S150: Chemical Rxns – Crystallization – Saturated Sodium Acetate

Introduction

A seed crystal can be dropped into a saturated solution of sodium acetate.  The solution will suddenly crystallize and turn to solid.  Alternately, the solution may be slowly poured out onto a seed crystal on a flat surface.  The solution will crystallize as it touches the crystal, resulting in an increasingly tall tower of sodium acetate.

NaC₂H₃O₂(aq) → NaC₂H₃O₂ • xH₂O(s) + ∆

To Conduct Demonstration

1. Carefully drop a seed crystal into a flask of saturated sodium acetate.  Solution will immediately crystallize into a solid and give off a large quantity of heat.

      Or

2. Place a seed crystal of sodium acetate on a board or flat piece of plastic.  Slowly pour saturated sodium acetate solution onto the crystal.  A tower of crystallized sodium acetate will grow upwards.

Note:  Please be aware that, even with the greatest care, saturated sodium acetate solutions are prone to crystallize spontaneously.  The farther the flasks are carried, the greater the risk.

Demo Time: ~? minutes

Safety 

Dispose in the appropriate waste container 

Reference

B. Shakhashiri, Chemical Demonstrations Vol. 1, p 27, 1992.

Acknowledgment

Margaret Asirvatham, Spring 1995
Lora Ruffin and Michael Polk, Summer 2009