Group VII Properties (Cambridge O Level Chemistry)

Three of the halogens in Group VII are listed below.

A radioactive isotope of iodine, , is used to treat cancer.

Extended Only

Fluorine, the most reactive halogen, forms compounds with the other halogens. It forms two compounds with bromine.
Deduce their formulae from the following information.

Table 1 shows some properties of some of the halogens.

                                                                  Table 1Use the information in Table 1 to suggest:

• the colour of astatine ______________
• the boiling point of bromine ____________
• the state of iodine at 190 °C _______________

Aqueous chlorine reacts with aqueous potassium bromide as shown.

                                              Cl₂ + 2KBr → Br₂ + 2KCl

Name the salt formed in this reaction.

Explain why aqueous bromine does not react with aqueous potassium chloride.

Complete the dot-and-cross diagram in Figure 1 of a molecule of chlorine.
Show outer shell electrons only.

Figure 1

The halogens are a collection of diatomic non-metals in Group VII.

The halogens react with other non-metals to form covalent compounds.
Draw a diagram which shows the arrangement of the valency electrons in one molecule of the covalent compound arsenic trifluoride.
The electron distribution of an arsenic atom is 2 + 8 + 18 + 5.
Use x to represent an electron from an arsenic atom.
Use o to represent an electron from a fluorine atom.

Photochromic glass is used in sunglasses. In bright light, the glass darkens reducing the amount of light reaching the eye. When the light is less bright, the glass becomes colourless increasing the amount of light reaching the eye.
Photochromic glass contains very small amounts of the halides silver(I) chloride and copper(I) chloride.
The reaction between these two chlorides is photochemical.

AgCl	+	CuCl		Ag	+	CuCl2
colourless		colourless		black		colourless

How does photochromic glass work?

Three of the halogens in Group VII are:

chlorine
bromine
iodine

Describe how you could distinguish between aqueous potassium bromide and aqueous potassium iodide.

Test ....................

Result with bromide ............................................................

Result with iodide ............................................................

0.015 moles of iodine react with 0.045 moles of chlorine to form 0.030 moles of a single product.

Complete the equation.

I₂ + ............ Cl₂ → ................................

Traces of chlorine can be separated from bromine vapour by diffusion.

Which gas would diffuse the faster and why?