Featured in PASCO’s College Chemistry Instructor Guide

College Chemistry Instructor Guide


College Instructor edition with 36 experiments covering introductory and general chemistry topics.

Chemical Reaction Equilibrium

Lab Summary

Use a colorimeter to determine the equilibrium constant for a chemical reaction.


Students determine the equilibrium constant for a chemical reaction using visible spectroscopy.


Students gain experience conducting the following procedures:

  • Preparing solutions.
  • Using visible spectroscopy to determine the concentration of an absorbing species.
  • Calculating the equilibrium using Beer’s law, known initial concentrations, and the mathematical relationship between the concentrations of the reactants and products.

Sensors / Equipment Used:

PASPORT Colorimeter Sensor


Our PASPORT Colorimeter records all 4 wavelengths simultaneously--no need to guess at wavelength to get a quality measurement.

Materials Used:

Beaker, 50-mL - 2
Test tube, 15-mL - 5
Test tube rack 
Graduated pipet, 10-mL - 2
Pipet bulb 
0.01 M Iron (Fe3+) - 20 mL
0.00300 M Potassium thiocyanate (KSCN) - 20 mL
Deionized water - 40 mL

The Associated Bundle:

Advanced Chemistry Standard Sensor Bundle


Contains the probeware for completing experiments in the College Chemistry lab manual.

Interface Required

This experiment may require software and an interface for data collection.