Equilibrium investigations and the synthesis of a biobased ink

Laboratory Procedures (PDF)

Author Contact: douskey@berkeley.edu

Summary

This experiment takes a qualitative approach to equilibrium chemistry, studying Le Chatelier’s principle as it applies to the synthesis of bio-based ink.

Students performed experiments in 3 separate investigations. In the first, they mixed copper sulfate and sodium carbonate, and then added vinegar to the mixture to study solubility rules and precipitation: a blue solid, copper (II) carbonate formed. In the second, they studied acid-base equilibria by creating a color gradient using indicators and solutions of various pH. They then use the gradient to identify the pH of an unknown solution. The third investigation dealt with redox equilibria: manipulating the equilibrium of oxygen to synthesize a bio-based ink from iron sulfate, tea/oak galls, ascorbic acid, and hydrogen peroxide.

This exercise gave students a chance to see the applications of equilibrium chemistry, rather than just mixing various solutions and waiting for precipitation. It demonstrates the Green Chemistry principle s of renewable feedstocks. It is also a greener alternative to traditional experiments that use heavy metals like Cd, Pb, Hg, and Cr.

Summary prepared March 2012 by Swetha Akella at the UC Berkeley.

Category Descriptors

Chemistry Concepts

• Aqueous Solution Chemistry
• Equilibrium
• Lewis Acids/Bases
• Oxidation/Reduction Chemistry
• Qualitative Analysis
• Solutions/Solvents

Laboratory Techniques

• pH

Green Chemistry Principles

• Design Safer Chemicals and Products
• Prevent Waste
• Use Renewable Feedstocks
• Use Safer Solvents/Reaction Conditions

Chemistry Subdiscipline

• Analytical Chemistry

Target Audience

• Colleges/Universities

Source

• Original Contributions - unpublished