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How does concentration affect the rate of a chemical reaction?

Extracts from this document...

Introduction

How does concentration affect the rate of a chemical reaction? By Tom Pattle Contents Planning - Pg 2-7 Introduction - Pg 2 Background Knowledge - Pg 2-7 References - Pg 7 Prediction - Pg 8-10 Method - Pg 9 Apparatus - Pg 9-10 Fair test - Pg 10 Analysing evidence -Pg 11-12 Line graphs Conclusion - Pg 13 Evaluation - Pg 14-15 Plan Introduction The experiment is about the concentration of sodium thiosulphate affecting the rate of a chemical reaction when using hydrochloric acid. Here is the word equation for the chemicals that will be used: Sodium thiosulphate + hydrochloric sodium + water + sulphur + sulphur acid chloride dioxide Also, the symbol equation: Na2S2O3(aq) + 2HCl(aq) 2NaCl(aq) + H20(l) + SO2(g) + S(s) When this reaction takes place, a precipitate of insoluble sulphur will form. The time it takes for a cross to be blocked from view will be measured showing the cloudiness of the precipitate and the rate of reaction. Background knowledge For the reaction in this practical to take place, a thiosulphate (S2O32-) ion has to collide with a hydrogen ion (H+). Here is the symbol equation for this chemical reaction that will happen during the experiment: S2O32-(aq) + H+(aq) H2O(u) + SO2(g) + S(g) But for the reaction to happen, the S2O32- ions and the H+ ions have to collide at the right angle and with enough speed to overcome the activation ...read more.

Middle

In scientific terms, the speed of the reaction is inversely proportional to the time taken for the reaction to finish, Speed of reaction = 1/Time You can see this from the diagram below, 1/Time = Concentration: Method For the experiment to be carried out the equipment will have to be set out as below: * Draw a cross (using a HB pencil) onto a piece of paper, * Measure out 5cm2 of Sodium thiosulphate from a burette and then pore into conical flask, * Measure out 45cm2 of distilled water and place it into the conical flask, * Next swirl once to the mix solution, * Place the conical flask on the crossed paper and take the temperature, * Then add 10 cm2 of hydrochloric acid, * Again swirl the solution and start the stop clock, * Now time how long it takes for the cross to be blocked from view. After that is completed the experiment will be repeated before going onto the next concentration. Goggles must be worn to stop liquid splashing into person's eyes. Apparatus The equipment that will be used for the practical is below in the form of a list: * Conical flask * Stop clock * Burette * Measuring cylinders * Piece of paper with a drawn cross in the middle of it * HB pencil * Ruler * Thermometer Fair test To make sure that the practical is a fair ...read more.

Conclusion

So if the experiment were to be repeated the above details would be improved by: * A computer clock program could be used to take the time to make the results more accurate by using a light and a LDR sensor to record when the cross is obscured from view, * The apparatus could be washed out using distilled and water, * A burette could be used for all of the solutions to make the measurements more accurate, * A magnetic stirrer would keep the solution swirling at a constant speed, * A heating mantle may be used to keep the temperature of the solution the same. These more precise pieces of equipment would overcome a persons subjective judgement and to give consistent conditions. Repeating the results for a 4th time could help to improve the reliability and also eliminate anomalous results. There are some other experiments and techniques that could be used to improve of extend the coursework: 1. To make your prediction more accurate the results could be taken over a wider range by increasing the concentration by smaller variations e.g. every 2cm2, 2. A different experiment could be carried out to extend the work where a different acid would be used e.g. HNO3 - nitric acid, 3. Also, to extend the coursework, instead of changing the concentration of the sodium thiosulphate the acids concentration would be changed. ?? ?? ?? ?? 0 ...read more.

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