Written pre-lab assignment (see below)
Procedural outline to be followed during lab,
including the data table for Part I and data
sheet for Part IIB
Pre-laboratory Assignment
Write the following in your laboratory notebook immediately after the short summary of the
experiment. You will tear out the perforated pages and turn them in at the beginning of the lab.
Read Appendix D – Using a Coffee-Cup Calorimeter posted on myCourses along with this
handout. This will help you understand the meaning of system and surroundings needed to
answer the questions below.
1. In Part I of this lab, you will be dissolving various salts (ionic compounds) in water. A
temperature change may or may not be observed; a temperature change indicates that heat is
produced or absorbed by the system and flows to or from the surroundings during the
dissolution. For the dissolution of NaCl, what is the system?
a) NaCl(s)
b) NaCl(s), Na+(aq), Cl-(aq)
c) NaCl(s), Na+(aq), Cl-(aq), water, container
d) Container and water
e) Water only
2. For the above system, what is/are the surroundings?
a) NaCl(s)
b) NaCl(s), Na+(aq), Cl-(aq)
c) NaCl(s), Na+(aq), Cl-(aq), water, container
d) Container and water
e) Water only
CHEM 403 Fall 2018
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3. In your own words, state the Law of Conservation of Energy as it applies to dissolution
reactions.
4. In the calorimetry experiment (Part IIB), identify the system.
a. Reactants
b. Reactants and products
c. Reactants, products, water, and calorimeter
d. Water and calorimeter
e. Calorimeter only
f. Water only
5. In the calorimetry experiment (Part IIB), identify the surroundings
a. Reactants
b. Reactants, products, water, and calorimeter
c. Water and calorimeter
d. Calorimeter only
e. Water only
6. If heat is produced by a chemical reaction, what happens to the temperature of the
surroundings?
a. decreases
b. increases
c. stays the same
d. cannot be determined
7. If heat is required for a chemical reaction to occur, where does the energy come from?
a. from the chemical reaction itself
b. from the surroundings
c. from the chemicals
d. from the reactants
8. If heat is removed from the surroundings of a chemical reaction, what happens to the
temperature of the surroundings?
a. decreases
b. increases
c. stays the same
d. cannot be determined
CHEM 403 Fall 2018
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LABORATORY PROCEDURE
PART I: HEAT OF DISSOLUTION
Your TA will assign different salts to different pairs/groups. Divide up ...
