Briggs-Rauscher

Materias needed:

Potassium iodate
Sulfamic acid
Malonic acid
Manganese(II) sulfate
Starch powder
Hydrogen peroxide
Distillied water
Beaker
Cylinder
Weighing scale
Measuring cylinder

Written by: Gahyeon Park (Procedure + Results) & Sophia Han (Evaluation)

Step 1

Create solution A by adding 100ml of distilled water, 1.5g of malonic acid, 0.4g of manganese (II) sulfate and 0.1g of starch.

Step 2

Create solution B by adding 90ml of distilled water, 10ml of sulfuric acid and 4.3g of potassium iodate.

Step 3

Create solution C by adding 100ml of 10% hydrogen peroxide.

Step 4

Add solution A and B in order and start the magnetic stirrer. As soon as it gets mixed add solution C. (Our school didn't have a magnetic stirrer so we mixed it using a glass rod.)

Result

Originally, the solution has to show 2 main colors. Yellow and blue. However, our solution only showed a color change from yellow to orange and after sometime the solution turned brick-red with gas bubbles on top.

How did this happen?

Iodic acid and hydrogen peroxide reacts and makes iodine where the color of the solution changes from transparent to yellow. Now, the iodine and the malonic acid reacts and makes iodine ion. As iodine and iodine ion react, the color changes from yellow to blue.

Color change equation:

I− + I2 + I-3 + Starch

(Transparent) (Yellow color) (Blue color)

Overall reaction:

IO3 + CH2(COOH)2 + 2H2O2 -> ICH(COOH)2 + 2O2 + 3H2O

Iodate ion + Malonic acid + Hydrogen peroxide -> Iodomalonic acid + Oxygen gas + Water

Evaluation

Written by: Sophia Han

The results we obtained differed significantly from the expected results of the experiment (an oscillatory cycle that turns from colorless to amber to blue).

The most plausible key reason we found for the failure at our attempt at creating the Briggs-Rauscher reaction was due to the incorrect concentration of reactants. Because the reaction requires precise measurement of the solutions, even small variations can cause the reaction to produce unexpected results. During the experimental procedure, we did not dilute the sulfuric acid and hydrogen peroxide properly, causing them to be present in a state in which their concentration is too high. This may lead to high exothermic reactions, which break down other compounds and bring out black bubbles and a burnt smell.

It is important to ensure that the apparatus and chemicals used are clean and do not contain any impurities or contaminations as well for the reaction to take place properly without errors and to increase the reliability of the experiment.

Fun fact!

The Briggs-Rauscher reaction is a type of an oscillation reaction, as it can be observed by the repeated color change. Oscillatory reactions are essentially reactions in which concentration of reactants and products periodically reverses themselves.