Halide Ions

Data Analysis

Obtain a kit of unknown solutions from your teacher -- they are numbered from 1 to 4. Identify which halide ion is in what Beral pipet but you have to perform this task in as few experiments as possible. An experiment is considered to be any time you combine drops from an unknown bottle with drops from a reagent bottle. Record each experiment you do.

Example: Unknown 1 + AgNO₃ --> Results?

Use a strategy, think about your plan. Remember, the fewer experiments, the better.

Go to Top

You will mix solutions together, two at a time, on an acetate sheet and record any evidence of reaction. After completing this experiment, you should be able to identify these halogen ions: F^-, Cl^-, Br^-, and I^-.

Go to Top

1. Place your acetate sheet on top of the data table above (the large dark dot in the center of each box provides contrast against which to view light colored reaction products). Use a paper clip to secure it in place. Put one drop each of NaF, NaCl, KBr, and KI in column two of your data sheet in the appropriate square. Add one drop of Ca(NO₃)₂ to each square so that it mixes with the drop you have already placed in that square. Observe and record any evidence of change on data table2 in the appropriate square.
2. Using the third column on your data table as a backdrop, add one drop of AgNO₃ to one drop of NaF, NaCl, KBr, and KI, as indicated. Observe and record any reactions on your second data table.
3. Using the fourth column on your data table as a backdrop, add one drop of AgNO₃ to one drop of NaF, NaCl, KBr, and KI, as indicated. Add three drops of NH₃ to each puddle formed, and mix thoroughly with a toothpick. Observe and record any reactions on your second data table.
4. Using the fifth column on your data table as a backdrop, add one drop of AgNO₃ to one drop of NaF, NaCl, KBr, and KI, as indicated. Add three drops of Na₂S₂O₃ to each puddle formed, and mix thoroughly with a toothpick. Observe and record any reactions on your second data table.
5. Use the sixth column on your data table as a backdrop to mix one drop of starch solution to one drop of NaF, NaCl, KBr, and KI. Observe and record any evidence of change on your second data table in the appropriate square. Add one drop of NaOCl to each of these puddles. Observe and record any evidence of change on your second data table in the appropriate square.
6. Clean off your equipment and wipe up your lab table thoroughly when you are finished with this experiment.

Go to Top

1. Name the four halide ions you worked with in this experiment.
2. Describe a method you can use to confirm the presence of each of these ions in solution.

Go to Top

• Do not spill the NaF solution on one's hands.
• NaF must be washed with soap immediately after use of NaF.
• Do not mix bleach and ammonia.
• Use adequate ventilation.

Go to Top

1. Fluoride, chloride, bromide, and iodide.
2. 1. Fluoride forms insoluble calcium fluoride.
   2. Chloride forms insoluble silver chloride that dissolves in ammonia.
   3. Bromide forms yellowish silver bromide that dissolves partly in ammonia but completely in sodium thiosulfate.
   4. Iodide forms yellow silver iodide that does not dissolve in either ammonia or sodium thiosulfate.

Go to Top

• 2 kits of Beral pipets containing the 10 solutions:
  • Reagent Kit:
    • 0.5M Ca(NO₃)₂ (8.2 g/ 100 mL)
    • 0.1M AgNO₃ (1.7 g/ 100 mL)
    • 4M NH₃ (26.7 mL concentrated ammonia/ 100 mL)
    • 0.2M Na₂S₂O₃ (5 g/ 100 mL)
    • 5% NaOCl (commercial bleach)
    • 3% starch solution (heat 100 mL of distilled water to boiling on a water bath; spray in starch spray from a laundry spray can, in bursts, with continuous stirring, until the solution takes on a bluish grey hue)
  • Halide Kit:
    • 0.1M NaF (0.4 g/ 100 mL)
    • 0.1M NaCl (0.6 g/ 100 mL)
    • 0.2M KBr (2.4 g/100 mL)
    • 0.2M KI (3.3 g/ 100 mL)
• 1 acetate sheet
• 1 data table
• unknown solutions

Go to Top