Wednesday, 14 January 2015

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.
2Fe(s) + 3Cl2(g) 2FeCl3(s)

Bromine reacts less vigorously with iron to produce iron (III) bromide.
2Fe(s) + 3Br2(g) 2FeBr3(s)

Iodine reacts slowly with iron to produce iron (III) iodide.
2Fe(s) + 3I2(g) 2FeI3(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.


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