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Investigation to find out how concentration affects reaction rate.

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Investigation to find out how concentration affects reaction rate Aim To find out how the concentration of hydrochloric acid affects the rate of its reaction with solid calcium carbonate Hypothesis When hydrochloric acid is reacted with calcium carbonate the equation for the reaction is: CaCO3 (s) + 2HCl (aq) CaCl2 (aq) + H2O (l) + CO2 (g) I predict that the higher the concentration of the hydrochloric acid, the more carbon dioxide will be produced, as there is more hydrochloric acid for the calcium carbonate to react with. The rate of reaction depends upon how often and how hard the reacting particles collide with each other (they have to collide hard enough for a reaction to occur). The more collisions there are, the faster the rate of reaction becomes because although the success rate of the collisions does not increase there frequency does which will increase the frequency of successful collisions. The higher the concentration of a substance the more particles of it there are. In this case, if there is a higher concentration of hydrochloric acid there are more particles of hydrochloric acid. As there are more particles of hydrochloric acid, the chance that there will be a collision with a calcium carbonate particle is increased. ...read more.


This experiment also allows me to easily record my results - the gas syringe allowing me to make my results accurate. I can also collect all of my data within a few lessons. Before my actual experiment I conducted a trial, to see if my plan would work. I followed the description above in setting up the equipment and decided to measure the concentrations at 0.5 M, 1 M and 1.5 M. I chose these because they have a wide range - as do my chosen measurements. I also feel three measurements is a suitable number to test my plan. Concentration of acid (M) Time (s) 5 10 15 20 25 30 35 40 0.5 4 4 5 5 5 5 5 5 1 19 21 23 2 29 32 35 36 1.5 27 30 33 34 37 39 41 41 For the concentration of 0.5 M I did not put the cork on fast enough so much of the gas escaped. This was because I was attempting to start the stopwatch at the same time. I realised it would be easier if somebody assisted me in starting the stopwatch so I could put the cork on so minimal gas is lost. ...read more.


I have re-taken these for my final results but they are hyphened in the table: Concentration of acid (M) Time (s) 5 10 15 20 25 30 35 40 0.8 3 5 6 6 7 7 7 7 2 8 9 10 11 11 11 11 11 I believe these low levels of gas production resulted in myself putting the cork on the test tube too slowly. This resulted in too much gas escaping though the test tube so not enough was collected in the syringe. This experiment was a generally sound way of carrying out this investigation yet if I were to repeat it I would make a change. I would change they way the calcium carbonate was added to the hydrochloric acid as too much gas escapes this way. The calcium carbonate could be added through a tube which leads to the cork and that could then be sealed to ensure gas would not escape this way. Although the graphs were beginning to level off at 40 seconds it may also be interesting to continue the timing to 60 seconds to see if the gas production had ceased completely. On a higher level, this experiment could be conducted but with the concentration of hydrochloric acid could exceed 2 M and it could be investigated whether the pattern observed in this graph continues at higher concentrations. ...read more.

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