Genie In A Bottle

The magic of Redox.

HOME  | SAFETY  | NEW | TEACHERS | PARENTS | CATEGORIES | LIST | AUTHOR

Purpose -

This demo shows a vigorous redox reaction, but can also be used as a spectacular demonstration of the reaction between starch and iodine. 

Nature - 

Demonstration

Materials - 

1 litre Florence flask, 30% Hydrogen peroxide solution, Sodium iodide or Potassium iodide, a sheet of photocopy paper, stapler, heat mat

Method - 

· Pour about 50 ml of Hydrogen peroxide into the Florence flask.

· Place about 10 gm of  Sodium or Potassium iodide in the centre a square of photocopy paper, and bundle the package so that it can easily fit down the neck of the flask.  Staple if necessary.  Drop the filter paper bundle into the flask and watch the results.

· At first you will note the paper package going a blue then black colour; then the paper gives way and a more vigorous reaction takes place.  This is described a the genie escaping from the bottle.

Safety -

The gases given off are oxygen, steam and small amounts of gaseous iodine; not really harmful but avoid too much inhalation.  There is a great deal of heat given off to give the bottle time to cool before handling. 

Explanation -

A vigorous redox reaction occurs between the aqueous iodide ions and the hydrogen peroxide.  The sodium or potassium ions (depending on the chemical used) are simply spectator ions that do not participate in the reaction.  The equation is simplified as :-

NaI + 2H₂0₂ = 2H₂O + O₂ + Na⁺(aq.) + I^- (aq.)

The blue/black colour that is noted at first is the reaction between the newly aqueous iodine and the starch in the paper packet.

Notes -

Because of the safe by products of this reaction is safe to perform in a well ventilated lab on the from bench.  This always a crowd pleaser.