Chemical Thermodynamics : Hess' Law

Students will study temperature data to verify that the overall enthalpy change for a reaction depends only on the initial and final states of the system and is independent of the reaction pathway between these states (Hess' Law). Students will state Hess' Law in their own words.

Lab Summary:

In this experiment, you will use a Temperature Sensor to investigate the enthalpies of several reactions. Students will analyze their data in order to determine whether their data supports Hess's Law.

Download free labs:

(student versions)

Xplorer GLX-based lab  (PDF, 240 KB)

Computer-based lab  (PDF, 380 KB)

Method:

Use a Temperature Sensor to investigate the enthalpies of several reactions. Analyze the data in order to determine the importance of Hess's Law.

Here's What You Need:

Required for Xplorer GLX-based lab:

(See lab download for computer-based lab requirements, which may differ)

Probeware

• PASPORT Stainless Steel Temperature Probe (PS-2153)
• Xplorer GLX Graphing Datalogger (PS-2002)
  (or alternate PASPORT interface -- see other options)

Other Materials

• Small Tripod Base & Rod (SE-9451)
• Buret Clamp (SE-9446)
• Balance (SE-8756A)
• Magnetic Stirrer (SE-7700)
• Beaker, 250 mL
• Graduated cylinder, 100 mL
• Spatula and/or tweezers
• Styrofoam cup
• Weighing paper
• 1.0 M Hydrochloric acid (HCl)
• 0.5 M Hydrochloric acid (HCl)
• 1.0 M Sodium hydroxide (NaOH)
• Sodium hydroxide (NaOH), solid
• Water, distilled

Lab Manual:

The computer-based activity is included in Explorations in Chemistry (PS-2808). The Xplorer GLX-based lab is included in Chemistry with the Xplorer GLX (PS-2819A). Both manuals are complete with Teacher Information pages, student instructions and handouts, and sample data.

For your convenience, we offer bundles which provide the probeware for the activities in the manual. For more, please see:
Computer-based Chemistry Lab Manual and Bundles
Xplorer GLX-based Chemistry Lab Manual and Bundles