Chemistry IA: Kinetic Reaction With H2O2

Chemistry IA – Kinetic Experiments

Practice Internal Assessment

Investigating the relationship between KI concentration and its rate of reaction with H2O2, which is measured using a spectrophotometer.

Research Question

How will changing the concentration of KI affect its rate of reaction with hydrogen peroxide? Calculated as inverse of time taken for the blue-black coloration of tri-iodide ion and starch solution, measured using a spectrophotometer.

Introduction:

The rate of reaction of a chemical reaction can be affected by several factors, one which is the concentration of the reactant(s). According to the collision theory, it tells us that as the concentration of the reactant increases, there will be an increase in the amount of molecules,

0.1M 0.05M 0.025M 0.0125M 0.00625M

Use equation C1V1 = C2V2 to calculate the amount of water needed to dilute the solution.

10ml of 0.1M KI + 10ml of deionized water = 20ml of 0.05M KI

Measuring the time for the colour change to occur

Using a pipette, add 1ml of H2O2, HCl, starch solution and 3ml of S2O3 into a cuvette. Set up the spectrophotometer and put the cuvette into the machine Data collection starts now, allow 5 seconds. Using a pipette, now add 1ml of KI into the cuvette containing the mixture. Data for this is collected for 300 seconds Repeat the steps above (1-5) three times to collect the average for the specific concentration. Repeat the steps above (1-6) using different Ki concentrations the collect the average for all the different concentrations of KI used in the experiment.

Data Collection and Processing

Qualitative Data Before any concentration of KI is added, the mixed solution is

However, If a mistake was made by adding too much water or too much KI, the error would be carried on and therefore will have influenced the overall results greatly. There are not a lot of improvements to this, but one way is to dilute the concentrations 1 by 1 instead of going through a serial dilution although it takes a vast amount of time.

The 5 second wait before adding KI: Since there was a 5 second wait before adding the KI into the mixture of different solutions, and also that this was added manually, the prediction of 5 seconds may have varied and therefore could have minor effects on the absorbance change. Instead of allowing 5 seconds to pass before adding the solution of KI into the mixture, all of them could be added at once and data collection can start