Introduction

Isopropyl alcohol is added to dark green crystals in a crucible or on a candle.  Flames are produced, igniting the candle wick.

Equations

2CrO3 + 3(CH3)2CHOH  3(CH3)2CO + Cr2O3 + 3H2O

Isopropyl alcohol is oxidized to acetone by the chromium trioxide.  Heat given off by the reaction ignites the acetone.

Prior to Lecture  

  1. Assemble the following: 
    •  crucible (or crucibles) containing about 1g of CrO3
    • candle with a small amount of CrO3 in a hollow next to the wick
    • isopropyl alcohol in dropper bottle
    • fire extinguisher

To Conduct Demonstration

  1.  Drop isopropyl alcohol (from a height of about 18") into a crucible containing about a gram of CrO3 or onto a candle with CrO3 crystals next to its wick.

Safety and Disposal

Keep the dropper bottle of alcohol a safe distance from any flames.  Perform on a heat-proof surface.  Chromium compounds are carcinogenic and should be handled with care.