The halogens – properties and reactions quiz

1. Which of the following elements is not a halogen?

a) Fluorine
b) Chlorine
c) Oxygen
d) Bromine

2. Which statement correctly describes the physical states of the first four halogens at room temperature?

a) Fluorine and chlorine are gases, bromine is a liquid and iodine is a solid.
b) Fluorine is a liquid, chlorine and bromine are gases and iodine is a solid.
c) All four are gases at room temperature.
d) Fluorine and chlorine are liquids, bromine and iodine are solids.

3. What is the general trend in colour of the halogens as you go down group 7?

a) They become paler in colour down the group.
b) They become darker and more intense in colour down the group.
c) They all have exactly the same colour.
d) The colour alternates between colourless and coloured down the group.

4. In their elemental form the halogens exist as molecules, for example Cl₂, Br₂ and I₂.

5. Why do the melting and boiling points of the halogens increase as you go down group 7?

a) Because the covalent bonds within the molecules become stronger down the group.
b) Because the atoms become more electronegative down the group.
c) Because the halogens become more reactive down the group.
d) Because larger molecules have stronger van der Waals (London dispersion) forces between their molecules.

6. The halogens act as agents because they gain electrons in redox reactions, and this ability decreases down the group.

7. Which of the following correctly shows the trend in electronegativity for the halogens?

a) F > Cl > Br > I
b) I > Br > Cl > F
c) Cl > F > Br > I
d) Br > I > Cl > F

8. When chlorine dissolves in water it forms a mixture of hydrochloric acid and (I) acid.

9. Which statement about the solubility of the halogens is correct?

a) They are very soluble in water but insoluble in organic solvents.
b) They are insoluble in both water and organic solvents.
c) They are only slightly soluble in water but dissolve readily in non-polar organic solvents such as cyclohexane.
d) They dissolve equally well in water and in organic solvents.

10. Which equation correctly represents the reaction of chlorine with water?

a) Cl₂ + H₂O → 2HClO
b) Cl₂ + H₂O ⇌ HCl + HClO
c) Cl₂ + 2H₂O → 2HCl + O₂
d) 2Cl^- + H₂O → Cl₂ + 2OH^-

11. Which observation best describes what happens when solid iodine is added to an aqueous potassium iodide solution?

a) A colourless solution forms as iodine dissolves completely.
b) A green solution of iodine forms immediately.
c) A white precipitate of silver iodide forms.
d) A brown solution forms containing triiodide ions, I₃^-.

12. In halogen displacement reactions, a more reactive halogen will a less reactive halogen from its halide solution.

13. Which of the following combinations would you expect to show a displacement reaction?

a) Chlorine water added to potassium iodide solution.
b) Iodine solution added to potassium chloride solution.
c) Bromine water added to potassium chloride solution.
d) Iodine solution added to potassium bromide solution.

14. What is the general trend in the reactivity of the halogens with hydrogen gas, H₂?

a) All halogens react explosively with hydrogen under the same conditions.
b) Reactivity increases down the group, with iodine being the most reactive.
c) Reactivity decreases down the group; fluorine reacts most vigorously, iodine least.
d) Only chlorine reacts with hydrogen; the others do not react at all.

15. Fluorine has the highest of all the elements, meaning it attracts electrons in a covalent bond more strongly than any other element.

16. In a typical school laboratory, which halogen is usually considered the safest to handle (under suitable precautions)?

a) Fluorine gas
b) Chlorine gas
c) Liquid bromine
d) Solid iodine

17. The characteristic “swimming baths” smell is mainly caused by:

a) Pure chlorine gas escaping from the pool.
b) Chloramines formed when chlorine reacts with sweat and urine.
c) Ozone produced by UV lamps.
d) Sodium chloride in the pool water.

18. Why does the oxidising power of the halogens decrease down group 7?

a) Because the nuclear charge decreases down the group.
b) Because the number of electrons in the outer shell decreases down the group.
c) Because the halogens become smaller and less shielded down the group.
d) Because increased atomic radius and shielding make it harder for the atom to gain an electron.

19. When bromine reacts with water it forms a mixture of hydrobromic acid and (I) acid.

20. When iodine is dissolved in an organic solvent such as cyclohexane, what colour is observed?

a) Pale green
b) Orange-brown
c) Purple
d) Colourless