Context

Chemical Kinetics is one of the branches of chemistry that studies the speed of chemical reactions, as well as the factors that can influence them. It is extremely relevant to a variety of fields, such as pharmacy, medicinal chemistry, biochemistry, chemical engineering, and environmental chemistry.

The reaction order, specifically, is an extremely important component within Chemical Kinetics. It is what allows us to determine the relationship between the speed of a reaction and the concentration of its reactants. This is vital in industry, for example, where it is necessary to know at what rate a reaction will occur, so that the production process can be effectively planned and managed.

Introduction

The study of 'Reaction Orders,' in the context of Chemical Kinetics, refers to how the speed of a chemical reaction changes when we alter the concentration of the reactants. The 'Reaction Order' is generally expressed as an exponent in the reaction speed equation. These exponents can be 0 (reactant does not affect the reaction speed), 1 (reactant directly affects the reaction speed), or 2 (changes in the reactant have a quadratic impact on the reaction speed), etc.

But the study of the subject is not limited to these cases only; we can find cases where the reaction order is a fraction, a negative number, or even a variable number. Therefore, the study of reaction orders is a field full of interesting and varied possibilities.

The order of a reaction is determined experimentally and cannot be predicted from the chemical reaction equation. This means that, to calculate the reaction order, we need to conduct experiments, collect data, and analyze this data using chemical kinetics tools.

Practical Activity

Activity Title: Dissecting Kinetics: Experiment to Determine the Reaction Order

Project Objective

The main objective of this activity is to provide students with a real experimental practice to understand the determination of the reaction order. Through the experiment, they will learn how to collect data, how to analyze the data, and how to determine the order of a chemical reaction. Additionally, they will develop teamwork skills and time management competencies.

Detailed Project Description

Students will work in groups of 3 to 5 people and will have one week to complete the project. The practical activity should take two to four hours to be carried out by each group member.

The activity consists of conducting a simple chemical reaction experiment, measuring the variation of the reactant concentration over time, collecting this data, and finally determining the reaction order.

Required Materials

1. Stopwatch
2. Hydrogen peroxide (H2O2) solution at a known concentration
3. Potassium iodide (KI) solution
4. Test tube racks
5. Test tubes
6. Pipettes
7. Analytical balance
8. Distilled water for dilutions
9. Starch indicator paper

Activity Steps

1. Form the groups and distribute the materials.

2. Explain the experiment procedure: The reaction we are going to study is the reaction between hydrogen peroxide and potassium iodide, which produces water and iodine: 2H2O2 + 2KI → 2H2O + 2KOH + I2

3. Each group should perform the reaction at different concentrations of hydrogen peroxide. They should dilute the hydrogen peroxide solution with distilled water, noting the final concentrations.

4. After mixing the hydrogen peroxide solution with the potassium iodide solution in the test tubes, start the stopwatch.

5. When the solution starts to turn blue (indicating the formation of a small amount of iodine), stop the stopwatch and note the time it took for this to occur.

6. Students should repeat the experiment for each concentration of hydrogen peroxide and collect all time data.

7. Based on the collected data, students should plot graphs and determine the reaction order with respect to hydrogen peroxide.

8. Finally, students should conclude the activity by writing a report on the experiment, including Introduction, Development, Conclusions, and Bibliography.

Project Submission

Students must submit a written report on the project. The report should include:

1. Introduction: The student must contextualize the topic, its relevance and real-world application, as well as the objective of this project.
2. Development: Detailed description of the experiment conducted, explaining the theory behind the reaction order and the methodology used. Students should present the collected data and the generated graphs. In this section, they should also discuss the results, explaining how they reached their conclusions.
3. Conclusion: Return to the main points, explaining the learnings obtained and the conclusions drawn from the project.
4. Bibliography: Declare the sources from which information was gathered to work on the project, including books, videos, web pages, among others.

Thus, by the end of the project, they will have experienced a real situation applying the concepts of chemical kinetics. Additionally, they will have worked on important skills such as teamwork, time management, communication, and problem-solving.