Kinetics of the persulfate iodide clock reaction. 1 2023-01-07

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The persulfate-iodide clock reaction is a classic chemical kinetics experiment that demonstrates the concept of a rate-determining step and the effect of various factors on the rate of a chemical reaction. In this reaction, a solution of potassium persulfate (K2S2O8) and sodium iodide (NaI) is mixed together and the time it takes for the solution to change color is measured. The reaction can be written as follows:

2K2S2O8 + 2NaI -> 2K2SO4 + I2 + 2Na2SO4

The key feature of this reaction is that it proceeds through a series of intermediate steps, rather than occurring all at once. The first step is the slowest, or rate-determining step, and controls the overall rate of the reaction. This step involves the formation of intermediate species known as iodide ions (I-) and persulfate ions (S2O8^2-).

The rate of the persulfate-iodide clock reaction is affected by a number of factors, including the concentration of the reactants, the temperature, and the presence of catalysts. Increasing the concentration of the reactants will generally increase the rate of the reaction, since there are more reactant molecules present to collide and react. Similarly, increasing the temperature will also increase the rate of the reaction, as the increased kinetic energy of the reactant molecules will make it more likely that they will successfully collide and react.

Catalysts can also affect the rate of the persulfate-iodide clock reaction. A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. In the persulfate-iodide clock reaction, a variety of substances can act as catalysts, including certain metals and organic compounds. These catalysts work by providing an alternative pathway for the reaction to proceed through, which can be faster than the uncatalyzed reaction.

In summary, the persulfate-iodide clock reaction is a useful tool for demonstrating the concept of a rate-determining step and the effect of various factors on the rate of a chemical reaction. By carefully controlling the conditions of the reaction, it is possible to gain a better understanding of the underlying kinetics and mechanisms involved in the reaction.

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kinetics of the persulfate iodide clock reaction

The charges of ions are also related to its ionic strength. In this experiment two colorless solutions are put together, at first there will be no visible reaction. Figure 3 The components of the solution. At this point any further iodine, I 2 , produced will react with the starch to form a blue black complex and the timing of the noticeable colour change provides an indication of the initial rate of the reaction. During this circumstance the temperature does not affect the rate constant of the reaction. Delas Llagas Date Performed: March 11, 2014 3ChE-A Group No.

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Experiment 4: Kinetics Of The Persulfate

kinetics of the persulfate iodide clock reaction

The heating was continued until the mixture was homogenous. Strategies used to follow the rate of reaction depends on the type of the reaction to be followed for example, if one of the reactants or products absorbs light strongly and distinctly from the other reactants and products such type of reaction can be followed by using spectrophotometric technique. Oliveira and Roberto B. In this experiment, the rate of consumption of the iodine will be measured to determine the rate of the reaction. If no changes are observed. The starch solution was added to a vigorously boiling 50 mL of distilled water. Also it is recommended to make sure that the apparatus that you will be using are clean.

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COSHH_CH1PRA_Kinetics of the persulfate

kinetics of the persulfate iodide clock reaction

After awhile, the solution suddenly turns to a shade dark blue. A known amount of thiosulfate ions will be added to the reaction vessel which will in turn consume iodine as it is produced. Orders can only be determined experimentally. The amount of the thiosulfate that is added to the solution indicates how much iodine was produced through the time taken by the reaction to turn blue. The amount of thiosulfate ions added tells us how much iodine had been produced in the time taken for the reaction to turn blue.

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A kinetic study of potassium iodide with potassium persulfate using iodine clock reaction

kinetics of the persulfate iodide clock reaction

The iodine produced is immediately consumed by the added thiosulfate ions. Unlike the stoichiometric coefficients determined by calculation, the orders of the reaction are based on the kinetics of the reaction. Laboratory coat and eye protection are mandatory at all times. When iodide reacts with persulfate ions, the reaction produces iodine and sulfate. The rate coefficient k of ionic reactions depends on the ionic strength or salinity of the solution. Treatment of Results: Determination of rate constant. If it is neutral.


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EXPERIMENT 4: KINETICS OF THE PERSULFATE

kinetics of the persulfate iodide clock reaction

Brief list of key stages of process 1. On the other hand, the experiment for the rate constant k, also shows that it is affected and have direct relationship with temperature. The prepared solutions were labeled as A. The time of the appearance of the color blue was recorded. When all the thiosulfate is consumed, free iodine starts to form in solution. The product of the charges of the ions can indicate if the rate of the reaction would increase or decrease. Conclusion and recommendations: Conclusion: The experiment successfully demonstrated the reaction between iodide and persulfate.

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MINI COSHH_CH1PRA_Kinetics of the persulfate

kinetics of the persulfate iodide clock reaction

The potential causes of the contamination are the chemical reagents may not be properly sealed in the storage, students who get their sample return the excess back to the container again, and also there are students who directly put their instruments into the container of the chemical reagents. The slopes of graph 1 and graph 2 will give you m and n, respectively round them to their nearest integer values. The flask was gently swirled and the time was recorded when the resulting solution turned to blue. Hazard Harm Control measures Electrically heated water bath Electrocution, scalding Ensure electrical equipment has been safety checked. This actually make sense because there will be greater chance for molecules to collide and speed up the reaction rate. The prepared solutions were labeled as A, B, C, and D respectively. Preparation of the following solutions: 0.


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kinetics of the persulfate iodide clock reaction

And the slope from the graph of potassium iodide is 0. None Precautions Electrically heated water bath, could cause Electrocution, scalding Glassware, Broken glassware can cause skin cuts Chemical Hazards Compound name Form s, l, g, aq? Potassium chloride KCl and potassium sulfate K2SO4 are used to maintain the ionic strength of the solutions. Starch indicator was prepared by adding 0. The computed over-all order of the reaction is far from the theoretical value which is 2. Both test tubes were put into a water bath afterwards for 10 minutes. The method is based on the measurement of the rate of the reaction over a period of time.

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kinetics of the persulfate iodide clock reaction

On the otherhand, sodium thiosulfate was used to reduce iodine back to iodide before iodine can complex with the starch to form the characteristic blue-black color. Delas Llagas Date Performed: March 11, 2014 3ChE-A Group No. The amount of the thiosulfate that is added to the solution indicates how much iodine was produced through the time taken by the reaction to turn blue. This diluted solution will be used along the experiment. If the mixture changed its color upon the addition of solutions a and b to solutions c and d , a decrease in the amount of NH4 2S2O8 solution and increase of the amount of Na2S2O3 solution by 1 mL is advised. PHI Learning Pvt Ltd.


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