Analysis of Solutions Containing Essay

This try out continues the qualitative analysis begun in Experiment 19. Here we leave behind be analyzing beginnings to determine the aim of anions. The aforesaid(prenominal) techniques that were used for the cation analysis must be used for the anions. If you have not carried out Experiment 19, watch the introductory section before starting this experiment. The major difference between cation and anion analysis is that in anion analysis, a series of separations of the ions from one another is usually not the most efficient way to determine their presence. Instead, only if some separations strainament be made, and the initial mental trialing resolve go out be used to stress many of the ions. Refer to the flow chart at the end of the experimental directions as you proceed.First you impart prepare and discerp a known solution which contains all six of the anions. Then you will analyze an unknown solution using the same techniques, to determine the presence or absence of each anion. more or less of the demigods and bases used are very concentrated and can cause chemical burns if spilled. Handle them with care. rinse take acid or base spills off of yourself with lots of water. Small spills (a few drops) can be cleaned up with theme towels. Larger acid spills can be neutralized with baking soda, NaHCO3,and then safely cleaned up. subvert base spills with a vinegar solution (dilute acetic acid). Some of the compounds are poisonous. stifle your hands when finished.Solutions containing capital ions and potassium permanganate solutions cause stains which do not appear immediately. If you suspect that you spilled any of these solutions on yourself, wash off with soap andwater.Wear Chemical Splash Goggles and a Chemical-Resistant Apron.Preparation of a Solution for Analysis. conjure a known solution containing 1 mL of each of the anions to be tested. This solution will be referred to as the pilot burner test solution.Your teacher will provide you w ith an unknown solution to be analyzed. eyeshade that the following directions are written for a known solution that contains all of the anions. An unknown solution will probably not miscellanea all of the products described in this purpose. You shouldmake note of any differences as you analyze your unknown solution.Aqueous solutions of all of the anions to be tested are disguiseless. The positive ion associated with each of the anions will be either sodium or potassium ion.1. Separation of the Halides (Cl-, Br-, I-) Confirmation of Chloride.The halides all form non-water-soluble plate compounds. Silver chloride is a white loyal, silver cliche is pale cream-colored solid, and the solid silver iodide is sprightly yellow 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 dissolves in 6 M ammonia, NH3, forming the colorless ion Ag(NH3)2+. If nitrous acid, HNO3, is added 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 still present 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) mooring 10 drops of the passe-partout test solution (or unknown solution) in a test electron tube. quiz to see if the solution is sulfurous. If it is not, add 6 M acetic acid, HC2H3O2, dropwise with stirring until the solution is acidic. work 10 drops of 0.1 M silver nitrate, AgNO3. A sharp of AgCl, AgBr, and AgI will form. Centrifuge and pour off the supernatant suave. Wash the solid with 0.5 mL distilled water, centrifuge and discard the wash water. resume 0.5 mL 6 M ammonia, NH3, to the precipitate. nominate to dissolve any AgCl.Centrifuge, and pour the supernatant liquid into another test tube to test for chloride ion. incline the precipitate of AgBr and AgI in a container provided for disposal of drive away solut ions.Add 1 mL 6 M nitric acid, NHO3, to the solution containing the dissolved silver chloride. The solution will get resilient and smoke from the reply with the excess ammonia whether or not silver chloride is present. Test with litmus or pH paper 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 weak oxidizing means capable of oxidizing the easily oxidized iodide ion to tincture of iodine. Bromide and other ions present will not interfere. The nonionic iodine will preferentially dissolve in nonpolar mineral cover, where it can be identified by its pink 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 wil l not interfere. The nonpolar bromine can be extracted into nonpolar mineral oil where it can be identified by its characteristic yellow to brown color.10 Br-(aq) + 2 MnO4-(aq) + 16 H+(aq) 5 Br2(aq) + 2 Mn2+(aq) + 8 H2O(l) status 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, stopper the test tube with a cork stopper and shake for 30 seconds. The presence of a pale pink to purple color in the mineral oil story (the top layer) due to dissolved 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 remains pink. Again add 1 mL mineral oil, cork and 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, cokeate forms carbon dioxide gas 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 and through a perfect(a) solution of barium hydroxide, it readily forms aprecipitate of white barium lurch.CO3 2-(aq) + 2 H+(aq) CO2(g) + H2O(l)CO2(g) + Ba2+(aq) + 2 OH-(aq) BaCO3(s) + H2O(l)If any bubbles 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 carbonate.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 observe to see if any gas bubbles form. Take a dry out Beral pipette and squeeze the bulb closed. Place the tip of the pipet close to (but not touching) the surface of the liquid in the test tube and slowly release 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 convert is the formation of white, insoluble barium sulfate. This solid 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 plough 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 wet with solution. Add the tip of a spatula of aluminum granules. Place a small cotton sess loosely about ha lfway down the test tube, but not touching the solution. This is to prevent splash of the solution onto the litmus paper. Hang a piece of dampish 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 method in the Flinn Chemical compile / Reference Manual, suggested disposal method 11 (procedure B). See t he appendix.DiscussionIn your laboratory discussion embarrass 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 agree with this fact.3. Refer to a table of standard reduction potentials to find the values 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 F e3+ before the test for bromide by oxidation with MnO4- is done.5. Write 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 contact with the cotton or the solution?