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Rates of Reaction.

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Sara Rider Rates of Reaction. Introduction: During the reaction between sodium thiosulphate and hydrochloric acid I know that a solid sulphur will be formed and also that the solution of the two will turn cloudy before going completely opaque, also during this a poisonous gas is also given off called sulphur dioxide. For the reaction to take place I know that the particles of these two reactants must make successful collisions and that if during the reaction more particles collide successfully then the reaction will go faster, but if reacted alongside water then the reaction will be diluted slightly the rates of reaction will be lowered. From this first evidence I can make an primary prediction that doubling the concentration of the chemicals will double the rate of reaction. I predict this because if there is double the concentration then there will be double as many particles meaning that there will be a higher chance of successful collisions. Preliminary Experiment: * Measure out 30cm3 of sodium thiosulphate and 5cm3 of hydrochloric acid. * Pour the Sodium thiosulphate into a conical flask and place on a piece of paper on which a thick cross has been drawn. * Get the stopwatch ready and start timing as soon as the Hcl touches the sodium thiosulphate, continue to time until the cross is no longer visible. ...read more.


There are various factors affecting the rate of reaction that we need to take into consideration, these are: * Temperature - I will conduct all the tests at room temperature (hopefully on the same day) because temperature has an effect on the rate of the reaction. * Shaking or stirring - I will try to keep jogging of the solutions to a minimum so as not to alter the rate of reaction. * Catalysts speed up reactions. I predict that the greater the concentration of Sodium Thiosulphate (hydro) in the solution the faster the chemical reaction will take place. Therefore, the cross will disappear more quickly due to the cloudiness of the solution. But only up to a point after this the solution will not react within a reasonable time (i.e. under 30 min). On a graph I predict it would be a plateau. I think that the concentration of a solution effects' the rate of reaction because the rate of reaction depends on how frequently the molecules of the reacting substances collide. A more concentrated substance has more molecules for a given volume than a more dilute substance. Because there are more molecules about, the frequency of successful collisions is greater, and the reactions happen faster. Fair Test: In order for my findings to be valid the experiment must be a fair one. ...read more.


The measures of Hydrochloric acid will all be the same (5cm). The person timing the experiment will look for the disappearance of the cross, otherwise there would be a time lapse between seeing the cross disappear and telling the other person to stop the clock and then eventually stopping the clock. Analysis: From looking at my graph I can see that as the concentration is increased the rates are also increased by a considerable amount, although I followed all of the fair test rules I think my graph look slightly in-accurate as 6 results under the line of best fit. My graph suggests that if I double the concentration from 0.5 to 1.0 then the rates of reaction change from 1.4 to 2.1. I feel that this is also inaccurate because before we found that if then concentration is doubled then the rates are more then doubled. The reasons that concentration effected the rates are: - * If there are more particles then there will be more collisions between them. * That if the particles are colliding then the reaction will be more successful * Increasing the concentration will increase the rate/speed of the reaction. I had predicted earlier that if I doubled the concentration then the rates should be more than doubled. However my results prove this very and this was an unexpected thing to happen in my experiment. However I feel that some of my results are slightly or very much inaccurate and I would not like to use them to make any further predications ...read more.

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