Rates of Reaction Lab
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Rate of Reaction Design Experiment Effect of concentration on the rate of reaction between a metal and an acid Introduction In chemistry, chemical kinetics is the study of the factors affecting the rate of a chemical reaction. By definition, rate is the increase in the concentration of one of the products per unit time or decrease in the concentration of one of the reactants per unit time. Many factors trigger the rate of reaction, such as concentration, surface area and temperature. I will investigate the effect of concentration on the rate of reaction between a metal, zinc (Zn), and an acid, hydrochloric acid (HCl). According to the collision theory and based on my experimental results, I will prove my following hypothesis to either be correct or incorrect in theory. Design (D) Aim To investigate the effect of concentration of HCl on the rate of reaction of zinc (Zn)) by measuring the volume of hydrogen produced. Hypothesis As the concentration of the hydrochloric acid (HCl) is increased, the rate of reaction per unit time will increase up to a certain concentration too, until an increase in the concentration of the acid will no longer effect the reaction rate. According to the collision theory, the more concentrated the reactants the more collisions there will be per second per unit volume.
Since the hydrochloric acid was in excess, the zinc dust gradually disappeared as it reacted with the acid to give a colourless solution of zinc chloride mixed with remaining acid. The zinc in the flask disappeared quickest at 3M hydrochloric acid. The Reaction Zn(s) + 2 HCl --> ZnCl2(aq) + H2(g) Data Processing Gradients of all three curves in the graph attached represents the reaction rates of each. To determine the reaction rate: Reaction rate= Change in volume Change in time Examples of how the reaction rate was determined are shown on the graph attached. Uncertainty= ±0.5 Reaction rate of 1M hydrochloric acid= 2.0ml min-1 Reaction rate of 2M hydrochloric acid= 5.0ml min-1 Reaction rate of 3M hydrochloric acid= 7.5ml min-1 How the average was calculated: Value of Trial 1 + Value of Trial 2 = Average value Number of trials Example: Time (mins) (± 0.03) Volume of hydrogen gas(ml) collected at 3M hydrochloric acid Trial 1 Trial 2 Average 0.00 0.0 0.0 0.0 0.30 8.0 9.0 8.5 To calculate the average value for the 30th second of the reaction process- 8.0 + 9.0 = 8.5 2 Conclusion and Evaluation (CE) Conclusion In conclusion to the graph and the experimental results, it is safe to say that my stated hypothesis is correct.
For this method to be successful, it would be vital to ensure that the mouth of the conical flask is open. Since this reaction is an exothermic, it would give hydrogen off to the surrounding, in turns decreasing the overall mass of the final product. This method involves fewer sources of errors, and the experimental data would accordingly make more sense. Since the hard-to-move syringe piston was a reason to the inaccurate data, it would be ideal to make sure that the inside of the syringe is lubricated sufficiently so that no extra force is needed to move it outwards. Another way to minimize errors is by ensuring that the syringe, delivery tube, plastic stopper and the conical flask is completely airtight and leak-proof. This will stop the dependent variable, hydrogen, from escaping in turns giving us a more reliable and precise set of raw data. The electronic balance would also be tested prior to the experiment to ensure that it is providing accurate reading, without any doubting fluctuations. All in all, for all methods of measurement it would be best if the experiment could be carried out more than once with more than at least 6 concentrations. This would provide us with a wide enough range of values with which to plot an accurate graph to compare reaction rates and to test the hypothesis with.
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