Expt:Reacting elements with chlorine

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Introduction

Many elements react with chlorine. The ease with which the reaction takes place, the vigour of the reaction and the properties of the compounds made provide excellent evidence to help understanding about the periodic nature of the elements in the Periodic Table.

The comparison of the properties of oxides and chlorides of various elements widens and deepens the understanding that students gain from seeing only one set of compounds.

Apparatus and chemicals

• Fume cupboard
• Gas preparation apparatus:

• Side-arm flask 250 cm3
• Tap funnel and bung to fit flask
• Connecting tubing
• Reaction tubes, one for each reaction (see Experiment 14 for how to make a reaction tube)
• 1-hole bung and delivery tube to fit
• Clamp stand
• Boss head
• Clamp

For chlorine generation

• Concentrated hydrochloric acid, 14 cm3 5 mol dm-3 (Corrosive, Refer to CLEAPSS® Hazcard 47A) (see note 2)
• Potassium manganate(VII), 3g (Oxidising, Harmful, Danger to the environment Refer to CLEAPSS® Hazcard 81)
• Sodium thiosulfate solution 1 dm3, 40g dm-3 (Low hazard, Refer to CLEAPSS® Hazcard 96C) (see note 3)

The other elements

• Lithium (Highly flammable, corrosive, Refer to CLEAPSS® Hazcard 58) (see notes 4 and 5)
• Sodium (Highly flammable, corrosive, Refer to CLEAPSS® Hazcard 88)
• Potassium (Highly flammable, corrosive, Refer to CLEAPSS® Hazcard 76)
• Magnesium (Highly flammable, Refer to CLEAPSS® Hazcard 59A) (see note 6)
• Calcium (Highly flammable, Refer to CLEAPSS® Hazcard 59A)
• Aluminium foil (Low hazard, Refer to CLEAPSS® Hazcard 1)
• Carbon (Low hazard, Refer to CLEAPSS® Hazcard 21)
• Phosphorus Red (Highly flammable, Refer to CLEAPSS® Hazcard 73A)
• Sulfur (Low Hazard, Refer to CLEAPSS® Hazcard (96A)

Technical notes

1. It is recommended that these experiment are done by the demonstrator before demonstrating to pupils, in order to gain experience if they have not done it before.
2. A steady evolution of chlorine gas can be obtained by dripping concentrated hydrochloric acid onto solid potassium manganate(VII). Chlorine should be generated in small amounts at a time.
3. Sodium thiosulfate solution rapidly reduces chlorine gas to harmless chloride ions. Excess chlorine can be bubbled into small quantities of sodium thiosulfate solution in a beaker, as necessary.

The other elements

1. Group 1 metals are stored under oil; this can be removed by using tissue paper.
2. Cut pieces of Group 1 metals into cubes no bigger than 3mm.
3. For the other elements 0.1g is sufficient to see a spectacular reaction.

Procedure

Health & Safety

Wear eye protection at all times and work under the fume cupboard. Wear gloves at all times - chlorine gas will react with rings, etcetera.

Procedure

A. The apparatus is assembled in a fume cupboard, according to the diagram.

B. A reaction tube is clamped horizontally close to the bung end.

C. The tubes are used to connect the gas generator to the delivery tube in the bung.

D. A piece of the element is placed near the bottom of the test tube.

E. The bung is pushed gently into the reaction tube.

F. Start the chlorine gas generation by running hydrochloric acid onto the potassium manganate(VII) solid.

G. Heat the solid element using a Bunsen burner with a blue flame.

H. Add more hydrochloric acid slowly

I. Remove the Bunsen burner as the element catches fire

Reference

This experiment was written by Mike Thompson on behalf of the RSC