| SAFETY NOTES: There are several strong acids and bases used in this lab. Use great care when handling them and wash hands immediately if you are splashed. |
| Part 1: Reactions of Cations with NaOH and NH3 | Each student should work independently for this lab. |
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Obtain a well plate from the front counter. Make sure it is clean and dry. |
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In two wells each, place 10 drops of each of the cations except for Na+. (All Na+ salts are soluble so we know that they will not react) |
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Use a wax pencil to label the contents of each well to avoid confusion. |
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To one of each of the two cation wells add 1 drop of 6M NaOH. Tap the plate gently to mix and carefully record observations of each cation. Now add 10 more drops of 6M NaOH to the same wells. Tap the plate gently to mix and carefully record observations of each cation. |
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Now add 10 drops of NH3 to each of the remaining cation wells. Tap the plate gently to mix and carefully record observations of each cation. |
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Discard the used solutions in the well plate in the designated waste container and rinse well. Remove any excess water by shaking or kimwipes. |
| Part 2: A Stability Sequence | |
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Combine 1 mL of AgNO3 and 1 mL of NaOH in a small test tube. Make and record your observations. |
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Centrifuge and discard the supernatent. Record all of your observations. |
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Add several eyedroppers full of Aqueous NaCl solution to the test tube and mix well. Record all of your observations. |
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Centrifuge and discard the supernatent. Record all of your observations. |
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Add NH3(aq) until the solid dissolves. Record all of your observations. |
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Add NaI until a reaction is seen. Record all of your observations. |
| Part 3: Anion Precipitation Reactions | |
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Place 10 drops of Ag+ into each of four wells on your well plate. Place 10 drops of Pb2+ into each of four wells on your well plate. |
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Add 1 drop of Cl- to one Ag+ well and one Pb2+ well. Record your observations. Add add an additional 10 drops of Cl- to the same Ag+ and Pb2+ wells. Record any changes. Repeat the above process for the remaining 3 anions (I-, SO42-, and NO3-). |
| Part 4: Sodium Ions | |
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Place a small amount of NaNO3 solution on a watch glass. Vaporize the NaNO3 under a Bunsen Burner in the hood. An intense Yellow flame confirms the presence of Sodium. See Video Example |
| Part 5: Nitrate Ions | |
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Place 20 drops of aqueous NaNO3 in a test tube. Note: If this was an unknown you would need to remove any Iodide from the sample first by precipitating it out using several drops of saturated Ag2SO4. Otherwise you would get a false positive. |
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Slowly and Very Carefully add 20 Drops of Concentrated Sulfuric Acid. |
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Now add ~ 5 drops of Iron II Sulfate heptahydrate by allowing the drops to roll gently down the inside of the test tube. DO NOT MIX! The formation of a smokey brown ring at the solution interface confirms the presence of Nitrate ion. |
| Part 6: The Unknown | |
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Collect ~ 10 mL of one of the unknowns provided from the front counter. Record the Code of the Unknown in your Notebook. Using the same tests and your recorded observations from above, determine the identity of the cation(s) and anion(s) present in your unknown. |
