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# The Effect of Concentration on the Rate of Decomposition of Calcium Carbonate.

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Introduction

The Effect of Concentration on the Rate of Decomposition of Calcium Carbonate. PLAN I planned my experiment based on the scientific knowledge I already have: If I increase the concentration the rate of reaction increases. This is because the higher the concentration, the more liquid (acid) particles there are in the same volume, to collide and react with the solid (calcium carbonate) particles. Therefore the rate of reaction increases. Basically the probability of the particles colliding and reacting is increased, when the concentration is increased. E.g.; Lower concentration Higher concentration Prediction: I believe that the rate of reaction will increase with increase in concentration. This is because as explained above. The higher the concentration, the more liquid (acid) particles there are in the same volume, to react with the solid (calcium carbonate) particles. Therefore the rate of reaction increases. Basically, at higher concentrations, there are more molecules per litre, so there will be more collisions, so the reaction rate should be higher at the same temperature. Doubling the concentration should double the reaction rate. However for some reactions, the rate may be proportional to the concentration squared. For some reactions it can even be proportional to the concentration to the power 1.5 The Kinetic Rate Law defines the relationship between concentration and reaction rates. According to the law, the rate is directly proportional to the molar concentrations of each reactant in the rate-determining step of the reaction mechanism; each raised to a power equal to their rate order. ...read more.

Middle

Of Gas Given off 50.0 39 40.10 29 30.20 21 20.30 5.5 10:40 2 Both set of results shown above, show that the amount of gas given off (cm3) decreased with the decrease in concentration. The amount of gas given off was directly proportional to the concentration. The reason for this is that, the higher the concentration, the more liquid (acid) particles there are in the same volume, to collide and react with the solid (calcium carbonate) particles. Therefore the rate of reaction increases. Basically the probability of the particles colliding and reacting is increased, when the concentration is increased. Evaluation My results were quite accurate, as you can see from my graphs. They show that the rate of reaction is directly proportional the concentration of the hydrochloric acid. As you can see from the graphs I've done on each concentration ratio, showing both experiments. There is quite a difference between the results of each experiment in some cases. Such as concentration 40:10(0.8M). The results are the same for both experiments up until twenty seconds after that they start to vary by about two degrees and eventually by four degrees. This means that I cannot accurately determine the overall rate of reaction for the concentration 40:10. The same happened for the concentration 30:20. After 140 seconds there was a difference of one hundred and forty degrees. This means that for this one also, I cannot accurately determine the overall rate of reaction for the concentration 30:20. ...read more.

Conclusion

Method 1. Obtain five 250-mL beakers, about 30 ml of hydrochloric acid solution, and about 80 ml of sodium thiosulfate solution. 2. Label the beakers from 1 to 5. 3. Add the amounts of sodium thiosulfate solution and distilled or deionized water to each cup indicated in the following table: Beaker Number Volume of Sodium Thiosulfate (ml) Volume of distilled or deionized (ml) 1 25 0 2 20 5 3 15 10 4 10 15 5 5 20 * Note that the total volume in each beaker is 25 ml. * Make a table that shows the information in the table above and also includes a column for time (sec) and relative rate (sec-1). * Make a small "x" on a sheet of white paper with a pencil. * Place a beaker containing the sodium thiosulfate solution over this "x." Add 5 ml HCl solution and begin timing the reaction as soon as the acid touches the sodium thiosulfate solution. * Stir the reaction mixture at a constant rate throughout the reaction. * Stop timing when the "x" under the beaker is no longer visible through the solution. * Record this time in your data table. * Repeat steps 2-4 for the remaining samples. This is another way of finding how concentration affects the rate of reaction. It is generally less accurate than my original experiment. I could extend my investigation further by doing the same experiment as my original one.But changing the calcium carbonate for other substances to find out which substances react directly proportionally to the concentration of the HCl and which are proportional to the concentration squared or to the concentration to the power of 1.5. ...read more.

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