Briggs-Rauscher Reaction

Briggs-Rauscher Reaction

JJ, Anneliese, Gary, & Jordan

History

Rate Law

Materials List

Time vs Concentration

• 30% H2O2
• Soluble starch
• KIO3
• Deionized water
• 1 M H2SO4
• Large beaker
• MnSO4•H2O
• Graduated cylinders (3)
• Malonic acid
• Stir plate / stir bar

• Also known as the Oscillating Chemical Reaction (chemical clock)
• The Briggs-Rauscher (BR) reaction was first reported in 1973. The reaction is a variant of the Bray reaction, first reported in 1921.
• The Bray reaction uses hydrogen peroxide (H2O2) as an oxidant and reductant when mixed with potassium iodate and sulfuric acid, to create an oscillation that produces oxygen gas.

Integrated Rate Law - the relationship between concentration of reactants or products and time.

K tells us whether a reaction is fast or slow.

The larger value, the faster the reaction.

In an oscillating reaction, each concentration depends on one another. This is also known as a system of coupled differential equations.

Rate=K[IO3][H]

Procedure

Reaction Hypothesis

What is an Oscillating Reaction?

1. Solution A: Prepare 100 mL of 9% H2O2 by diluting 30 mL of 30% H2O2

with 70 mL of deionized H2O.

2. Solution B: Prepare an acidified 0.2 M KIO3 solution by adding 10 mL of

1.0 M H2SO4 to 80 mL of deionized water. Dissolve 4.3 g KIO3 in this

solution and dilute to 100 mL.

3. Solution C: Prepare starch solution by dissolving 0.1 g of soluble starch in

90 mL of boiling deionized water. When cool, add 1.5 g malonic acid, 0.4

g MnSO4•H2O, stir and dilute to 100 mL.

4. Add 50 mL of Solution A to a clean beaker fitted with a stir bar. Next add

50 mL of Solution B and let solutions mix thoroughly. Once complete, add

50 mL of Solution C and let reaction stir. Upon addition of the final

solution, bubbles should appear. The solution will turn yellow then blue,

then colorless. This reaction will oscillate for 5-10 minutes.

When the reactants are mixed, an oscillating reaction will occur, changing the colour of the solution from clear, to yellow, to blue, to clear, repeating itself.

It is a chemical reaction where during an amount of time, the concentration of a chemical species is very low, but rapidly increases at the end of this period of time. This extreme change in concentrating causes interesting effects on the reaction. (color change)

Purpose

To show the changes of concentration of the ions and molecules in an oscillating reaction

Explanation: Graph represents experiment, demonstrating

the Briggs-Rauscher Reaction

Reaction

Two Processes for Reaction (1):

a radical process caused by lower concentrations of iodide

Both processes reduce iodate to hypoiodus acid

radical reaction produces them faster

Translated into English

• For the first reaction, it can occur by two process, radical and nonradical which is determined by the concentration of iodide ions in the solution. When [I-] is low, the radical process will dominate. When [I-] is high, the nonradical process will be the dominant one.
• The reaction consumes HIO more slowly than that species is produced by the radical process when that process is dominant, but it consumes HIO more rapidly than it is produced by the nonradical process.