4.4.2 - Laboratory Activity : Studying the reaction of halogens with iron wool

Laboratory Activity 4.4.2: Studying the reaction of halogens with iron wool.

Aim: To study the reaction between halogen with iron.
Problem statement: How do chlorine, bromine and iodine react with iron?
Hypothesis: Reactivity decreases for the reaction between halogen and water when going down Group 17.
Variable:

	»	Fixed variable : Iron
	»	Manipulated variable : Type of halogen
	»	Responding variable : Reactivity of reaction

Material: » Chlorine gas » Bromine solution » Iodine crystals » Potassium manganate (VII) » Sodium hydroxide solution » Iron

Apparatus: » Delivery tube » Rubber stopper » Bunsen burner » Test tube » Conical flask » Thistle funnel » Filter funnel » Beaker » Combustion tube » Retort stand and clamp

Procedure:

	►	The animation below shows the procedures and observation of the experiment.
	►	(A) With chlorine 1. Chlorine gas is passed over hot iron wool in the combustion tube. 2. All observation are recorded.
	►	(B) With bromine 1. The bromine liquid in the boiling tube is warmed up and the vapours are passed through hot iron wool. 2. All observation are recorded.
	►	(C) With iodine 1. The iodine crystals are heated in the boiling tube and the vapours are passed through hot iron wool. 2. All observation are recorded.

Results:

►

Halogen Observation Chlorine Iron wool burns brightly and forms a brown solid when cooled. Bromine Iron wool glows brightly and forms a brown solid when cooled. Iodine Iron wool glows slowly with a dull glow and forms a brown solid when cooled.

Discussion:

	►	Chlorine, bromine and iodine react with iron to form iron (III) halide.
	►	Chlorine react vigorously with iron to produce iron (III) chloride. ○ $\mathrm{2Fe(s)\; +}{\mathrm{3Cl}}_2\mathrm{(g)}\to {\mathrm{2FeCl}}_3\mathrm{(s)}$
	►	Bromine reacts less vigorously with iron to produce iron (III) bromide. ○ $\mathrm{2Fe(s)\; +}{\mathrm{3Br}}_2\mathrm{(g)}\to {\mathrm{2FeBr}}_3\mathrm{(s)}$
	►	Iodine reacts slowly with iron to produce iron (III) iodide. ○ $\mathrm{2Fe(s)\; +}{\mathrm{3I}}_2\mathrm{(g)}\to {\mathrm{2FeI}}_3\mathrm{(s)}$
	►	The reactivity of the halogens with iron decreases when going down Group 17.

Conclusion:

	►	Halogens react with iron.
	►	The reactivity increases down the Group 17.
	►	The hypothesis is accepted.

↶ 4.4 Group 17 Elements

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