IB Chemistry Lab Design †compare the effect of temperature on the concentrations of Vitamin C and Vitamin A in solution Essay

Research QuestionTo correspond the effect of temperature on the densitys of Vitamin C and Vitamin A in firmness of purpose.Background disciplineMany researchers claim that the vitamin content in the food we eat decr liberalisations as we cook the food, since it is being exposed to high temperatures. This really intrigued me since cooking is ace of my hobbies, and I always try and check the nutritional value of meals that I cook.With this in mind, it was quintessential for me to see for myself if these claims hold true. To narrow the scope of the investigation, I chose Vitamins A and C to do this study upon.The claims state that the enzyme in whose form Vitamin C is found, gets denatured (or oxidised) at temperatures over 70C as well as at low temperatures, in the freezer. Also, studies claim that Vitamin A (in the form of retinol) gets oxidised at high temperatures, during cooking. Once these vitamins get oxidised, they are lost to us. This investigation will compare the effects of high temperature on Vitamin A and Vitamin C firmness of purposes.http//chemmovies.unl.edu/chemistry/smallscale/SSGifs/SS054Ascorbic.gifThe ascorbic stinging enzyme gets denatured at high temperatures because the tertiary structure of the protein, which the enzyme is made up of, unravels, ca utilize the active site of the enzyme to convert in shape. This leads to the substrate being unable to fit into the active site, and we say that the enzyme is denatured. This denaturing evict take place at extremes of pH too.The Vitamin A (retinol) gets oxidised because, at high temperatures, it reacts with oxygen in the air to form a carboxylic acid (retinoic acid).In the laboratory, ascorbic acid found in fruits and vegetables can be simulated by tack oning ascorbic acid crystals to wet, to form a mildly acidic dissolvent. This solution can also be used as the standard solution during titration to find niggardness of ascorbic acid. To simulate Vitamin A, we can simply add retinol to water to form a standard solution.HypothesisAt higher temperatures, both the stringency of Vitamin C and Vitamin A can be expected to decrease. However, I expect the decrease to be greater in the event of the Vitamin C solution since (having protein-like properties) it is more(prenominal) sensitive to extremes of temperature. Also, the alcohol retinol has a high boiling point, so I believe that it will be more resistant to oxidation too.VariablesIndependent VariableWhy and How it is ChangedTemperature to which the Vitamin C/A solution is heatedThe factor whose effect is being studied on the niggardness of Vitamin C/A in a solution is the temperature the solution is heated to. Therefore, the temperature is the independent variable. In order to change the temperature, equal quantities of the identical Vitamin C/A solution are heated to different temperatures. The different temperatures taken are 30C, 50C, 70C and 90C. As a control, one solution is placed at live temperature. A thermometer is used to measure the temperature of the solution. Investigation at each temperature will be repeated 3 times, to go over reliability.Dependent VariableWhy and How it is RecordedConcentration of Vitamin C/A in solution (in mol dm-3), after exposure to temperatureThe effect of temperature on the concentration of Vitamin C/A in a solution is being studied, thus the concentration is the dependent variable. As the temperature moves further away from room temperature (above or below) the concentration of Vitamin C/A in the solution should decrease due to denaturing or oxidation. The concentration of Vitamin C is work out by doing an single titration. A starch solution is added to a standard Vitamin C solution which is the titrant. Into this, a solution of potassium iodide and potassium iodate is titrated till a blue colour is obtained (end point). This is repeated thrice. The average batch of iodine solution used is calculated, and divided by the concentration of Vitam in C.Then, the solutions of unknown concentrations are titrated and unitary method is used to calculate their concentrations. The concentration of Vitamin A is calculated using a redox titration. This is done by making a solution of acid dichromate, potassium iodide and starch. This is titrated against a solution of sodium thiosulfate of known concentration. The slew of thiosulfate used is noted. Then, the Vitamin A solutions are added to a similar solution of dichromate, KI and starch, and titration is carried out with thiosulfate. For every 1 less rampart of thiosulfate used there is 0.25 mole of alcohol in the sample (according to the chemical equations) which was tested.Controlled VariableWhy and How it is MaintainedpH of Vitamin solutionExtremes of pH can also lead to the denaturing of enzymes, so if pH changes it will interfere with the results, potentially giving inaccurate results. Thus, the pH needs to be kept a constant. This can be done by adding a few drops of acidic b uffer to the initial solution.Presence of AntioxidantsAntioxidants including salts such as sodium chloride tend to protect ascorbic acid from being oxidised, and thus their presence whitethorn lead to inaccurate results. Thus, they need to be eliminated. This can be done by using distilled water (without any salts) while preparing the solution of ascorbic acid.Head dummy Present in SystemThe ascorbic acid gets denatured because of oxidation by air. Thus, if the volume of air present in the system changes, the results will also change invariably. To prevent this, the amount of head space present in the system must be kept constant. This can be done by placing a lid on top of the beaker in which the acid solution is heated.Initial Concentration of Ascorbic Acid solutionIf the initial concentration of ascorbic acid in the solution is different, thus the final concentration will also be affected. This can be avoided by adding the same mass of ascorbic acid to the same volume of water while preparing all the sample solutions.Volume of Ascorbic Acid solutionThe volume of acid solution used for each temperature and each running game should be the same since otherwise it will affect the volume of iodine solution used. Therefore, the volume has to be measured accurately using a pipette for each temperature and trial (each titration).Concentration of starch, potassium iodide and potassium iodate solutionsThe concentration of any of these solutions will affect the volume of solution titrated during each trial. Thus, it needs to be kept a constant. This can be done by ensuring that equal masses of these reagents are added to equal volumes of water, for all the trials.Final temperature of solutionThe final temperature of the solution may affect the concentration of the acid in the solution, as rapid heating and cooling can encourage oxidation. Thus, to avoid errors, the solutions will be allowed to rest till they reach room temperature, and only then will they be titrat ed to calculate concentration.Chemicals1. L-ascorbic acid 3.52 g to make 1 dm3 of 0.002 M solution of acid1. Glucose 50 g to add to acid solution, to simulate fruit juice1. Potassium Iodide 10.0 g to make 1 dm3 iodine solution1. Potassium Iodate 0.536 g to make 1 dm3 iodine solution1. Starch (soluble) 0.25 g to make 50 ml of 0.5% starch solution1. 3.00 M Sulphuric Acid 60 ml to add to iodine solution1. Distilled Water To make all the solutions and washingOther Materials1. Weighing Scale1. Bunsen Burner1. Tripod Stand1. Wire Gauze1. Mortar and Pestle1. pipette Filler1. Lid (for beaker) 41. ThermometerProcedurePreparing Ascorbic Acid Solution of concentration 0.002 M1. Measure 3.52 g of L-ascorbic acid using the weigh scale and the weighing boat (which has to be completely dry).1. perplex the weighed crystals in the mortar and use the pestle to crush the crystals into a fine powderize, to aid with dissolving it in water.1. Place the powdered acid into a euchre ml beaker a nd add a little distilled water to dissolve the acid. map the glass rod to stir.1. Once it seems that the acid has fully dissolved, add some more water to the solution, to ensure that all the acid has actually dissolved. Then, transportation system the solution into the 1000 ml standard flask using a washed funnel and the glass rod.1. Wash the beaker with water and pour into standard flask, to come to any remaining solution. Repeat this process 3 times.1. Wash the funnel and the glass rod, letting the water run into the standard flask.1. Make up the solution to the 1000 ml mark. Place the stopper and pleat the solution thoroughly. Transfer approximately 500 ml of this solution to the 500 ml beaker, for ease of use.Preparing the 0.5 % starch solution1. Measure 0.25 g of starch using the weighing scale and weighing boat.1. Bring 50 ml of distilled water nearly to a boil, and then add the measured quantity of starch powder to it. Allow to cool.Preparing the Iodine Solution1. Measu re 10.0 g of potassium iodide and 0.536 g of potassium iodate using the weighing scale and weighing boat. Transfer this to a 500 ml beaker.1. Dissolve the solids in approximately 400 ml of distilled water. Stir using the glass rod, to aid in dissolving. Add the 60 ml of 3.00 M sulphuric acid to the solution at this point.1. Once it seems that the solids have fully dissolved, add some more water to the solution, to ensure that all of it has actually dissolved. Then, transfer the solution into a 1000 ml standard flask, using a washed funnel and the glass rod.1. Wash the beaker with water and pour into standard flask, to remove any remaining solution. Repeat this process 3 times.1. Wash the funnel and the glass rod, letting the water run into the standard flask.1. Make up the solution to the 1000 ml mark. Place the stopper and mix the solution thoroughly. Transfer approximately 500 ml of this solution to a 500 ml beaker, for ease of use.Titration Set-up and Final Steps1. Transfer 65 m l of Vitamin C solution each into 5, 250 ml beakers.1. Keep one of the containers in a trough containing resolve ice (0C). Keep one at room temperature (as a control + standard solution). Heat the other three to 30C, 60C and 90C respectively. Ensure that all the beakers are covered with a lid during heating or cooling.1. Wash the pipette, first using tap water and then distilled water. Rinse the pipette thoroughly with the Vitamin C solution at room temperature.1. Use a pipette to transfer 20 ml of the Vitamin C solution, at room temperature, into a conical flask. This is the standard solution (and the control) since its concentration is known (0.002 M).1. Add 10 drops of the starch solution to the conical flask. Swirl the contents to mix properly.1. Wash the burette with tap water followed by distilled water. Then, rinse the burette with the iodine solution.1. Fill the burette with iodine solution till the 0.0 ml mark.1. titrate the iodine solution into the conical flask, swirling the conical flask at all times. The end point is reached when a blue colour is obtained that persists even after 20 seconds of swirling. Note down the volume of iodine solution used.1. Re-fill the burette to the 0.0 ml mark. Repeat the titration process 2 more times. Note down these two determine for volume of iodine solution used as well. Calculate the average volume used.1. Check that all the solutions that were heated (or cooled) have reached room temperature, with the help of a thermometer.1. If they have reached room temperature, repeat the entire titration process (steps 18 24) with the other 4 solution (0C, 30C, 60C and 90C). Ensure that the burette is re-filled to the 0.0 ml mark after each and every titration, and that the pipette is first washed, and then rinsed with the solution that is going to be placed in the conical flask.1. Use unitary method, to calculate the concentration of Vitamin C in each solution, after heating or cooling, using the concentration of the sol ution at room temperature (0.002 M) as the known value.