An Investigation to See What Effects the Neutralisation of Acids by Antacids In this experiment I will be looking at what affects the rate of reaction in a chemical reaction between Hydrochloric acid and commercial antacids. I will be looking at one of the Rates of reaction, surface area, to see if a smaller surface area does speed up a reaction. The reason that I became interested in this experiment is that I have been suffering from terrible indigestion of late and was wondering what would affect the efficiency of the tablets.
Indigestion is a common condition caused by excess (or too strong) acid in the stomach, using antacids, usually a salt containing either an earth or alkali metal, always a base, neutralises the acid in the stomach relieving pain. In chemical reactions atoms are rearranged. This rearrangement (and the reaction) is caused by the collision of atoms. In gases and liquids, contact with solids and with each other millions of collisions occur very second. If all these were successful and caused a reaction then every reaction would be over in a millionth of a second.
Because reactions aren’t over in such a quick speed one can presume that not all collisions are successful. To be successful a collision has to occur with enough energy and directly. A good analogy for this is bumper cars at a fair ground. A glancing hit does little but a head on collision hurts! Several things govern the rate of a reaction. I predict that as the surface area of one of the reactants (the tablet) increases so will the rates of reaction. This is because of the reasons discussed above. I set up the apparatus as below and used the equipment safely. 1.
I broke the tablet into smaller sizes as per the experiment demanded 2. In this experiment I will be using 0. 25-M hydrochloric acid because antacid tablets are designed to work in our stomach, in which is hydrochloric acid. I was provided with 2M hydrochloric acid and so diluted 2. 5mls of acid in 17. 5mls of water. I found that 0. 25M acid works best through some preliminary work. 3. a) When using the two smaller sizes I added 15mls of the water to the powder so I didn’t loose any reactants. b) When using larger surface area I just broke the tablets into their respective sizes.
4. I added the hydrochloric acid solution into the side arm tube and measured (in mls) how much was released by seeing how much water was displaced from the measuring tube. My results were as followed: My results contain one anomalous result. This occurs in the fifth minute of the 1/4 tablet experiment. It was more likely to have occurred by human error than contamination because the control was negative and it occurs half way through the test, not from the start. This graph shows the reaction between 0. 25m hydrochloric acid and Rennie antacid tablets.
As you can see the reaction starts at a steady speed and slows down as the reaction progresses. This is because the reactants are used early on and the amount of reactant available toward the end of the reaction is small. At the top end of the graph the speed of reaction between a 1/4 and a 1/6 is small considering the huge increase in surface area. This is because the increase in surface are no longer affects the rate of reaction; the rule no longer applies. This is common with scientific laws, such as Hooke’s law. Conclusion Antacid tablets are designed to neutralise stomach pH to stop heartburn and indigestion.
In my opinion my experiment went quite well. From my experiment one can see that the smaller surface area of a reactant the slower the reaction. This proves my prediction and the rates of reaction correct. The 1/6 tablet reacted far quicker than the whole one. There is little difference between the smallest two sizes of tablet, this is because the law starts not to apply. The pattern is that as the surface area increases so does the rate of reaction, up to a certain point. An anomalous result occurred in the 5th minute of the 1/4 tablet, but it think it was due to human error, as opposed to contamination.
I believe that contamination would have affected the whole test, and it would have stood out form the other results, having either a faster or slower reaction rate than the others. The best place to test the tablet would be in the stomach, as this is where the tablets are designed to work, it would be interesting to see if the enzymes in the stomach aid or slow down the reaction, although I think it would make little difference as the enzyme present in the stomach, protease, is designed to break down protein into amino acids, thus would do little to catalyse the neutralisation of stomach acid.
To obtain results closer to those which would occur in the stomach, the experiment would have to take place at 32i?? c. I would expect the reaction to occur at a faster rate, because the particles would be moving faster (this point is explained in further detail earlier in this report). The best way to obtain results similar to those that would occur in the stomach would be a computer simulation, this way I could set the testing environment how I wanted without having to obtain a stomach.