Investigating Concentration and Rates of Reaction

Investigating Concentration and Rates of Reaction
Aim I aim to investigate the relationship between concentration of acid and the rate of reaction. Introduction It says in the oxford co-ordinated science, chemistry, second edition that "a reaction goes faster when the concentration of a reactant is increased." It also shows an example of an experiment to prove this statement. The experiment shows the reaction between magnesium and hydrochloric acid. In part of the experiment the acid is 0.5m, and then in the rest it is 1m. It is explained in co-ordinated science that the concentrated, 1m, reacted more quickly then the less concentrated, 0.5m. The reason for the 1m experiment reacting faster is because the particles are more reactive and so have more effective collisions, which means it reacts faster. Fair test and variables This experiment is going to take place in a science lab at edenham high school.
There will be a science teacher present to make sure everything is carried out safely. Each experiment will take place in the same science lab on the same day. This is to make sure that none of the conditions affecting the experiment will change. The variables are the amount of marble powder, amount of acid and the concentration of the acid. The only variable that will be changed is the concentration of acid; the amount of marble powder and acid will be kept the same. The amount of acid will be measured in center-meters-squared (cm) and the concentration measured in m. the marble powder will be measured in grams (g). I am keeping all variables the same except for the concentration, because it will make the experiment a fair test. For this reason I am also going to carry out the experiment three times, as it will make sure that the results are accurate. Apparatus Here is a list of the equipment I will need to carry out my experiment: ? 50ml of hydrochloric acid in different concentrations (e.g. 0.5m, 1m, 2m etc) ? 0.5g of marble powder ? 1 Beaker ? 1 Conical flask ? 1 Stand ? 1 Boss ? 1 Clamp ? 1 Scales ? 1 Timer ? 1 Gas syringe Here is a diagram of how to set up the experiment: Method Firstly all the equipment above most me assembled, and then set up like the diagram, also above. Wash out the conical flask and the measuring cylinder, before the experiment starts. 50 milliliters of hydrochloric acid should be measured out, using them measuring cylinder. Put the hydrochloric acid in to the conical flask. Measure out 0.5 grams of marble powder, using the scales. Add the marble powder to the hydrochloric acid in the conical flask, and seal the join to the gas syringe. Start timing the experiment as soon as the marble powder is added to the hydrochloric acid. Every thirty seconds check the amount of gas that has been produced, using the gas syringe. Carry on checking every thirty seconds until the gas has stopped being produced. Wash out the conical flask and repeat, twice more, with the same concentration of hydrochloric acid. Then repeat using a higher concentration of hydrochloric acid. Prediction -???- I predict that as the concentration of the acid goes up, the rate of reaction will also increase. So the higher the acid concentration the faster the reaction, and the lower the acid concentration the slower the reaction. I came to predict this because of the information I found using the oxford co-ordinated chemistry book. This showed that this is how increasing the concentration of acid affects the rate of reaction. Results Time in min 0.30 1.00 1.30 2.00 2.30 3.00 3.30 4.00 4.30 5.00 Concentration 0.5m 1 4 7 9 9 9 9 9 9 9 9 2 3 8 10 11 12 13 13 13.5 14 14 3 7 9 10 11 11.5 11.5 11.5 11.5 11.5 11.5 Average 4.6 8 9.6 10.3 10.8 11.1 11.1 11.3 11.5 11.5 1.0 1 10 12 13.5 13.5 15.5 15.5 15.5 18 18 18 2 10.5 13 16 16 16 16 16 16 16 16 3 6 8 8 11 11 11 11 11 11 11 Average 8.8 11 12.5 13.5 13.5 14 14 15 15 15 2.0 1 12 12 12 12 12 12 12 12 12 12 2 11 11 11 11 11 11 11 11 11 11 3 12 12 12 12 12 12 12 12 12 12 Average 11.6 11.6 11.6 11.6 11.6 11.6 11.6 11.6 11.6 11.6 Formula Calcium carbonate + hydrogen chloride à carbondioxide + hydrogencalside Analysis My graph shows that the rate of reaction does increase with concentration. You can tell this, because the line for the highest concentration evens out before the line for the lowest concentration. This shows that all the gas that can be made, is made quicker in the higher concentration then in the lower concentration. The fact that the line leveled out tells you that the gas has stopped being produced. So the further forward on the graph the line flattens out shows you how soon the gas stops being produced. Conclusion I conclude that my prediction was correct. As in my experiment proves that the higher the concentration of an acid the faster the rate of reaction. Evaluation The quality of my results is quite good and I am pretty sure that they are reliable. This is because I followed my method and took all precautions to make sure that the environment for each experiment was the same. So no environmental variables could affect my experiment. I could improve my method by, adding more repeats. This would make sure that the results were accurate. I could also add more concentrations of acid, to make sure that my theory still affects the rate of reaction with higher concentration. I could do another investigation, using a different type of acid (e.g. hydrofluoric acid) or a different material (e.g. chalk). This would see if my theory still affects the rate of reaction with different acids and materials. It would make the investigation wider, more reliable and give more evidence.

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