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An investigation to find out how the concentration of acid affects the rate of the reaction between HCl and CaCO3

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Introduction

An investigation to find out how the concentration of acid affects the rate of the reaction between HCl and CaCO3 Skill Area P: Planning Experimental Procedures Introduction and Preliminary Work I am attempting to find out what affect the concentration of hydrochloric acid has on the rate of the reaction between HCl and marble chips (calcium carbonate). The equation of this reaction is as follows: CaCO3 (s) + 2HCl (aq) --> CO2 (g) + CaCl2 (aq) + H2O (l) calcium + hydrochloric--> carbon + calcium + water carbonate acid dioxide chloride There are many factors which can affect the rate of a reaction. The temperature of the acid will have an impact on how quickly a reaction occurs. I carried out a preliminary experiment on the affect of temperature as the variable, by using water baths and thermometers to obtain four different water temperatures in which the flask containing acid and marble chips was placed. I used four different water temperatures from 20�C to 50�C, going up in 10�C each time. I carried out two tests for each temperature, and noted the change in mass every minute for ten minutes as the chips dissolved, and I took an average of the two sets of results. I found that, the higher the temperature of the water bath, the faster the reaction happened. This was because, as the kinetic theory explains, a high temperature gives the particles of the reactants more energy to move (and react) faster. I am not choosing to use this factor in my current investigation because it was quite difficult to obtain accurate results, as the water baths didn't always maintain the correct temperature. This caused a few errors in my results. I also did a preliminary experiment in the same way on the effect of the size of the calcium carbonate chips on the rate of the reaction. This was an experiment that proved that the larger the surface area of the chips (i.e. ...read more.

Middle

This is because there are fewer particles in a less concentrated solution to collide with each other, so the reaction will be slower. The rate of a chemical reaction is increased as the concentration of the reactants also increase. This will be happening while the acid and the marble chips react, and is known as the collision theory. As I am using five concentrations of acid, I am going to try to prove that the rate of reaction will be doubled as the concentration doubles. That is, I predict that the reaction will be twice as fast when I am using 2M acid than when I'm using 1M acid, and also twice as fast using 1M as using 0.5M. Equipment list Conical flask - to house the reaction between the acid and the chips. Electronic top-pan balance - to ensure that I am able to record accurate readings of the mass in grams, to two decimal places. 100cm� Measuring cylinder - to measure accurately the correct volume of hydrochloric acid that I will use. Timer - to time one-minute intervals over a period of ten minutes accurately. Reactants 0.1M, 0.5M, 1M, 1.5M and 2M hydrochloric acid - for varying concentrations. This is so I can obtain a good range of results, so I can prove or disprove my prediction, and so come to a definite conclusion. I will require 40cm� of each concentration in order to carry out two tests for each. 100g medium sized marble chips - 10g for each of the five experiments and 10g for each of the second tests. Skill Area O: Obtaining Evidence Tables of Results 0.1M concentration: Time (minutes) Mass (grams) including flask 1st Test 2nd Test Average 0 1 2 3 4 5 6 7 8 9 10 83.71 83.70 83.69 83.65 83.64 83.68 83.68 83.67 83.67 83.66 83.66 83.89 83.87 83.87 83.86 83.85 83.84 83.84 83.83 83.83 83.83 83.83 83.80 83.79 83.78 83.76 83.75 83.76 83.76 83.75 83.75 83.75 83.75 Total decrease in mass: 0.05g 0.06g 0.055g 0.5M concentration: Time (minutes) ...read more.

Conclusion

This would make the investigation better by giving me much more accurate results than a top-pan balance did. I would change my method slightly, again to obtain more accurate results, by measuring out the volume of hydrochloric acid more carefully when using a 100cm� measuring cylinder, with the 20cm� mark level with my eyes. These changes would also make my results more reliable because they would be more accurate. My investigation was a fair test, apart from the acid and marble chips not being measured out completely accurately. I have mentioned that I used small chips instead of medium but, as I used them for every variable of the concentration of acid, the experiment remained a fair test. The only real difficulty I met was not getting started soon enough to find that I had to wait in order to get the correct equipment, for example, a top-pan balance and all five acid concentrations, to begin obtaining my results. This was also why I had to use small marble chips. Obtaining Further Information To get more information on this topic before carrying out an investigation, I could have looked at a few more books and websites to be sure of the scientific ideas behind the experiment. If I had more time at the end of this experiment, I could have carried out another one, using a gas syringe in order to obtain an extra set of (hopefully) better and more accurate results. This would make me surer of the conclusions I have drawn because I would have more evidence to back up what I was saying. This method would give me new information and not just more of the same because different, more accurate equipment would be used. Also, a gas syringe would enable me to measure the amount of gas given off by the reaction, so the results would also be of a much different nature to the ones I have already obtained. ?? ?? ?? ?? Sarah Aldridge 11u3 ...read more.

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