Chapter 1.

Overview

Determining a Rate Law and Rate Constant

The learning objectives of this experiment are as follows:

• Understand the similarities and differences between zero-, first-, and second-order rate laws.
• Use absorbance measurements to track the completion of a reaction over time.
• Use data analysis and graphing techniques to determine a rate law and rate constant for a reaction.

The Department of Chemistry and Biochemistry

The Ohio State University

Intro

Chemical kinetics is the study of the speed, or rate, of reactions. We know that some reactions happen faster than others. The addition of baking soda to vinegar produces a quick reaction that we see almost instantly. Contrarily, rust forming on our cars is a very slow reaction and not something that we will notice in minutes. It is often advantageous for scientists to know the speed of reactions. Pharmaceutical researchers, for example, must know how fast a drug will work when it enters the body. In this lab you will study chemical kinetics. We will use absorbance measurements to track the progress of a reaction as a function of time and determine a rate law and rate constant for a chemical reaction.

Procedure

Treatment of Data

You should use a graphing program, e.g., Excel, for your calculations and graphs.

Construct a table of your data, like the one shown on the last page of the report sheet, for each solution 1 through 4. Data of “Time” and “A” will be collected in lab, and the other columns of “[CrEDTA⁻]_t,” “[Cr³⁺]_t,” “ln [Cr³⁺]_t” and “1/[Cr³⁺]_t” will be calculated.

If this experiment is performed in groups, recording of data is done together in the lab. ALL calculations, graphs, and other parts of the report must be completed individually.

Disposal of Chemicals

Credits