Chemical Kinetics Lab 2

GEORGIA MILITARY COLLEGE

NATURAL SCIENCE DEPARTMENT

ONLINE CAMPUS

LABORATORY 2 - CHEMICAL KINETICS

NAME

STUDENT NUMBER

CLASS

PROFESSOR’S TITLE AND NAME

Introduction

A chemical reaction occurs when reagents collide with each other, resulting in a product. For collision to take place, the molecules in both reagents should have sufficient kinetic energy, which is defined as the energy that a particle in motion possesses. A primary determinant of kinetic energy is the velocity of the molecules in the reacting reagents – the higher the velocity the greater the energy. Velocity, also referred to as the reaction rate, is a measure of how fast a chemical reaction takes place. It may be affected by different factors, including temperature and the initial concentration of the reacting agents.

Taking the generic chemical reaction:

A + BC ?AC + B

Figure 1: Generic Single Displacement Reaction.

Average reaction rate for the reaction described in Figure 1 is as follows:

Average Reaction rate = -?[A] / ?t

Where ?[A] is the difference between the initial and final reagent concentrations, while ?t is the difference between the initial and final time taken for the reaction.

This laboratory sought to realize the following objectives:

i) To enhance understanding of reaction rates in chemical processes

ii) To improve ability to accurately calculate reaction rate from experimental data.

iii) To understand the effects of temperature and concentration on reaction rate.

The reaction rates for two reagents will be observed, recorded, and compared at different concentrations and temperatures. The general hypothesis is that increasing temperature and reagent concentrations will increase the reaction rate of a chemical process by increasing the kinetic energy of the individual molecules in the reactants.

Materials and Methods

Preparing the Lab

1. Click on the ‘Reactions and Rates’ Link on the Course home page to load the simulation for lab 2.

2. Accept the prompt to download the Java file to be used in the simulation on the computer’s desktop.

3. Once the simulation environment launches, select the tab labeled ‘Rate Experiments’, choose the appropriate chemical reaction, and input the initial concentrations of the two reagents (10 for reagent A) and (20 for reagent AB).

4. Check the ‘Show Stopwatch’ box at the bottom right area of the screen and select the AB molecule option. At this point, preparations for the lab are complete and all required materials are available.

Performing the Experiment

1. Click ‘Begin Experiment’ to initiate the lab and immediately start the stopwatch.

2. Monitor changes in the ‘Current Amounts’ section for both reagent A and AB. This is the indicator of concentration. Stop the stopwatch immediately the Current Amount values for both A and AB appear in the Current Amounts section.

3. Tabulate the time taken for the reaction in table 1 in the row containing the respective concentrations for both reagents.

4. Run the experiment again to be sure of the results.

5. Change the initial Concentration to 15 for A and 20 for AB, and repeat steps 1 to 3.

6. Finally adjust the initial concentrations to 20 for A and 20 for B and repeat steps 1 to 3.

7. To test the effect of temperature change, move the temperature indicator to the right slowly, while monitoring the ‘Total Average Energy’ line to ensure it marginally moves upwards, indicating a change in temperature.

8. Use this temperature to run hot setting trials using the three different concentrations for A and AB as in steps 1 to 2 above.

9. Record the time taken in each hot setting trial in the corresponding row in table 2.

Data Analysis

1. Calculate the average reaction rate using the formula: Reaction rate = -?[A] / ?t for the cold setting using the information in table 1. At this point, obtain the average rate for all three individual trials

2. Similarly, calculate the average reaction rate in the hot setting and tabulate the results in the respective row in table 2.

Data and Discussion

Results

Table 1. Initial Concentrations of reagents and average reaction rate at constant temperature. COLD Settings

Determination

[A]

[BC]

?t

Average Rate

Table 2. Initial Concentrations of reagents and average reaction rate at constant temperature. HOT Settings

Determination

[A]

[BC]

?t

Average Rate

Figure 2. Concentrations of Reagents and Average Reaction Rate in Cold and Hot Settings

Discussion

Table 1 shows the average rate of reaction at different concentrations of reagent A in cold settings. The results show that increasing the concentration of the reagent reduces the time taken for the chemical reaction, leading to an increase in the average reaction rate. This supports the hypothesis identified at the start of the experiment that increasing concentration increases the rate of chemical reaction. Increasing the concentrations of reagents means that there are more reagent particles in the chemical reaction, which leads to more collisions and consequently a higher reaction rate. The results in table 2 also indicate that the average reaction rate increases with increases in the concentration of reagent A when the experiment is carried out in hot settings.

Figure 2 compares the average reaction rate at increasing concentrations of reagent A in cold and hot settings to determine the effect of temperature on the average reaction rate. The results show that while the average reaction rate increases with increasing concentrations in both cold and hot settings, the average reaction rate is significantly higher in the hot setting. At the same time, the average rate of reaction in the hot setting increases faster than in the cold setting with a unit increase in reagent concentration. For instance, the average reaction rate increases by 0.6151 m/s (from 0.7149 to 1.33) in the hot setting when the concentration increases from 15 to 20, while it only increases by 0.025m/s (from 0.02136 to 0.04672) with a similar increase in concentration in the cold setting. This implies that, in line with the hypothesis identified at the start of the lab, temperature increases both the average rate of reaction and the increase per unit change of reagent concentration.

Temperature increases the kinetic energy of the particles in the reagents, leading them to move faster and collide with greater energy, which increases the average rate of the chemical reaction. However, since the experiment involves time measurements using a stopwatch, one could increase the accuracy of the procedure by repeating the procedure multiple times to see whether the data collected remains the same. The procedure may also be improved by synchronizing all the clocks used in the experiment to ensure they go on and off at the same time to minimize the risk of errors (Wypich, 2024).