As pure elements, all of the halogens are diatomic molecular species. Their melting points are: F2, 85 K, Cl2, 239 K, Br2, 332 K, and I2, 457 K. Using the Periodic Table, predict as best you can the molecular 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.

At₂, solid

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 minus, B minus, and C minus ions, all of which are colorless. When a solution of C is mixed with one containing B minus ions, the color changes from red to yellow.

Which species is more active?

Hint:

For X₂ + 2 Y ^{1 minus} ---> Y₂ + 2 X ^{1 minus}

If a reaction occurs, X is more active than Y.

If a reaction does not occur, Y is more active than X.

• B
• C

C

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 minus, B minus, and C minus ions, all of which are colorless.

When a solution of C is mixed with one containing B minus ions, the color changes from red to yellow.

When a solution of C is mixed with one containing A minus ions, the color remains red.

Is C more active than A? _____________

Hint:

For X₂ + 2 Y ^{1 minus} ---> Y₂ + 2 X ^{1 minus}

If a reaction occurs, X is more active than Y.

If a reaction does not occur, Y is more active than X.

• Yes
• No

No

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 minus, B minus, and C minus ions, all of which are colorless.

When a solution of C is mixed with one containing B minus ions, the color changes from red to yellow.

When a solution of C is mixed with one containing A minus ions, the color remains red.

Is C more active than B? _____________

Hint:

For X₂ + 2 Y ^{1 minus} ---> Y₂ + 2 X ^{1 minus}

If a reaction occurs, X is more active than Y.

If a reaction does not occur, Y is more active than X.

• No
• Yes

Yes

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 minus, B minus, and C minus ions, all of which are colorless.

When a solution of C is mixed with one containing B minus ions, the color changes from red to yellow.

When a solution of C is mixed with one containing A minus ions, the color remains red.

Arrange A, B, and C in order of increasing activity. (1 is least active; 3 is most active)

Hint:

For X₂ + 2 Y ^{1 minus} ---> Y₂ + 2 X ^{1 minus}

If a reaction occurs, X is more active than Y.

If a reaction does not occur, Y is more active than X.

A - 3

B - 1

C - 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 minus, B minus, and C minus ions, all of which are colorless.

You are given an unknown, colorless, solution that contains one of the following salts: N a A, N a B, N a C. In solution, each salt dissociates completely into the Na+ ion and the anion A minus, B minus, or C minus. The N a + ion is effectively inert. You are given the availability of solutions of A, B, and C, develop a simple procedure for identifying the salt that is present in your unknown.

Hint:

For X₂ + 2 Y ^{1 minus} ---> Y₂ + 2 X ^{1 minus}

If a reaction occurs, X is more active than Y.

If a reaction does not occur, Y is more active than X.

React your unknown with A, B and C respectively. If a reaction occurs, your unknown is less active than what you reacted it with.

Instructor use only. 5% = 3.5