Question

Section Name Experiment 12 Advance Study Assignment: The Alkaline Earths and the Halogens I. As pure clements, all of the halogens are diatomic molecular species, Their melting points are: F,, 54 K: Br 266 K; and I, 387 K. Using the Periodic Table, predict as best you can the molecular Cl., 172 1 formula of elemental astatine, At, the only radioactive element in this family. Also predict whether it will be a solid, liquid, or gas at rOom temperature. Elemental fornmula: Phase at room temperature 2. Substances A, B, and C, can all act as oxidizing agents. In solution, A, is green, B, is yellow, and C, is red. In the reactions in which they participate, they are reduced to A , B ,and C ions, all of which are colorless. When a solution fC, is mixed with one containing B ions, the color changes from red to yellow Which species is oxidized? Which is reduced? When a solution of C, is mixed with one containing A" ions, the color remains red. Is C, a hetter oxidizing agent than A,? Is C, a better oxidizing agent than B. Arrange A, B and C, in order of increasing strength as an oxidizing agent. strongest oxidizing agent weakest oxidizing agent fcontinued on following page) 88 The Alka line Earths and the Halogens-Two Familles Experiment 12 the Penodic Table 3 You are given a colorless unknown solution that contains one of the following salts: NaA, NaB, NaC. In solution, cach salt dissociates completely into the Na" ion and the anion A,B", or C", whose properties are given in Problem 2. The Na" ion is effectively inert. Given the availability of solutions of A, B and C, develop a simple procedure for identifying the salt that present in your unknown.

Answer 1

1) Element formula of astatine is At₂ because is an halide or an 17th group element. These elements reacts with itself forming diatomic molecules like: F₂, Cl₂, etc... .

At₂ is solid at room temperature because boiling points increases according we move descendent into 17th group.

2) C₂ oxidizes B^- to B because color changes from red to yellow and C₂ is reduced because it takes electrons from B^-

C₂ is worse oxidant than A₂ because color does not change and A2 prefers being reduced than C2

C₂ is better oxidant than B₂ because the spontaneous reactions is:

C22B 20+B

and its color changes from red to yellow

3) To identify what compound is present we have to make color development from a colorless solution. A^- is less stable than C^- and probably reduces to C₂ to develop a red solution