Hg-1 Chemical Clock A+B

Aim

To demonstrate a cyclic chemical reaction, the Belousov- Zhabotinskii reaction.

Apparatus

  • 3 1L flasks
  • Overhead Projector
  • Disposable pippetes
  • Solution A 0.23M KBrO3 (Potassium Bromate)
  • Solution B 0.31 Malonic acid & 0.059M (Potassium Bromide)
  • Solution C 0.019M ammonium cerium (IV) nitrate & 2.7M sulphuric acid
  • Solution D 0.025M ferrion sulfate

Description

To make Solution A:

Dissolve 38.41g of Potassium Bromate acid in 400-600ml of water

Stir then add water in a volumetric flask to make 1L

To make solution B:

Dissolve 32.26g of Malonic acid in 400-600mL of water

Add 7.021g of potassium bromide

Add water to make 1L of solution in a volumetric flask.

To make solution C: 

Dissolve 10.412g of ammonium cerium (IV) nitrate in 400mL of water. Stir

Add 150mL of concentrated sulphuric acid slowly as solution will heat up

Stir and allow to cool to room temperature.

Add water in a volumetric flask to make 1L of solution.

Solutions will store in sealed containers for a few weeks without degradation.

Solution D is off the shelf:

Clock Procedure 

In a 1 Litre Flask add 300mL of solution A to 300ml of solution B.

Wait until solution clears.

Add 300mL of solution C.

Wait till solution fades to yellow Cerium colour

Add 3.6mL of solution D.

The chemical clock reaction should commence with the solution cycling through green purple red blue and back with about an initial 60 second total cycle time.

Concentric circles

Add 2.5mL of Solution A and 2.5mL of solution B to a Petri dish

Add 2.5mL of solution C to the dish

Add 1mL of solution D

Mix well

Concentric rings should develop after 1 minute.

Note: 

Chemicals A, B and C can be prepared and stored for up to a year in sealed containers.

Videos

Chemical Clock Images

  • Chemical Clock

    Chemical Clock 1Chemical Clock 2Chemical Clock 3Chemical Clock 4Chemical Clock 5Chemical Clock 6 Chemical Clock 7Chemical Clock 8Chemical Clock 9Chemical Clock 10Chemical Clock 11Chemical Clock 12Chemical Clock 13Chemical Clock 14

  • Concentric Rings

    Chemical Clock Rings 1Chemical Clock Rings 2Chemical Clock Rings 3Chemical Clock Rings 4Chemical Clock Rings 5Chemical Clock Rings 6Chemical Clock Rings 7Chemical Clock Rings 8

Safety Notes

Chemical Clock SOP-11