Ahmet Tuğrul AKKUŞ 18.10.2011 11-B 103 Design Research Question By which methods can we separate anions and cations of different compounds in chemistry? Procedure Apparatus 1)9 test tubes 2) Test tube rack 3) Gloves 5) Lab coat 6) 0.2 M solutions of anions (NaCl, KI, Na2CO3, Na2SO4, NaNO3), cations (AgNO3, Cu (NO3)2, Pb (NO3)2, Fe (NO3)2) 8) Stirrer 10) Silver nitrate solution (0.5 M) 12) Sodium hydroxide solution (0.5M) 14) Barium chloride solution (0.5 M) 15) Magnesium nitrate solution (0.5M) 15) Aluminum foil 17) Beakers 18) Bunsen burner 19) Tripod 20) Wire gauze 21) Fume cupboard In this experiment anions and cations are going to be analyzed and separated. 0.2 M anions Cl- , I-, (CO3)-2, (SO4)-2, (NO3)-1 and 0.2 M of Ag+, Cu+2, Pb+2, Fe+2 cations are set to be identified. At the beginning of the experiment, anions and cations will be set as separated from each other. Lab coat and gloves are used for safety. There were 5 anion solutions and 5 labeled test tubes were used for the experiment. Samples were taken from the Erlenmeyer flasks by pipette. First nitric acid was used to acidify anion solutions, then silver nitrate solution is added to the test tubes, so the one containing chloride ions will form a white precipitate composed of silver chloride. Also the one containing iodide ions will form silver iodide which is a yellow solid precipitate. Magnesium nitrate is added to remaining test tubes and the one containing carbonate ions will form magnesium carbonate which is a white solid precipitate. Then remaining anions are sulphate and nitrate ions. To the remaining test tubes barium chloride solution is going to be added so the test tube containing sulphate ions will form a barium sulphate which is a white precipitate. Remaining unidentified sample is (NO3)-. Test tube is poured into a beaker then a little sodium hydroxide and aluminum foil is added to the solution and it is heated on Bunsen burner carefully. This process must be carried in a fume cupboard since ammonia is given off. Then while heating the sample, a litmus paper is held into the mouth of the test tube and a color change from red to pink is observed and it is a proof of the existence of nitrate ions in the solution. Now it is time for cation group. The test tubes were labeled as in the order they were taken from the Erlenmeyer flasks by pipette. A few drops of dilute sodium hydroxide is added four test tubes. Cu+2 form a pale blue precipitate as copper (II) hydroxide is insoluble in water. Also Fe+3 form a red brown precipitate with dilute sodium hydroxide. Pb+2 formed a white precipitate with a few drops of dilute sodium hydroxide and Ag+2 form a light brown precipitate with sodium hydroxide solution. It is better to gather the data in two tables for cations and anions TEST TUBES 1) 2) 3) 4) 5) ANIONS Chloride Iodide Carbonate Nitrate Sulphate All anion samples were identified successfully by the method described above. TEST TUBES CATIONS 1) Ag+2 2) 3) 4) Cu+2 Pb+2 Fe+3 All cation samples were clearly identified and all expected precipitations was observed so the cations in the test tubes follows as the table above. As a conclusion all of the samples were identified successfully because they all gave the expected reactions with the known solutions. Solutions were not prepared with sensitivity because as the experiment did not include any graphical data or graphical interpretation but just to show the presence of the anions and cations, the concentration of the solutions were not considered important as it will not change the result of the experiment. It was same for the amount of samples taken by each Erlenmeyer flask; we did not measure the volume of sample taken from the Erlenmeyer flasks for the same reason. Calculating the concentration of all the solutions that had been prepared would be a good improvement for the scientific being of the experiment and also the volume of sample taken from each Erlenmeyer could be measured for the welfare of the experiment. Another improvement could be repeating the experiment by using other kind of solutions that would have different identifications for anions and cations so that we could support our answers by two different experiments. At the beginning of the experiment, the research question was “By which methods can we separate anions and cations of different compounds in chemistry?” and the answer to the question is to use displacement reactions taking place between any ion in the solution and the solution being added and making sure that the new compound does not dissolve in water and forms a precipitate so that it is easier to identify the substance.