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How changing the concentration of an acid affects the rate of reation.

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How changing the concentration of an acid affects the rate of reation Prior Knowledge: Before embarking on this experiment, I already knew that metal carbonates react with acids to give off Co2 gas, e.g. Calcium Carbonate reacts with Hydrochloric acid to produce Calcium Chloride and Carbon Dioxide gas and water (This reaction shall be used in the main experiment). Therefore, I realised that I would be able to find the rate of reaction by collecting and measuring the volume of co2 gas produced at regular intervals. The balanced formula equation for the experiment is shown below: CaCo3(s)+2Hcl(aq) CaCl2(aq)+H20(s)+Co2(g) I also knew that there are many factors that affect the rate of reaction, e.g. temperature, pressure, surface area, the concentration of the acid and also, the adding of a catalyst. The factor that will be investigated in this experiment is the changing of the concentration of acid used. The experiment will be conducted at room temperature, as it was found to work well at this temperature in the preliminary experiments. The surface area of the marble chips will be kept constant. ...read more.


The more collisions with enough energy cause the rate of reaction to increase. Apparatus Top-Pan Balance Thermometer Gas syringe fitted with a delivery tube and rubber bung Retort stand and boss 100ml conical flask 50ml measuring cylinder 10ml graduated pipette Pipette filler Stopwatch Watch glass Weighing boat Chemical Flask 20.00g. of large marble chips Distilled Water 200 - 300 cm3 of 2M hydrochloric acid The rate of the reaction was found by dividing the concentration of acid by the time taken for the gas syringe to fill up with a certain amount of Co2. An example of this is shown below, where 1M acid concentration and a 90cm3 volume of gas were used. e.g. - 1/33 = 0.03 rate of reaction = 0.03 According to my results table and graphs, my data seems consistently reliable. However, on "Graph 1", one of the 1.5M points does not come into contact with the best-fit line and is, therefore, an anomaly. This is because of a human timing error which meant the result was slightly inaccurate. Graph Trends: An obvious trend can be seen on each graph. ...read more.


This is also shown on the second graph. The increasing steepness of the graph shows that, as the concentration of the acid increases, so does the rate of reaction. If the best-fit line or curve did not go through the origin, it would have been due to human error e.g. error reading the gas syringe. However, all of my lines did go through the origin, which again show a good degree of accuracy. If such error had occurred in my results, I would have repeated the experiment five times to eradicate these errors and justify my results. Even though I have no anomalies, I shall still repeat the experiment to ensure my results are accurate. To improve the experiment, I would swirl the marble chips in the Hydrochloric acid before inserting the bung. Taking everything into account, I have enough evidence to justify making a conclusion. Conclusion From conducting this experiment I have discovered that as the concentration of an acid increases, the time taken to collect a set volume of gas decreases. Also, as the concentration of acid increases, the rate of reaction increases. The experiment could be done again using a different acid e.g. Sulphuric acid, to show that all acids cause the same affect. ...read more.

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