Iodine Clock Reaction Practical Report

Abstract

This experiment is a variation of the typical iodine clock reaction, incorporating Ascorbic acid. The objective is to achieve a colorless solution that turns blue/black within a specific time frame, initially 22 seconds and subsequently 32 seconds. The four components involved in this experiment are Hydrogen Peroxide, Potassium Iodide, Ascorbic acid, and Starch. The presence of vitamin C (Ascorbic acid) keeps the solution colorless, but once it is consumed, triiodide ions formed during the oxidation reaction combine with starch, resulting in a dark blue color (Vitz, 2007).

Introduction

A clock reaction experiment involves a chemical reaction that proceeds for a set duration until the reagents are exhausted, leading to an abrupt and unexpected change (UKEssays, 2018). In this experiment, a hypothesis was formulated: "The smaller the quantity of ascorbic acid, the quicker the component will be used up, and the faster the color change will occur." This hypothesis is based on the assumption that less ascorbic acid leads to quicker consumption of the component, resulting in a faster reaction with triiodide and starch molecules, ultimately causing a color change (Vitz, 2007).

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For safety, precautions were taken, such as wearing lab coats and goggles, and immediate rinsing if solutions came into contact with hands. The solutions used in this experiment were not harmful due to the low volumes required.

Materials and Methods

Materials

• 200μL and 100μL pipettes
• Blue tips for the 1000μL pipette
• Yellow tips for 200μL pipette
• 24 test tubes
• Test tube rack
• 10mL of 3% hydrogen peroxide solution
• 10mL of 1% potassium iodide solution
• 5mL of 50mM Ascorbic acid
• 5mL of starch solution
• Distilled water
• Stopwatch

Methods

Initially, a base amount of each solution was determined for a preliminary trial: 22μL of hydrogen peroxide, 100μL of Ascorbic Acid, 30μL of Potassium Iodide, and 50μL of starch solution.

Ascorbic acid was identified as the variable affecting the color change time, while the other measurements (solutions A, B, and D) remained constant. Different volumes of ascorbic acid were tested to determine the ideal quantity for achieving the 22-second color change. The experiment was conducted in groups of four.

Each solution was measured using pipettes, ensuring precise techniques to minimize errors. Pipetting was performed with care to prevent air bubbles and ensure accurate volume measurements. The experiment involved one member observing the color change and another using a stopwatch. Human error was minimized by selecting observant individuals for these tasks.

The rate of reaction can be influenced by factors such as temperature and concentration. Higher temperatures and increased concentrations generally lead to faster reaction rates (Mason, 2002).

Results

First Allocated Time (22 seconds)

Second Allocated Time (32 seconds)

Discussion

The experiment aimed to achieve color changes in 22 and 32 seconds, based on the hypothesis that decreasing the quantity of ascorbic acid would result in faster color changes. The results, although not exact, fell within an acceptable range of ±10 seconds.

Several factors could have improved the accuracy of the results. Improved organization and a systematic working station setup could have enhanced efficiency. Ensuring consistent treatment of each trial, including uniform mixing techniques, would have minimized variations in reaction rates.

Factors such as temperature and concentration can influence reaction rates. Higher temperatures generally lead to faster reactions, as does increased concentration (Mason, 2002).

Human error, including pipetting and observation mistakes, may have affected the results. However, minimizing these errors through careful selection of individuals and proper training can reduce their impact.

In conclusion, the experiment's results support the hypothesis, but minor flaws prevented exact time achievement.

References

Mason, C. (2002). The Effect of Temperature, Concentration, and a Catalyst on the Rate of the Iodine Clock Reaction. Retrieved from http://cssf.usc.edu/History/2002/Projects/J0512.pdf

UKEssays. November 2018. The Iodine Clock Reaction Practical Report. Retrieved from https://www.ukessays.com/essays/chemistry/the-iodine-clock-reaction-practical-report.php?vref=1

Vitz, E. (2007). A Student Laboratory Experiment Based on the Vitamin C Clock Reaction. Journal of Chemical Education, 84(7), 1156.