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Rates of Reaction

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Introduction

Reaction Rate: Reaction rate is simply the rate (usually measured in units/time) that two or more reactants take to complete a chemical reaction. A Brief Introduction to Rates of Reaction Reaction rate can be measured in many different, but effective and accurate ways. Some of these can include measuring: change in heat over time (?H/t), amount of gas produced over time over time (?V/t), the change in concentration over time (?Ph/t) and even change in colour over time (?colour/t). Another way of measuring reaction rate is by timing how long it takes for a reactant to be consumed (disappear), or by timing how long it takes for a new substance to be created (appear). A formula has been derived that is able to calculate the rate of a chemical reaction. This is called the "Rate Equation". The diagram to the right shows the different components that form the rate equation. There are 3 main ideas/aspects that can be noticed in the given reaction equation. The values in the brackets refer to the concentrations of the different reactants. Only the values in the brackets are related to concentration. The rate constant (k) is not really a constant at all. It varies when aspects of the reaction are changed such as the temperature, changing of catalysts or varying surface area, as these factors prevent different reactions from correctly being able to be compared. Therefore, the constant only applies when the only variable in the equation is the concentration. The powers that apply to the concentration values are the orders of reactions. These figures can only be positive, can be represented by a fraction eg. Decimal value, and determine the overall order of reaction for the equation. ...read more.

Middle

This involved sticking a burning splint over the end of a test tube with the reaction taking place. If a popping sound is heard, it means that the gas being produced is hydrogen. To measure the reaction rate in this experiment, a tub of water was set up and a measuring cylinder was filled to the top with water, and turned upside-down and placed into the tub of water, so that the volume of gas produced in the reaction could be measured in the cylinder. The reactants were placed into a sealed bottle that had only one exit, a tube that extended out the top. This tube was hooked under the cylinder so that the gas would run through the tube and go into the cylinder to be measured. Three different concentrations were made which included: Volume of 3M Sulphuric Acid Volume of Distilled Water Concentration Produced 30mL 0mL 3M 20mL 10mL 2M 10mL 20mL 1M This reaction was slow, so the reaction rate was recorded by measuring the amount of gas produced per minute, rather than the time taken for the reaction to complete, as that could have taken hours or even days. Another experiment was performed using the same reactants, but the surface area of the zinc was varied instead. Both zinc powder and zinc chips were used in the reaction. Once again, the volume of gas per minute was recorded. The 3M concentration of acid was used, as it would produce better, faster results than any other. Prediction - Once again, the higher the concentration of SO4, the quicker the time of reaction will be, and the higher the rate of reaction. The higher the surface area, the slower the time will be and the lower the rate of reaction will be. ...read more.

Conclusion

This means that the reaction rate is directly proportional to the concentration of the iodide, and the time for reaction to complete is inversly proportional to the concentration of the iodide. Experiment 4. - If the hydorgen peroxide had been as available to us as anyone else, three catalyst experiments would have been performed. One involving liver (blood), one involving Mangenise Dioxide (MnO2) and one with Iron Sulfate (FeSO4). Without actually performing the experiments, it is impossible to begin to predict how the time of reaction would have been effected by the different catalysts. However, upon examination of other people's experiments, it became evident that all of the catalysts used in each of the experiments sped up the reaction greatly, some to the point where it became impossible to even measure the volume of gas produced. Conclusion Overall, I feel that, apart from the hydrogen peroxide prac, the entire investigation was a success. Valid information was acquired and was successfully integrated into the analysis of the experiments. The subject of reaction rate was researched and experimented on as well as related topics such as the reaction equation, order of reaction, collision theory and activation energy. If I were to do this experiment again, these are just some of the things I would change: - Make sure I use the right equipment - Make sure the equipment is clean - Do the experiments multiple times in order to gain more results so that there is less chance of using incorrect information - Manage my time more wisely so that I could have time to analyse each experiment and detect faults and perhaps retry experiments - Investigate every possible way of changing the experiment(s) to involve all factors contributing to reaction rate ...read more.

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