AP CHEMISTRY – LAB
Calorimetry –Heat of Formation
Purpose: The purpose of this experiment is to explore the use of a constant pressure calorimeter in order to determine
heats of formation. The purpose of this experiment is also to look at the formation of different compounds using HCl acid
as the common reactant. Preparation of 1.0 M solutions from 12 M Hydrochloric acid.
Materials: Two Styrofoam cups w/ lid, thermometer, Reactants (1.0M HCl, 1.0M NaOH, 1.0 M Na2CO3, Mg Ribbon,
Zinc Metal), Lab Handout.
PreLab: Solution preparation: Write the correct procedure and complete the calculation for making 1.000 L of a 1.0 M
HCl solution from the 12.0 M stock solution in the fume hood. Safety considerations must be included in the prelab writeup!
Procedure: GOGGLES ON AT ALL TIMES! NO OPEN FLAMES! BE CAREFUL WITH THE THERMOMETERS!
Have the prelab procedure checked by the teacher and then begin the solution preparation. (Must be performed under
instructor supervision so you must check with the instructor prior to beginning the operation!)
Group 1: Neutralization Reaction – Formation of Water
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Measure out 50 mL of 1.0M NaOH. Pour it into the Calorimeter.
Take initial temperature of the NaOH. Record this info in the data table. (Assume NaOH and HCl have the same Ti)
Measure 50 mL of 1.0M HCl acid.
Pour the HCl into the calorimeter with the NaOH. Gently swirl the calorimeter.
Record the HIGHEST temperature reached as Tfinal.
Repeat this experiment.
Group 2: Metathesis – Formation of Carbon Dioxide
1. Measure 50 mL of 1.0M Na2CO3. Pour the Na2CO3into the calorimeter.
2. Take initial temperature of the Na2CO3. Record in the data table. (Assume HCl and Na2CO3have the same initial
temp.)
3. Measure 50 mL of 1.0M HCl.
4. Pour the HCl into the calorimeter. Gently swirl the calorimeter.
5. Record the HIGHEST or LOWEST temperature reached as Tfinal.
6. Repeat this experiment.
Group 3: REDOX – Formation of MgCl2. Caution – H2 gas released during this reaction.
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Measure and cut 10-15 cm of Magnesium Ribbon. Record the mass in your data table.
Coil the ribbon around a pencil.
Measure 100 mL of 1.0M HCl.
Pour the HCl into the calorimeter. Measure the initial temperature of the HCl. Record in the data table.
Add the Mg ribbon to the HCl in the calorimeter. Gently swirl the calorimeter.
Record the HIGHEST temperature reached as Tfinal.
Repeat this experiment.
Group 4: REDOX – Formation of ZnCl2. Caution – H2 gas released during this reaction.
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Weigh out approximately 7.0 grams of Zinc metal. Record mass in the data table.
Measure 100 mL of 1.0M HCl.
Pour the HCl into the calorimeter. Measure the initial temperature of the HCl. Record in the data table.
Add the Zinc metal to the HCl in the calorimeter. Gently swirl the calorimeter. The reaction will take time and is
not complete until the reaction ends!
5. Record the HIGHEST temperature reached as Tfinal.
6. Repeat this experiment.
Example DATA TABLE – Reaction of HCl and NaOH
Trial 1
Trial 2
Volume of 1.0 M NaOH used
Initial temperature of NaOH (calorimeter)
Volume of 1.0 M HCl used
Initial temperature of HCl
Final temperature reached by calorimeter
Total mass (volume) of mixture
Temperature change, T, of calorimeter
Heat flow, joules
Moles of Water produced
H (kJ / mol H2O)
Mean value of H:
Trial 3 (if needed)
Literature value:
Data Analysis:
Your data analysis write-up will be written into your lab notebook based on the four groups and should include the
following for each group.
 Net ionic equation
 Calculation of the literature values for the heat of formation of the product.
 Limiting reactant calculation (if necessary)
 Heat flow based on the data (calorimetry equation)
 Moles of product formed
 Enthalpy change per mole
You will then write a Post Experimental Comparison Table of group vs. average ΔH and Literature ΔH values. (A quick
glance at the overall results in a clean little table!)
Finally, add (to this analysis section) a Percent Error calculation for the empirical outcome vs. the literature value for each
group.
Normal conclusion with two errors analyzed (make certain the chosen errors actually affect the outcome and that you have
clear Claim of reasonable error followed by providing Evidence for the claim and concluding with Reasoning that links
the evidence to the claim! Most students fall short of linking these together and JUMP to an outcome not supported by
their reasoning discussion.