Science Coursework Essay
For my science coursework I have been asked to carry out an experiment to investigate the strengths of different sodium hydroxide solutions. By the end of my experiment I would like to find out which solution would be the best antacid to overcome indigestion. Indigestion is when acid from your stomach flows back up the oesophagus. I will be testing three sodium hydroxide (Na) solutions which have varying strengths, they are labelled A, B and C. To investigate the strength of each alkali I will use 4 different methods to measure the solutions.Phenolphthalein indicator is added to the antacid to turn it pink. Acid is added to the alkali solution to neutralise it. The amount of Acid which is added to each solution will determine the strength ness of it. Neutralisation is an irreversible chemical reaction; this is when an acid is neutralised by an alkali. This kind of chemical reaction produces reactants which are water and salt. The formula for this is: Acid + Alkali –> Salt + Water.The equation for this experiment will be:Hydrochloric Acid + Sodium HydroxideHCl (aq) +NaOH (aq) –> NaCl (aq) +H2O (l)Apparatus:1 x 250cm3 Beaker,1 x 200cm3 Beaker,Pipette Filler,Pipette,Conical Flask,Clamp,Clamp stand,Test tube,Test tube stand,Burette,Measuring cylinder.Sodium Hydroxide solutions A, B and C,Hydrochloric Acid,Phenolphthalein (Indicator),Water.Strategy:In order to make this experiment fair I will be using 4 different methods to measure the acid used to neutralise the antacid solution. I will be using test tubes, beakers, measuring cylinders and the burette/pipette. I will test the equipment to see which method produces the most accurate results. By the end of the experiment I will be able to identify which method is the best and therefore conclude which equipment formed the most precise outcomes.Method 1 (Test Tubes)1. Pour one test tube full of the Sodium Hydroxide into a beaker.2. Add few drops of indicator to turn it pink.3. Add little amounts of HCl from the test tubes, into the solution and wait until it turned colourless.4. Record how many test tubes of HCl it took for the solution to be neutralised.Conclusion of this method:By using this method I found it difficult to record the results accurately. I was unable to control my hand when the acid was being added to the alkali. This made my result unreliable because the correct readings weren’t taken as the solution turned colourless. Therefore I will not be assessing this strategy as there are many defects and creates unreliable results.Method 2 (Beakers)1. Pour 100cm3 of Sodium Hydroxide in to the smaller beaker.2. Add few drops of indicator to turn pink.3. Use the larger beaker to add the acid to the alkali. Wait till the solution turns colourless.4. Record how much HCl was added to the Sodium Hydroxide.Conclusion of this method:I think this strategy was reasonably reliable as there was more acid in the beaker than the test tube, so I was able to stop as soon as the solution went colourless. However due to human error I don’t think I got completely accurate results. Also as the graduations on the beaker were more spread out, me and my group couldn’t tell exactly how much HCl was added to the Sodium Hydroxide. We estimated most of the results for this method. Overall I think this method is undependable as the results won’t reflect the true outcomes of the experiment, therefore I will not be assessing this strategy.Method 3 (Measuring cylinders)1. Pour 100cm3 of Sodium Hydroxide into the measuring cylinder.2. Add few drops of indicator to turn pink3. Pour 100cm3 HCl into a measuring cylinder.4. Add HCl to Sodium Hydroxide until it turns colourless. Then record how much HCl was used and take it away from 100cm3Conclusion of this method:I think this method was very accurate because of the amount of graduations of the measuring cylinders. I was able to tell exactly how much acid was needed to neutralise the solutions. This slightly closed the gap for human error as the graduations were more reliable. However, it was difficult to pour acid from one cylinder to the other, sometimes a few drops of solution fell outside the measuring cylinder. This minor problem could affect the outcome of my results, therefore I will not be using this method.Method 4 (Burette & Pipette)1. Pour acid into smaller beaker. Pour Sodium Hydroxide into larger beaker.2. Pour acid into the burette up to 0.003. Using the pipette and pipette filler pour 25cm3 of Sodium Hydroxide into a conical flask.4. Add few drops of indicator to turn pink5. Turn the tap of the burette to pour the Acid into the conical flask. Wait till the solution goes colourless.Conclusion of this method:Because of the amount of gradients on the burette, I believe that this is the best method. My results were extremely reliable and I was able to obtain accurate results. There was very little room for human error as the tap enabled me to stop the acid as soon as the solution went colourless. So, I have decided to use this method because of the amount of accuracy.Experiment:Method 4 is the overall method I will use as I consider it to be the best experiment to find out which Antacid is the strongest.Here is how to carry out the experiment, step by step:1. Collect all the equipment which is needed-1 x 250cm3 Beaker,1 x 200cm3 Beaker,Pipette Filler,Pipette,Clamp,Clamp stand,Burette,Tile,Goggles,Sodium Hydroxide solutions A, B and C,Hydrochloric Acid,Phenolphthalein (Indicator),Water.2. Clean all the equipment thoroughly with distilled water to clean out any chemicals from previous experiments, (this will need to be done after using each Sodium Hydroxide solutions)3. Pour about 100cm3 of the first solution (A) into a small beaker. Then use a pipette filler to measure out 25cm3 of the Sodium Hydroxide solution. Empty the solution into a conical flask.4. Set up the clamp and stand and secure the burette to the clamp.5. Fill up the burette with acid and make sure there is no air bubble at the bottom by allowing the acid to run through.6. Record how much acid is in the burette. This will be the starting burette reading.7. Add a few drops of Phenolphthalein to the Sodium Hydroxide so it turns pink. Then place it on the tile, under the burette.8. Open the tap to allow the acid to flow into the conical flask. As soon as the solution turns colourless turn the tap so no more acid can fall into the solution (this will make the experiment more reliable and accurate).9. Record the final burette reading.10. Subtract the starting burette reading amount from the final burette reading to find out how much acid was required to neutralise the solution. Record this result.11. Rinse out the conical flask, and repeat the same experiment another 3 times as the first one is just a rough titration.12. After all titrations are done for one sodium hydroxide solution, clean all equipment thoroughly with water.13. Repeat the experiment 4 times for the remaining Sodium Hydroxide solutions (B and C)During this experiment I had to read a burette twice (at step 6 and step 9), reading a burette can be quite difficult. This is the right way to read it-A meniscus is curve that is at the surface of the acid when is formed when it is in a burette. The volume is read at the bottom of the meniscus. You always read the burette where the bottom of the meniscus is. For example-It is important to record the results accurately in order to get factual results.Here are three tables for each antacid I used in my experiment.Results:Antacid ARoughTitration 1Titration 2Titration 3Final Burette Reading26.3026.1026.5025.90Starting Burette Reading0.000.000.040.01Total Amount of Acid24.3026.1026.1025.80Average: 26.00 cm3Antacid BRoughTitration 1Titration 2Titration 3Final Burette Reading38.0038.9038.4038.40Starting Burette Reading0.010.020.000.00Total Amount of Acid37.9038.7038.4038.40Average: 38.50 cm3Antacid CRoughTitration 1Titration 2Titration 3Final Burette Reading53.5052.5053.7054.60Starting Burette Reading0.000.010.020.00Total Amount of Acid53.5052.4053.5054.60Average: 53.50 cm3For each antacid I repeated the experiment four times. The first one was always a rough titration. I did this to see if there is any problem with the results, and to see if everything is working precise. Then I can carry out the other 3 titrations correctly as I know that there will not be any problems with the equipment. Also I can compare the rough results to the other results to see if there are any outliers.Data Explanation:For each Antacid I worked out an average of all the experiments, excluding the rough titration.The average amount needed to neutralise the solutions were: A = 53.50 cm3B = 38.50 cm3C =Average: 26.00 cm3From the averages I can see that Antacid C was the strongest solution and therefore is the most effective, it was able to neutralise the most acid. This sodium hydroxide solution would be the best to treat indigestion.To work out the strengths of each antacid I can use this equation:Molarity of Acid xVolume of acid from titration/ Volume of Sodium Hydroxide solution.Solution A: 1M x 26.00/25= 1.04MSolution B: 1M x 38.50/25= 1.54MSolution C: 1M x 53.50/25= 2.14MFrom this I can tell that Solution C is the strongest alkali.Also I would like to look at the variation from the results of each antacid titration compared to the average.Antacid AFrom this graph I can see that the average is closer to two results and much larger than the last titration. This may show that a mistake could have occurred during the 3rd titration.Antacid BMy results for the 2nd solution varied. Two results were the same and the other was much more. The average was reasonably close to all three titrations.Antacid CThe average of this antacid solution is the same as one of the titrations. The titrations show a pattern, the solution reading at the end increased every time.Scientific Explanations:Titrations: An acid-base titration is a method in chemistry that measures the concentration of an unknown acid or base solution. It makes use of the neutralization reaction that occurs between acids and alkalis. A titration measures how much acid is needed to neautralise the alkali. Acid-Base titrations can also be used to find percent purity of chemicals.Indigestion: Indigestion (also known as dyspepsia) is a pain felt in the upper part of the abdomen underneath the rib cage. Indigestion occurs when there is damage of the mucous layer. Your stomach produces a strong acid that helps digest food and protects you against infection. A layer of mucous lines the stomach, oesophagus and intestines to act as a barrier against this acid. If the mucous layer is damaged, the acid can irritate the tissues underneath. It is caused by: not eating regular meals as acid levels can rise, smoking and excess drinking. The symptoms of indigestion are: pain in the abdomen, heartburn and loss of appetite. You could treat dyspepsia by using antacids. They can often relieve symptoms of indigestion by neutralizing acid in your stomach. Examples of antacid brands include Rennie and Mucogel, and many of the popular antacid brands contain a mixture of more than one active ingredient. However some antacids can create some Side-effects such as diarrhoea and constipation. Also some antacids contain an ingredient called which forms a barrier that floats on the top the stomach contents to prevent reflux.Evaluation & Conclusion:From my results and calculations I think my experiment went well. I did as much as I could to try and make the experiment fair and accurate however it was inevitable that a gap would be open for human errors. During my experiment my group always changed the person who was recording the amount of acid needed and the role of turning the tap when the solution turned colourless. This may have affected our results as different people observe things in different ways. Someone may have turned the tap too early or too late which would affect the outcome of our results. Also to make my results more firm, I could have repeated the experiment a few more times in order to get a range of results.Human error makes way for things such as, not rinsing out glassware properly, misreading the burette and not detecting the end point accurately. There are other methods that I could have tried out as well such as a pH meter. A pH meter is an electronic instrument used to measure the pH (acidity or alkalinity) of a liquid. A typical pH meter consists of a special measuring probe (a glass electrode) connected to an electronic meter that measures and displays the pH reading. This would have given me more accurate readings.However I think titrations was the best strategy out of all the methods I had tried. It was extremely accurate and only little mistakes could be made. Although I did find a few outliers during my experiment. The biggest outlier I found was the first titration of the whole expermint which was a rough one, the result outcome was 24.30cm whereas the other results were between 25.00-26.00. This may be because the equipment weren’t cleaned put properly or the results weren’t read accurately. To make my results even more accurate I could have redone them, however with such a small difference I did not feel that it was not necessary. If I wanted to have strong results I could repeat these experiments where there would not be any outliers whatsoever.In conclusion, I think I chose the finest method to find out which antacid is the best solution to cure indigestion according to the equipment which was available. I tested other strategies and came to a conclusion that they weren’t accurate enough. Using a burette and pipette, secured my results and made them extremely reliable. My experiment was carried out carefully and precisely in order to get a fair result. Overall I believe my experiment was triumphant, and by the end of it I found out which antacid successfully combats indigestion.