Question

A. Physical State of Halogens at Room Temperature 1. Samples of the elemental halogens are provided. Describe them: Chlorine Description green gas. orange llauid black line stores (alonost clystal-like) Bromine lodine NOTE: These are all reactive elements. Do not touch them or breath their vapors 2. The halogens are unique as a group because chlorine is a gas, bromine is a liquid and lodine is a solid. Compare the Lewis structures of the halogens (Pre-lab). Can you suggest a reason for the different physical states from the Lewis structures? Explain. Tre lewis Stud ies oll lock the Serre however because they are in different Periods in the pitcn extra stell of electrons is cooke from top to bottom, wrich could explain the diffeent states 3. Can you suggest another reason why chlorine is a gas, bromine is a liquid, and iodine is a solid? The force of attraction between the roleculles increases from botom to top on the periodic table 4. The chlorine that you will be using in this lab is prepared fresh for each lab period by mixing chlorine bleach and concentrated HCI. Chlorine gas forms from this reaction. Why do you suppose that the mixture must be prepared fresh for each lab period? 5. You can simply look at the mixture of chlorine bleach and concentrated HCl and determine if there is chlorine gas present. a. What would the mixture look like if chlorine gas were present? b. What would the mixture look like if chlorine gas were not present? 12-3

Answer 1

3. Chlorine is a gas. Bromine is a liquid and iodine is a solid. The force of attraction between the molecules increases from the top to bottom of the group. The molecules of each substance is a solid liquid or gas depends on the balance between the Kinetic energies of the molecules and there intermolecular attractions.

In chlorine the electrons have little chance in wander to one side of the molecule. So the London dispersion is weak. As we move from top to bottom the electrons are further from the nuclei so the electron clouds can more easily destort the London dispersion forces become stronger.

4. Bleach solution becomes unstable rapidly hence it needs to be freshly prepared daily or changed on becoming dirty. Chlorine bleach can be corrosive. chlorine solution gradually loose strength because of this it must be prepared freshly.

5. a. If chlorine gas is present, it has the pungent irritating odor and it appears to be yellow green in colour. But it is toxic to human beings.

b. If it is not present, not so much irritating smell