To identify a halide, you can react a solution with chlorine water in the presence of mineral oil. If the unknown halide is a
Choose...weaker/stronger
reducing agent than chlorine, the halide will be oxidized to
Choose...its elemental form/ its ionic form/ a solid
which would change the color of the
Choose...mineral oil/ aqueous
layer.

- Stronger reducing agent than Chlorine

- Oxidized to it's elemental form

- Change the colour of the aqueous layer.

Explanation:

Halides are electronegative elements in group seven of the Periodic table which have gained electrons to complete their electronic configuration.

They include F-, CL-, Br- and I-.

As you descend the group electro negativity decreases as the number of outermost shells increases. Hence F- is the most electronegative while I- is the least electronegative.

In terms of oxidising and reducing abilities amongst the halogens, since an oxidizing agent readily accepts electrons and is thereby reduced, oxidizing power decreases down the group.

For example, Fluorine being the strongest oxidising agent in the group readily accepts electrons from other members of the group and is reduced to the fluoride ion

F + e = F -

Therefore in terms of oxidizing abilities,

F > Cl > Br > I

Conversely, , as the oxidising power decreases down the group, the reducing powers increases

Therefore, in terms of reducing powers,

I > Br > Cl > F

In the test for halide ions using aqueous chlorine, since chlorine is a stronger oxidizing agent/weaker reducing agent than Bromine or iodine, it readily accepts their electrons forming the chloride ion.

Cl2 + 2 Br- = 2 Cl- + Br2

The bromide ion (assuming the unknown halide is bromide) being a stronger reducing agent/weaker oxidizing agent than Chlorine would readily lose it's electrons and get oxidized to it's elemental form changing the colour of the aqueous layer to brown.

That is : Br2- = Br2 + 2e

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