Sucrose inversion by polarimetry template

Polarimeter with a 1 dm tube of the reacting solution, the mixture in a flask in a thermostat bath, and a stopwatch. University physical kinetics; IB / A-level extension.

What the template shows

• Follow the acid-catalysed hydrolysis of sucrose by its optical rotation
• Sucrose + HCl, 25 °C
• e.g. 20% sucrose mixed 1 : 1 with 4 M HCl in a thermostat bath; start the clock at mixing
• Rate constant
• α∞ after 48 h (or 15 min at 60 °C). Plot ln(αt − α∞) against t: slope −k (pseudo-first order, water in excess)
• Sodium lamp, 589 nm
• Light passes a polariser, the tube, then the analyser
• Polarimeter tube, 1 dm
• Fill bubble-free from the flask; any bubble goes in the bulge. Rotation falls from + to − as fructose forms
• Analyser and scale
• Turn to equal half-shades and read α every few minutes; zero with water first
• Reaction setup

Drawn with 12 shapes – every one editable in MolDraw.

Sources

• Atkins, de Paula & Keeler, Atkins' Physical Chemistry, 11th ed., OUP 2018 Textbook