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GCSE Chemistry

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TO INVESTIGATE THE RATE OF THE REACTION BETWEEN DILUTE HYDROCHLORIC ACID & SODIUM THIOSULPHATE A. Introduction In order to investigate the rate of reaction between a dilute solution of hydrochloric acid and a solution of sodium thiosulphate, the variables that can affect the rate of reaction between any two reactants must, firstly, be identified. These variables are discussed below using the particle theory of matter, which is; that all matter is composed of particles and their behaviour can be predicted. The particles in this chemical reaction are the atoms and molecules of the reactants and the products of the reaction. Under normal conditions the particles are vibrating about a mean position, the level of energy processed by the particles can be increased by making them vibrate more. Collision theory says that reactions will proceed faster when the collisions are more frequent and with sufficient energy. The following variables affect rates of reaction. 1. Concentration of the reactant(s). A higher concentration will result in a faster rate of reaction and vice versa. This can be explained by the 'particle theory'; a high concentration of reactants will mean there are more particles of the reactants involved in the reaction. This, in turn, will increase the rate of reaction by creating more collisions between the particles, and so creating a higher chance of more successful collisions. 2. Pressure of the container in which the reactants are placed. ...read more.


5 readings, covering a large range must be taken to try and ensure accuracy for the experiment. The results were put into the form of a graph, as it was easier from the curve created to find a link between concentration of a reactant and the rate of reaction. (d) Prediction I predict that concentration and rate of reaction will be directly proportional. The higher the concentration of sodium thiosulphate, the faster the rate of reaction. The concentration and time taken for the reaction to occur/cross to disappear, however, will be inversely proportional because as concentration increases, time taken for the reaction to occur/cross to disappear decreases. A graph plotting concentration against time taken for the reaction to occur/cross to disappear will show a curve (y = a/x), this illustrates inverse proportionality. A graph plotting concentration against the rate of reaction will be a straight line (y=x), this shows direct proportionality. (e) Risk Assessment. Hydrochloric acid solution is corrosive and therefore any splashes on the skin or the eyes must be washed off with cold tap water immediately. It should be handled carefully. Safety requirements- goggles must be worn to protect eyes. Broken glass can cause injuries and all breakages of glass will be carefully removed by hand broom and a dustpan and the teacher informed. Hands must be washed after the experiment to cleanse skin from chemicals. 2. ...read more.


But the tap water used was the same for each set of tests so this can be ignored. 2. Carrying out the test with no sodium thiosulphate present to discount the possibility of hydrochloric acid and water reacting to form a cloudy solution. This could be a control. 3. Checking the temperature of the solutions before adding them to ensure that they were all the same to discount any changes effecting results. 4. Using a water bath, in which the conical flask containing the reactants is placed. A water bath will help to keep the temperature uniform throughout the experiment. A thermometer must also be kept in both the water bath and the solution, to ensure any temperature change can be recoded and accounted for. 5. Measuring the solutions more accurately by using a pipette instead of a measuring cylinder. 6. Taking more readings to give a better average result. Repeating the experiment with varying the concentration of the hydrochloric acid should give similar results and prove whether the procedure is reliable or not. The same procedure would be used but this time acid concentration is changed and sodium thiosulphate is kept constant. The experiment can also be repeated a very high or low concentrations of hydrochloric acid solution to prove that when one of the reactant is finished the reaction stops very quickly and when a lot of it present it carries on. This would give evidence than the particle and collision theory was correct. ?? ?? ?? ?? GCSE Chemistry - Uzma Tariq 1 ...read more.

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