Chemical Kinetics: The Iodine Clock

Introduction: The rate of a reaction is the speed at which a chemical reaction happens. If a reaction has a low rate, that means the molecules combine at a slower speed than a reaction with a high rate. Some reactions take hundreds, maybe even thousands, of years while others can happen in less than one second. (Chem for Kids, 2016). Reactions require collisions between reactant molecules or atoms. The formation of bonds requires atoms to come close to one another. New bonds can form only if the atoms are close enough together to share electron. Higher temperatures make the collisions between molecules more violent. The higher temperatures mean higher velocities. This means there will be less time between collisions. The frequency of collisions will increase. (Chem, 1999) H2O2 is the chemical formula for hydrogen peroxide. The decomposition of hydrogen peroxide will break down into oxygen and water.

This is then done for all trials. Then, once all five values of k are found, the average is taken by adding all five values of k and dividing by 5. The experimental k average is 0.105894M/s.

Next, place the first set of germinating peas, dry peas and beads and beads alone in vials 1,2, and 3. Place the second set of germinating peas, dry peas and beads, and glass beads in vials 4,5, and 6. Insert the stoppers in each vial with the proper pipette. Place a washer on each of the pipettes to be used as a weight.

The chemicals that should be mixed together include: 1 teaspoon of calcium chloride, ½ teaspoon of sodium bicarbonate, and 5 milliliters of tap water.

With silver nitrate, the solution formed a yellow greenish precipitate and with thymol blue changed the color from clear to green colored solution. With calcium chloride white ppt was formed and with hydrochloric acid gas was formed. The Vanish Crystal Bowl Cleaner with blue food coloring color changed from blue to green and with the thymol blue, a pink solution is formed. With Sliver nitrate changed color from blue to white.

The reaction turned dark blue. When Bromothymol Blue reacts with an acid, it turned orange, and when it reacts with a base, the end result is blue.

The k value in run 7 is 75% of that in run 5. This will be directly related to the addition of KNO3 in run 5 and H2O in run 7. These will make different ionic concentrations, resulting in the change in rate constant

add water to a strong acid, it can flash-boil and cause chemical burns. With the stock solution of

STEP 6: Don't throw excess solution. You can put shoe string here and wash with clean water after an hour.

In the Iodine Clock reaction experiment, we stall a reaction by having Iodine changed rapidly by two chemicals between it’s two forms. These two forms have slightly different properties. The first form of iodine is I⁻. This is not an indicator of starch. The second form of iodine is I₂. This type is an indicator of starch(a chemical that changes color in the presence of a starch).

Then, a fixed amount of sodium bisulfite/sulfuric acid/starch solution was added to each iodate solution, and the time needed to turn the mixed solution blue was recorded. Based on the measured time, reaction rate was calculated. It was found that the higher the concentration of iodate ions, the faster the reaction time. It was also found that the order of reaction was approximately 1. The result matched my prediction.

Table 2 shows the concentrations of S2O8-2 and I- and the time of each reaction for each run. Rate of the reaction was calculated by dividing 1M with the time it took to complete the reaction. The constant k was calculated using the rate law (4), the x and y value was determined by the graphs below. Considering most of the k’s calculated by our laboratory class, the supposed real value of k must be 10/Ms for that reaction.

The order with respect to Fe+3 and I- is also determined by graphing the slope of the log rate initial as a function of the log (Fe+3) or (I-). The activation energy is also graphed with the rate constant

For this experiment you have to have a basic understanding of Collision Theory to understand what’s going on in the experiment. Collision Theory is a model of chemical reactions in which a reaction occurs after a collision containing enough energy occurs between two reactant molecules. This model has five factors which can be affected and they are the nature of

The stoichiometric equation for the reaction between iodine and acetone is below, followed by the rate equation (where x,y,z and k are the values to be obtained):