Energy and Rates Analysis of Chemical Reactions

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                                                                                        Unit 3 Lab:

Lab 3: Energy and Rates Analysis of Chemical Reactions

Name: Alec Cooke

Partners: Erik MacPherson and Ben Murat

Experiment Date: November 6th 2008.

Lab 3:

Energy and Rates Analysis of Chemical Reactions

Due Date: November 17th 2008.

Instructor: Mr. MacLean


  1. How does the molar enthalpy of reaction of magnesium vary with different acids, namely, hydrochloric, sulfuric, and acetic acids?
  2. How does the rate of reaction of magnesium vary with these acids?


If magnesium is mixed into any of the aqueous acid solutions, it is predicted that there will be fizzing and bubbling.  This bubbling will be due to the release of Hydrogen gas, which is produced when the hydrogen bonds are broken and replaced with the magnesium.  

It is hypothesized that the test tubes will be warm, because the reaction is exothermic; therefore it releases energy, or heat into its surroundings.  It is also expected that the carboxylic acid (Ethanoic acid) will have a faster rate of consumption for magnesium, because its carbon base will allow it to let go of its hydrogen atoms more readily than hydrochloric and sulfuric acid.

The molar enthalpy for Magnesium should only vary because of human error.  All three calculated enthalpies should be very close, because the molar enthalpy of Magnesium is dependant upon only Magnesium's properties, not the other reactants'.


  • 1 mol/L Aqueous Ethanoic acid
  • 1 mol/L Aqueous Hydrochloric acid
  • 1 mol/L Aqueous Sulfuric acid
  • Magnesium shavings
  • 3 calorimeters
  • 3 stop watches
  • Three 50mL graduated cylinders
  • Three 100mL beakers
  • Digital scale
  • Safety glasses


  1. Apply safety glasses, and gather all apparatus.
  2. Using the digital scale, measure out three samples of approximately ¼ g of magnesium.  Be sure to record the exact mass of each sample.
  3. Measure out 50mL of each aqueous acid using the graduated cylinders.  Using the digital scale, measure and record the mass of each sample.
  4. Transfer each sample into separate, labeled calorimeters.
  5. Using the thermometer, measure and record the temperature of each acid sample.
  6. Add one of the ¼ g samples of magnesium to each calorimeter, and immediately put the lid on the calorimeter on to close the system.  Each person in the group will watch a calorimeter, and record the highest temperature that it reaches.
  7. Pour the products down the drain of a functioning sink.  Wash calorimeter and thermometers.
  8. Repeat steps 2 and 3.  
  9. Transfer each sample of aqueous acid into a separate, labeled 100mL beaker.  Ensure that each acid is at approximately the same temperature.  
  10. Prepare the three stopwatches.  
  11. Add a sample of Magnesium to each beaker (be sure to record the exact mass of magnesium being added to each), and simultaneously start the stopwatches.
  12. When the magnesium is completely dissolved in the first solution, stop the first watch.  When the magnesium in the second solution is completely consumed stop the second watch, and when the last one has no visible magnesium left, stop the final watch.  Record the three times.  
  13. Again, dispose of the products in the drain of a sink, and wash all apparatus.
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Enthalpy test:

Rate test:


Q: How does the molar enthalpy of reaction of magnesium vary with different acids, namely, hydrochloric, sulfuric, and acetic acids?

A: The three molar enthalpies were all relatively close.  The difference between the enthalpies is most likely due to human error, or other complications during the experiment.  Such as the inaccuracy of the scale, thermometer, calorimeter or any other apparatus used.  A major source of error could have been using the specific heat capacity for water for each acid.  Ideally the three molar enthalpies should be ...

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