2b-Group 7 (halogens) – chlorine, bromine and iodine

Question 1

Question: What are the halogens in Group 7 that you need to know?

Answer 1

Answer: Fluorine (F), Chlorine (Cl), Bromine (Br), and Iodine (I).

Question 2

Question: What are the physical states and colors of the halogens at room temperature?

Answer 2

Fluorine (F₂): Pale yellow gas

Chlorine (Cl₂): Green gas

Bromine (Br₂): Red-brown liquid

Iodine (I₂): Dark grey solid (sublimes to a purple vapor)

Question 3

Question: How does the reactivity of Group 7 elements change down the group?

Answer 3

: Reactivity decreases down the group because the outer electron shell is farther from the nucleus, making it harder to gain an electron.

Question 4

What are the trends in boiling and melting points in Group 7?Answer: Boiling and melting points increase down the group because intermolecular forces become stronger as molecules get larger.

Answer 4

Answer: Boiling and melting points increase down the group because intermolecular forces become stronger as molecules get larger.

Question 5

What happens when halogens react with metals?

Answer 5

Halogens react with metals to form metal halides (ionic compounds). Example:

Sodium + Chlorine → Sodium Chloride2Na (s) + Cl₂ (g) → 2NaCl (s)

Question 6

Question: What happens when halogens react with hydrogen?

Answer 6

Answer: Halogens react with hydrogen to form hydrogen halides, which dissolve in water to form acidic solutions. Example:

Hydrogen + Chlorine → Hydrogen ChlorideH₂ (g) + Cl₂ (g) → 2HCl (g)

Question 7

Question: What is a displacement reaction involving halogens?

Answer 7

Answer: A more reactive halogen will displace a less reactive halogen from its compound in solution. Example:

Chlorine + Potassium Bromide → Potassium Chloride + BromineCl₂ (g) + 2KBr (aq) → 2KCl (aq) + Br₂ (aq)

Question 8

Question: How does the color change in a displacement reaction indicate reactivity?

Answer 8

Answer: The color of the displaced halogen appears in the solution, indicating that a reaction has occurred. Example:

Chlorine displacing bromine turns the solution orange.

Chlorine displacing iodine turns the solution brown.

Question 9

Practical: Investigating Displacement Reactions of Halogens
Method:

Answer 9

Add chlorine, bromine, or iodine solutions to test tubes containing potassium chloride, potassium bromide, and potassium iodide solutions.

Observe any color changes indicating displacement.

Question 10

Practical: Investigating Displacement Reactions of Halogens
Results and conclusion

Answer 10

Results:

Chlorine displaces bromine and iodine (orange and brown solutions appear).

Bromine displaces iodine (brown solution appears).

Iodine does not displace anything (no reaction).

Conclusion:

Reactivity decreases down Group 7.