Analysis of Solutions Containing Essay

This experiment continues the qualitative analysis begun in Experiment 19. Here we lead be analyzing effects to go out the social movement of anions. The identical techniques that were used for the cation analysis must be used for the anions. If you have non carried out Experiment 19, read the introductory section before scratch this experiment. The major difference between cation and anion analysis is that in anion analysis, a serial publication of separations of the ions from one another is usu solelyy not the most efficient course to determine their comportment. Instead, only some separations impart be made, and the initial streak termination will be used to audition m either of the ions. constitute to the flow chart at the end of the experimental directions as you proceed. eldest you will prepare and analyze a known stem which contains all six of the anions. Then you will analyze an unusual solution use the same techniques, to determine the nominal head or absen ce of each anion. about of the acids and bases used are very concentrated and squeeze out wee-wee chemic burns if spilled. Handle them with care. Wash acid or base spills clear up of yourself with lots of water. Small spills (a few drops) can be cleaned up with penning towels. Larger acid spills can be neutralized with baking soda, NaHCO3,and accordingly safely cleaned up. Neutralize base spills with a vinegar solution (dilute acetic acid). Some of the compounds are poisonous. Wash your hands when finished.Solutions containing flatware grey ions and potassium permanganate solutions cause stains which do not appear immediately. If you suspect that you spilled any of these solutions on yourself, airstream off with soap andwater.Wear chemic Splash Goggles and a Chemical-Resistant Apron.Preparation of a Solution for Analysis.Prepare a known solution containing 1 mL of each of the anions to be runninged. This solution will be referred to as the cowcatcher establish solution. Your teacher will extend you with an undiscovered solution to be analyzed.Note that the following directions are written for a known solution that contains all of the anions. An unknown solution will likely not diverseness all of the products described in this procedure. You shouldmake post of any differences as you analyze your unknown solution.Aqueous solutions of all of the anions to be studyed are color slight. The positive ion associated with each of the anions will be both sodium or potassium ion.1. Separation of the Halides (Cl-, Br-, I-) Confirmation of Chloride.The halides all form insoluble capital compounds. Silver chloride is a duster solid, silver bromide is pale cream-colored solid, and the solid silver iodide is light lily-livered in color.Cl-(aq) + Ag+(aq) AgCl(s)Br-(aq) + Ag+(aq) AgBr(s)I-(aq) + Ag+(aq) AgI(s)Silver chloride is the only silver halide that melt downs in 6 M ammonia, NH3, forming the colorless ion Ag(NH3)2+. If nitric acid, HNO3, is chann eled to a solution containing this ion, the ammonia in the complex reacts with hydrogen ions to form ammonium ions, and the silver recombines with the chloride ions which are button up array in solution.AgCl(s) + 2 NH3(aq) Ag(NH3)2+(aq)+ (aq)Ag(NH3)2+ (aq) + (aq) + 2 H+(aq) AgCl(s) + 2 NH4+(aq) stray 10 drops of the skipper test solution (or unknown solution) in a test tube. Test to see if the solution is caustic. If it is not, add 6 M acetic acid, HC2H3O2, dropwise with divine guidance until the solution is acidic. conduct 10 drops of 0.1 M silver process, AgNO3. A precipitate of AgCl, AgBr, and AgI will form. Centrifuge and move off the supernatant liquid. Wash the solid with 0.5 mL distilled water, centrifuge and discard the wash water. supplement 0.5 mL 6 M ammonia, NH3, to the precipitate. Stir to decompose any AgCl.Centrifuge, and pour the supernatant liquid into another test tube to test for chloride ion. refuse the precipitate of AgBr and AgI in a container provide d for disposal of waste solutions.Add 1 mL 6 M nitric acid, NHO3, to the solution containing the change state silver chloride. The solution will get heated and smoke from the reaction with the intemperance ammonia whether or not silver chloride is present. Test with litmus test or pH makeup to see if the solution is acidic. If it is not, add more HNO3 until the solution is acidic. The appearance of the white precipitate of AgCl in the acidic solution confirms the presence of chloride. 2. Separation and Confirmation of Bromide and Iodide.In acid solution, iron(III) ion, Fe3+, is a frail oxidizing broker capable of oxidizing the easily oxidise iodide ion to iodine. Bromide and other ions present will not interfere. The nonpolar iodine will preferentially dissolve in nonpolar mineral oil, where it can be identified by its criticize to violet color.2 I-(aq) + 2 Fe3+(aq) I2(aq) + 2 Fe2+KMnO4 is a stronger oxidizing agent than the iron (III) nitrate and will oxidize bromide, Br-, to bromine, Br2. Other ions present will not interfere. The nonpolar bromine can be extracted into nonpolar mineral oil where it can be identified by its characteristic yellow to embrown color.10 Br-(aq) + 2 MnO4-(aq) + 16 H+(aq) 5 Br2(aq) + 2 Mn2+(aq) + 8 H2O(l) spatial relation 10 drops of the original test solution (or unknown solution) in a test tube. Add 6 M HNO3 dropwise with stirring until the solution is acidic. Add 1 mL 0.1 M Fe(NO3)3 in 0.6 M HNO3 solution and stir. Then add 1 mL of mineral oil, spark plug the test tube with a cork stopper and vibrate for 30 seconds. The presence of a pale pink to purple color in the mineral oil level (the top layer) due to change state iodine confirms the presence of I- in the original solution.Draw the mineral oil layer off the solution with a capillary dropper and discard in the container provided for waste solutions. Add 0.1 M KMnO4 solution dropwise with stirring until the solution dust pink. Again add 1 mL mineral oil, cork an d shake the test tube for 30 seconds. The presence of a yellow to brown color in the mineral oil layer due to dissolved bromine confirms the presence of Br- in the original solution. Discard the solution in the container provided. 3. Confirmation of Carbonate.In acid solution, degree Celsiusate forms degree centigrade dioxide gasconade and water. The carbon dioxide may be seen as a slight effervescence. Carbon dioxide is less soluble in hot water than cold water.When carbon dioxide gas is passed through a saturated solution of atomic number 56 hydrated oxide, it readily forms aprecipitate of white barium carbonate.CO3 2-(aq) + 2 H+(aq) CO2(g) + H2O(l)CO2(g) + Ba2+(aq) + 2 OH-(aq) BaCO3(s) + H2O(l)If any guggles were formed when acid was added to the original solution, carbonate is probably present and carbon dioxide is being formed. A confirmation of the presence of carbonate involves reacting evolving carbon dioxide with barium hydroxide to form white, insoluble barium carbo nate.Place 2 mL of clear, saturated Ba(OH)2 solution in a test tube to be available for the test with carbon dioxide. Place 1 mL of the original test solution (or unknown solution) in a different test tube. Acidify this solution by adding 0.5 mL of 6 M HNO3. Place the tube in a hot water bath and assert to see if any gas bubbles form. Take a dry Beral pipette and squeeze the bulb deard. Place the tip of the pipet close to (but not touching) the surface of the liquid in the test tube and slowly plough the bulb to draw escaping carbon dioxide into the pipet. Put the pipet into thebarium hydroxide solution, and slowly squeeze the bulb, causing the gas in the pipet to bubble through the barium hydroxide solution. This procedure may be repeated. The fundamental law of a cloudy white precipitate of barium carbonate confirms the presence of carbonate ion in the original solution. 4. Confirmation of Sulfate.The test for sulfate is the ecesis of white, insoluble barium sulfate. This so lid is insoluble even inacidic solution.SO4 2-(aq) + Ba2+(aq) BaSO4(s)Place 0.5 mL of the original test solution (or unknown solution) in a test tube. Add 6 M nitric acid, HNO3, dropwise until the solution is acidic. Then add 0.5 mL 0.1 M BaCl2 solution. The formation of a white precipitate of BaSO4 confirms the presence of sulfate. 5. Confirmation of Nitrate.The test for nitrate involves the reduction of nitrate ions in basic solution to ammonia, NH3, using solid aluminum as the reducing agent. When the solution is heated, ammonia gas is liberated. The evolvingammonia gas will turn litmus paper from pink to blue.3 NO3 (aq) + 8 Al(s) + 5 OH -(aq) + 18 H2O(l) 3 NH3(g) + 8 Al(OH)4 (aq)Place 1 mL of the original test solution (or unknown solution) in a test tube. Add 6 M NaOH dropwise until the solution is basic, and then add 6 drops in excess. Use a Beral pipet to transfer the solution to the bottom of a dry test tube without getting the walls of the test tube unshakable with solutio n. Add the tip of a spatula of aluminum granules. Place a pocketable cotton plant wad loosely about halfway down the test tube, but not touching the solution. This is to prevent spattering of the solution onto the litmus paper. Hang a piece of moist red litmus paper (or pH paper) in the tube so that the bottom of the paper is close to (but not touching) the cotton. Nowwarm the solution in a hot water bath until it starts bubbling strongly. Be sure that the solution and the cotton do not touch the litmus paper. Allow the solution to cool. A slow color change (within 3 to 5 minutes) of the litmus from pink to blue, starting at the bottom and spreading to the top, indicates the evolution of ammonia and confirms the presence of nitrate in the original solution.DisposalYour teacher will provide a waste container for the solutions used in this experiment. The teacher will add solid zinc and some sodium sulfate to the waste collected. The substances may be safely disposed of using the me thod in the Flinn Chemical Catalog / Reference Manual, suggested disposal method 11 (procedure B). See the appendix. banterIn your laboratory discussion include answers to the following questions1. The confirmatory test for chloride ion with silver ion is the same chemical reaction used to confirm silver in the cation analysis scheme. Explain what the reaction is and how the initial precipitate is dissolved and reprecipitated. Use equations in your explanation.2. The procedure for chloride analysis makes use of the fact that AgCl can be dissolved in ammonia, but neither AgBr nor AgI will dissolve in ammonia. Look up the solubility products of AgCl, AgBr and AgI and show how their relative solubilities add with this fact.3. Refer to a table of standard reduction potentials to find the set for the reduction of Cl2, Br2, I2, MnO4-, and Fe3+. List the reduction reactions according to the E values. From the listing determine which of the halides can be oxidized by Fe3+ and which can be oxidized by acidic MnO4-.4. Explain why it is necessary to test for iodide by oxidation with Fe3+ before the test for bromide by oxidation with MnO4- is done.5. print separate oxidation and reduction half-reactions for the procedure used in the test for nitrate ions.6. In the nitrate test, why must care be taken to keep the moist litmus from coming in clashing with the cotton or the solution?