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Rates of Reaction.

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Introduction

Chemistry Coursework Rates of Reaction Introduction This experiment was to determine the effect of changing one of the substrates when hydrochloric acid was mixed with calcium carbonate powder (chalk). For this experiment, the variable was the concentration of the acid. This was chosen in preference to calcium carbonate because it is difficult to determine particle size and subsequently measure an exact reaction, as smaller particles react quicker than larger particles. The different concentrations of the hydrochloric acid were made up according to the following table:- 100cm3 2m acid + no water = 2m 90cm3 2m acid + 10cm3 water = 1.8m 80cm3 2m acid + 20cm3 water = 1.6m 70cm3 2m acid + 30cm3 water = 1.4m 60cm3 2m acid + 40cm3 water = 1.2m m = moles 50cm3 2m acid + 50cm3 water = 1m 40cm3 2m acid + 60cm3 water = 0.8m 30cm3 2m acid + 70cm3 water = 0.6m 20cm3 2m acid + 80cm3 water = 0.4m 10cm3 2m acid + 90cm3 water = 0.2m The concentrations I chose were 2, 1.75, 1.5, 1 and 0.5moles. Equation The equation for this reaction is: - Hydrochloric acid Calcium Chloride + water + + Calcium carbonate Carbon Dioxide 2HCl (aq) ...read more.

Middle

These are: * Giving the atoms more energy. This will make the molecules move faster and therefore collide more often - this is achieved by raising the temperature. * Varying the concentration. A concentrated solution contains more molecules per cm3 than a dilute solution; therefore the molecules collide more often. * Changing the surface are. A larger surface area, smaller particles/powder exposes more molecules than a large chunk does; this means more collisions which then leads to a faster reaction time. * Introducing a catalyst. The use of a catalyst will lower the activation energy without being used up itself, once again speeding up the rate of the reaction. Results Table Gas produced within 2 minutes ml3 Acid concentration moles 1 2 3 4 5 Average 0.5 20 16 16 15 10 14.2 1 45 61 47 56 63 54.4 1.5 100 105 115 105 128 110.6 1.75 75 130 140 130 135 122 2 160 205 172 166 179 176.4 Graph Graph to show the volume of gas produced in 2 minutes when hydrochloric acid is mixed with calcium carbonate Acids, Bases and Alkalis To explain this experiment, we need to understand how acids and alkalis react together. ...read more.

Conclusion

I recalculated the average ignoring this result and it brought the average up to 134. When the graph was then re-plotted, it showed a straighter line. See below. This leads me to believe that the line above should be straight, showing a steady increase in gas volume with acid concentration. One way the accuracy could be improved is to measure the calcium carbonate powder straight into the conical flask on the scales, rather than doing it on filter paper, which would then prevent the loss of some of the powder. Another way to improve the accuracy of the concentrations of the hydrochloric acid would be to measure it in a burette rather than measure it out in beakers, as these tend to be better calibrated. I am positive that my experiment is accurate enough for my conclusion to be correct. If I were to do my experiment again I would keep the method the same, but would introduce the above amendments. It would be interesting to see how other variables would change the rate of the reaction, for example, the temperature could be varied, and the particle size of the calcium carbonate could be varied. I would also like to try this experiment with other alkalis such as calcium or sodium hydroxide to see if they react the same as the carbonate. Ross Bowman 1 ...read more.

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