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# Investigate whether changing the molar of hydrochloric acid affects the rate of reaction when it is added to calcium carbonate chips.

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Introduction

Aim Our aim is to investigate whether changing the molar of hydrochloric acid affects the rate of reaction when it is added to calcium carbonate chips. Prediction/ Hypothesis I predict that the higher the molar of acid the faster the rate of reaction will be with the marble chips. This is because with a higher molar of acid there will be more acid particles to collide with the calcium carbonate, therefore causing a reaction in a faster time. With a lower molar of acid there will be more water molecules, resulting in the less chance of collisions with the calcium carbonate. In the graph there should be a gentle curve in the line of best fit as the molar decreases. Independent variable This will be the variable that I am changing in the experiment. The easiest variable to change and the one probable to give the most accurate results is changing the molar of the hydrochloric acid. I am going to make up different molars of acid by adding water to a 3M acid. My molars will range from 3M to 1M, these will also include 1.5M and 2.5M. Using these molars I hope to achieve a good range of results and a good graph. I will make up the different molars using these formulae: 2.5 molar - 25cm� HCL + 5cm� H20 2 molar - 20cm� HCL + 10cm� H20 1.5 molar - 15cm� HCL + 15cm� H20 1 molar - 10cm� HCL + 20cm� H20 Dependent variable This will be the variable that I am measuring. ...read more.

Middle

I have decided to use a mass of 10g marble chips. If the mass is not kept constant on all the experiments, we can expect the averages to be incorrect. If there is more chips used the reaction time will be shorter because there is more chips for the acid to collide with. If there are less chips the reaction time will be longer, because there will be less chips for the acid to collide with. I will make sure that the mass remains the same, by weighing the chips for each test on an electronic balance. Volume of hydrochloric acid - if there is a greater volume of acid in the tests, the reactions times will be shortened, because there will be more acid particles to collide with the chips. The amount of acid I have decided to use is 10cm3. I have chosen this because it will be easy for me to make up the molars. To make sure that I keep this the same I will accurately measure out the acid in a measuring cylinder. Size of marble chips - this is something we must take into consideration, although we do not have much control over it. A large chip size will react faster because it has a larger surface area. Molar of the acid - even though we are changing the molar in this experiment, it is very important that the molar stays the same. ...read more.

Conclusion

molar - 20cm� HCL + 10cm� H20 1.5 molar - 15cm� HCL + 15cm� H20 1 molar - 10cm� HCL + 20cm� H20 Diagram Results table MOLAR TEST 1 TEST 2 TEST 3 AVERAGE 3 6.62 7.01 7.14 6.9 2.5 9.41 10.87 11.12 10.47 2 15.02 15.37 15.15 15.18 1.5 20.7 29.95 44 48.21 1 133 79.18 228 146.7 Conclusion My predictions that I made were correct, and are supported by my results and graph. The graph is significant indication in the relation between affecting the molar of acid. The line of best fit shows that there is a dramatic drop between the time it takes for the acid to react with the marble chips on the 1 and 1.5 molar, but then the decrease slows down and becomes more gradual. Evaluation If I had more time I would like to of made more tests to improve the average, also I would of liked to of tested a wider range of molars to see if the decrease in reaction time is more or less dramatic with higher molars. I thought we conducted the experiment very well and efficiently, however, we did have some anomalous results in several of the molars, this may have been down to a number of variables as described earlier in the exploration; such as concentration of the acid. We ignored these results and repeated the test when we came across them, with this the anomalous result did not appear again. ...read more.

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