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Rate Equations and Order of Reaction
A topic from the subject of Chemical Kinetics in Chemistry.
Rate Equations and Order of Reaction
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical kinetics is the study of reaction rates, the factors that affect them, and the reaction mechanisms by which they occur.
The rate of a reaction is the rate at which the reactants are consumed or the products are formed. It can be measured in terms of the change in concentration of the reactants or products over time.
The rate equation is an equation that expresses the rate of a reaction as a function of the concentrations of the reactants. The rate equation is determined experimentally by measuring the initial concentrations of the reactants and the rate of the reaction at different times.
The order of a reaction is the sum of the exponents of the concentrations of the reactants in the rate equation. The order of a reaction can be zero, first, second, or higher.
The rate constant is the proportionality constant in the rate equation. The rate constant is a function of temperature and other factors that affect the reaction rate.
Demonstration of an Experiment on Rate Equations and Order of Reaction
Experiment: Determination of the Rate Law for the Reaction between Sodium Thiosulfate and Hydrochloric AcidMaterials:
0.1 M Sodium thiosulfate solution 0.1 M Hydrochloric acid solution
Starch solution Iodine solution
Graduated pipettes Erlenmeyer flasks
* Stopwatch
Procedure:
1. Rinse several Erlenmeyer flasks with distilled water.
2. Prepare a series of solutions by varying the concentrations of sodium thiosulfate and hydrochloric acid in the flasks as shown in the table below:
| Flask | [Na2S2O3] (M) | [HCl] (M) |
|---|---|---|
| 1 | 0.05 | 0.05 |
| 2 | 0.10 | 0.05 |
| 3 | 0.05 | 0.10 |
| 4 | 0.10 | 0.10 |
3. Add 10 mL of starch solution and 2 drops of iodine solution to each flask.
4. Start the stopwatch and record the time it takes for the blue color to disappear completely.
5. Repeat the experiment for each solution and record the data.
Data Analysis:
1. Plot the initial rate of the reaction against the initial concentrations of sodium thiosulfate and hydrochloric acid.
2. Determine the order of the reaction with respect to each reactant using the slope of the graph.
3. Write the rate law for the reaction.
Key Procedures:
The use of starch and iodine solution serves as an indicator for the completion of the reaction. The initial rate of the reaction is determined by measuring the time it takes for the blue color to disappear completely.
* The order of the reaction is determined by examining the relationship between the initial rate and the initial concentrations of the reactants.
Significance:
This experiment demonstrates the principles of chemical kinetics and provides a practical understanding of rate equations and order of reaction. The experiment can be used to illustrate the following concepts:
The concept of reaction rate and how it can be measured experimentally. The concept of order of reaction and how it affects the rate law.
* The use of graphical methods to determine the order of a reaction and the rate constant.