Question

PART B The operations in this part will take place in the hood. To avoid traffic problems, plan ahead and work efficiently to occupy the hood for a minimal time. After making a set of test tube additions, step back to mix the tubes and allow others to have access to the materials. Clean and rinse the four-inch (small) and six-inch (medium) test tubes from your drawer. Use three of the four-inch tubes to observe the colors of the halogen molecules in hexane. Start by adding 10-12 drops of the chlorine-water solution from a dropper bottle to one tube. Add 10-12 drops of hexane to the same tube. To avoid continual opening and closing of the primary hexane reservoir, there will probably be a small flask or beaker to pour a small amount of hexane in and use as a source for the pipet droppers. Use synthetic wrap and your thumb or finger to cover the tube and shake it to mix the contents. After mixing, let the contents settle into an aqueous layer and a hexane layer. Since water is more dense, it will be the bottom layer. Use the data chart to record any colors apparent in the hexane and water layers. In separate tubes, repeat the process with bromine-water and hexane, then with iodine- water and hexane to complete the color reference chart. Keep the three tubes on hand for comparisons. In the reaction tests that follow, the colors in the hexane layer of your tests in the medium tubes will be compared to the reference colors in the small tubes to determine which molecular halogen is present and whether a reaction occurred. There are six reaction tests. Do two at a time so you can alternate accessing materials with other teams. Choose one of the halogen-water solutions and add 15-18 drops to each of two six-inch test tubes. Add 15-18 drops of hexane to each without mixing. Then, to one tube each, add 15-18 drops of the 0.1 M sodium salt solution of one of the other two halides. For example, to two test tubes with Cl, in water, add hexane to each then add 0.1 M NaBr to one tube and 0.1 M Nal to the other tube. Mix the contents by shaking vigorously, then record the colors in the hexane layers in the data chart. til each halogen has been tested with each halide. You do not need to test a halogen with itself, so you should end up performing a total of 6 combinations. See the data table given on the next page for help with the pairings. Once you are satisfied with your data, discard all solutions in the hexane waste collection bottle. Clean your glassware and work with your partner on a preliminary interpretation of your data. If some results seem inconsistent, check with the instructor to determine whether there are sufficient supplies of the solutions to allow repeating one or more tests.

Answer 1

Part 5.

i) Cl₂ + Br^- ---->

ii) Cl₂ + I^- ---->

iii) Br₂ + Cl^- ---->

iv) Br₂ + I^- ---->

v) I₂ + Cl^- ---->

vi) I₂ + Br^- ---->

Part 6.

The molecular halogen (Cl₂/Br₂/I₂) is present in the hexane layer because both of them are nonpolar.

The ionic halide (Cl^-/Br^-/I^-) is present in the water layer because both of them are polar.