a. For each anion in today\'s experiment: Cl-, I-, PO4-3, SO4-2, use the solubil

Question

a. For each anion in today's experiment: Cl-, I-, PO4-3, SO4-2, use the solubility rules to determine if a precipitate SHOULD form when using the reagents in the procedure.

b. Why is emphasis placed on the use of distilled water in the procedure?

GENERAL TIPS You will be using the micro-scale equipment, including Micro-centrifuge tubes for test tubes. At the end of the period, you will empty the contents of any of the tubes into the waste crock, and put the disposable tubes in the waste can. Capillary tubes for stirring rods; used the closed end. Dispose of in the broken glass container Please note that some of the solutions (e.g. 0.20 M AgNO,) are available in droppers to minimize waste. These droppers typically have a narrower tip, and provide smaller sized drops or "micro-drops." Two micro-drops are equivalent to one drop. Micro-centrifuge test tube racks and well plates. Please DO NOT use acetone to clean the well plates 100-mL beaker mostly filled with deionized (DiI) water, and covered with aluminum foil and set on a hot plate, for the hot water bath. Set this up before you prepare your A solutions, so the water is hot when you need it. Heat the water to near boiling Use a pen to poke small holes in the aluminum foil cover. You will later use the lid of a micro- centrifuge tubes as a handle, when you place the tube in the hole of the foil to gently heat the contents of the tube. PART I: PREPARATION OF ANION SOLUTIONS You will be diluting the stock solutions of each of the knowns (0.5 M NaCI, KI, Na,PO, and Na SO,) and your two assigned unknowns. You will need six clean 10-cm (4") test tubes. For each of the six solutions: 1. Label the test tube (eg, NaCl, Unknown #2 ). You may also want to label a disposable pipet to be used with each solution. Add 10 drops of the stock solution (e.g. 0.5 M NacI). 2. Add 40 drops of DI water. Use a dedicated pipet to agitate the solution and mix thoroughly. You may leave this pipet in the test tube to be used for delivery later. Be careful not to cross-contaminate your solutions. 3. PART II: CONTROL REACTION 6 M HNO, +o.2 M AgNO, You will be following the same procedure for each of your six solutions. Do each step of the procedure to all the solutions side-by-side, so that you may compare the results. At the end of the lab, you will be able to identify which of the four known anions are in each of the unknown solutions. The unknowns may contain any or all of the known anions. For each of you six solutions: Add 5 drops of the solution to a new micro-centrifuge tube. Add 2 drops of 6 M HNO, Stir with the closed end of a clean capillary tube. 1. 14 QUALITATVE ANALSYSIS F ANIONS 167

Explanation / Answer

2) Distilled water is used because no ions can be present in the water used in the experiment. You are going to identify ions in samples so you cannot introduce ions to the experiment by using tape water, for example.

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