Experiment 4

Objectives:  Catalysis, Equilibrium, and Le Chatelier's Principle

Introduction:

This experiment demonstrates the principles of catalysis and equilibrium, with particular emphasis on Le Chatelier's Principle, which explains how systems at equilibrium respond to changes in concentration, temperature, or pressure.

Chemicals:

Acetic acid (100%)1-ButanolConcentrated sulfuric acidCobalt (II) chloride hexahydrate (CoCl₂ · 6 H₂O)Ethanol

Apparatus and Glassware:

Magnetic stirrer hotplateMagnetic stirring barWater estimation apparatus (Dean & Stark) with stopcock, consisting of:Flat-bottom flaskReflux condenserGraduated receiver with glass stopcock (19/26 sockets & 24/29 cone)Test tube

Experimental Procedure:

1.    Set up the apparatus with a flat-bottom flask (1), Dean-Stark trap (2), and reflux condenser (3).

2.    Place the following chemicals into the bottom flask:

o   25 mL of 1-butanol

o   15 mL of acetic acid

o   1 mL of concentrated sulfuric acid

o   A few boiling stones

3.    Using the hotplate, heat the reaction mixture to boiling.

4.    As the reaction proceeds, vapors ascend to the reflux condenser, where they condense and drip into the Dean-Stark receiver. The condensed liquid separates into two immiscible layers (interface).

5.    The bottom layer is allowed to flow into a test tube containing a blue solution of cobalt(II) chloride in ethanol.

Observation:

Upon adding the condensed liquid to the cobalt(II) chloride solution, the color of the solution turns pink.

Questions:

1.    What color is formed at the end of the test? The solution turns pink, indicating a shift in equilibrium involving cobalt(II) chloride, which is sensitive to changes in water concentration.

2.    Why is concentrated sulfuric acid used? Concentrated sulfuric acid acts as a catalyst, speeding up the esterification reaction by providing protons (H⁺ ions) and helping to drive the equilibrium towards product formation.

3.    Why is a magnetic stirrer used? A magnetic stirrer ensures uniform mixing of the reactants, helping to maintain consistent heating and interaction between the reactants, improving the reaction's efficiency.