The Rate of Reaction When Different Concentrations

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I am investigating how the rate of reaction differs when we change the concentration of Hydrochloric Acid whilst reacting with Magnesium. The rate of reaction is explained by the Collision Theory. This theory explains how various factors affect the reaction rates and how chemical reactions occur. The 4 factors of the Collision Theory are: •Temperature

Concentration
Surface area
Catalyst
I am investigating how different concentrations of acids affect the rate of reaction. However I must control the temperature, surface area and catalyst by keeping them the same throughout the experiment. I used 5 different concentrations of acid. These were, 2.0(mol), 1.6(mol), 1.2(mol), 0.8(mol) and 0.4(mol). The reason I used such a variety of acids was to make sure my results were more reliable and to ensure I got wider range of results. I kept the temperature at room temperature and the surface area of the solution always added up to 40cm3. The magnesium was cut to 4cm each time I did the test. I kept these three factors the same to make it a fair test and to ensure my results were more reliable. I didn’t use a catalyst as it speeds up a reaction and my reaction was fast enough without using it. I used a wide variety of different concentrations so I was able to see what effect it had on the rate of reaction. It also showed a positive correlation on my graph which helped me interpret my results. I did a preliminary test (practice test) to see how we would construct each experiment and who would do what jobs, for example marking the gas produced or timing every two seconds of the reaction. It also helped me to find out how many seconds I should mark the amount of gas produced. I started off with 4 seconds but for the 2.0(mol) concentration the reaction was fast, so I marked every two seconds instead to get a more reliable result. Doing the preliminary test help make my final experiment more accurate and reliable. To ensure my results were reliable I repeated each test three times which helped me identify any outliers and if I had any I did the test again. This also made my results more accurate. For this experiment I used the following:

A conical flask
A gas syringe
A measuring cylinder
A rubber bung
A stop clock
Magnesium
Stand and clamp
Hydrochloric Acid
Ruler
Scissors
Black marker
Water

I used a conical flask which contained the solution of acid and Magnesium, a gas syringe to measure the amount of gas produced a measuring cylinder to measure the correct amount of water and acid. I used a rubber bung to trap the gas produced and a delivery tube which was attached to the rubber bung that collected the gas. The gas travelled through the delivery tube and was collected in the gas syringe and I then marked off the amount of gas collected every two seconds. I used scissors to cut the 4cm of Magnesium. Collecting Data

When collecting my data I came across some anomalous results (outliers). When this happened we repeated the test again to discard the previous outliers and get our results more accurate as we might have marked the amount of gas produced wrong. I came across many problems when collecting my results. One of many being on time and accurate when taking the readings of the amount of gas produced every two seconds. This was a problem for me as two seconds went very quickly and the gas produced was increasing rapidly, making it harder to mark the amount accurately. Another problem was putting the bung on the conical flask immediately. It was important to do this as my results would have been affected if any gas escaped. Interpreting Data

My graph shows that the higher the concentration of acid the faster the reaction. I also calculated the gradient and this shows that my highest gradient was 2.0(mol) which was 7.14. This was higher than 1.6(mol) which was 5. 1.6(mol) was higher than 1.2(mol) which was 3. This was higher than 0.8(mol) which was 1.79. Finally,...
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