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To see how the concentration of acid, reacting with potassium carbonate, affects the rate of reaction

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Aim: To see how the concentration of acid, reacting with potassium carbonate, affects the rate of reaction. Intro: This is the reaction I am using in my coursework: 2HCl + K2CO3 CO2 + 2KCL + H2O In order for substances to react together the particles in the substances must collide with each other and the collision must have enough energy. If there isn't enough energy, no reaction occurs. If there are lots of successful collisions then a lot of CO2 will be produced. The rate of a reaction depends on how many successful collisions there are in a given unit of time. A reaction can be made to go slower or faster by changing the concentration of a reactant. Acid particle Water molecule Potassium carbonate tablet 1 2 In dilute acid, there are not so many acid particles (see diagram 1). This means there is not much chance of acid particles hitting a potassium carbonate particle. In a more concentrated solution of acid, there are more acid particles (see diagram 2). There is now more chance of a successful collision occurring. Concentration is how much of a substance there is in a certain volume and is measured in Moles per litre of solution (M). The concentration of a solution is the amount of solute, in grams or Moles that is dissolved in a litre of solution. That is what my coursework is mainly about. I predict that on my graphs for the results I get directly from the experiment, the curves will bend from a vertical line to a horizontal line and the faster the reaction the steeper the curve will start and the quicker it will reach a horizontal line. ...read more.


This is because the water made the numbers on the measuring cylinder blurred so I could not read them. 110 - 120 - I am glad I carried out some preliminary tests because they showed that there were problems of how the experiment had been setup. I corrected the experiment using the mistakes from the preliminary tests: I got a large measuring cylinder instead of a small one and I emptied some of the water out of the large plastic beaker. Results: 20cm3 of hydrochloric acid with no water added: Time (seconds) CO2 (cm3) 1st try CO2 (cm3) repeat 10 12 20 20 21 30 30 31 40 40 40 47 50 46 58 60 55 66 70 61 70 80 69 82 90 73 86 100 77 88 110 81 91 120 84 93 130 86 95 140 87 96 150 88 97 160 90 98 170 91 98 180 91 98 190 91 98 I carried out a repeat of this experiment just to make sure I was heading in the right direction with my results. They are all more or less the same so it is all right. 20cm3 of hydrochloric acid with 5cm3 water added: Time (seconds) CO2 (cm3) 10 13 20 22 30 30 40 37 50 45 60 52 70 57.5 80 63.5 90 69 100 72 110 75 120 79 130 80.5 140 82 150 82.5 160 83 170 83 180 83 190 83 20cm3 of hydrochloric acid with 15cm3 water added: Time (seconds) CO2 (cm3) 10 10 20 13 30 16 40 22 50 26 60 30 70 35 80 37 90 42 100 45 110 46 120 46 130 46 140 46 150 46 20cm3 of hydrochloric acid with 20cm3 water added: Time (seconds) CO2 (cm3) ...read more.


This is because I must not have read it incorrectly as such, just made the mistake of, in each case, having the measuring cylinder at different angles, because I did not hold the measuring cylinder, just let it lean against the side. This is a mistake I would correct next time by maybe having another clamp to hold the measuring cylinder upright, making it a fair test. To solve the problem I would maybe use a gas syringe or I would use a set of better apparatus so the measuring cylinder would stand vertically so it would be easier to read. This is a problem because in the first attempt some of the CO2 dissolved in the water. This will have meant the gas doesn't get collected overall plus the reaction looks slow at the start because the gas is too busy dissolving to go into the measuring cylinder. This means that in the second attempt the gas did not dissolve so these problems did not occur, so the results were different. The reason for this is that - Before I started the second try I forgot to empty the water from the large plastic beaker and the large measuring cylinder. To cure this problem, next time I would consider using a gas syringe so there is no water for the gas to dissolve in. When I started each individual test there was always a couple of second between starting the timer and dropping the tablet in the acid. This is quite a big problem because in that time you could miss an amount of gas and so changing the start in each of my results. To rid the tests of this problem I would get some help from a classmate so the time difference from dropping the tablet in to starting the timer is reduced significantly. ...read more.

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Here's what a teacher thought of this essay

4 star(s)

This is a good experiment with valid results and a suitable conclusion. It does, however, appear to be missing the graphs that are mentioned in the report. It covers a simple topic and would be suitable for a lower ability pupil to read.

Overall, this piece of work would be 4 out of 5 stars.

Marked by teacher Brady Smith 13/08/2012

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