Aluminium is a highly reactive metal, and when it reacts with halogens such as chlorine, bromine, and iodine, solid aluminium halides are formed. These reactions highlight the reactivity of non-metals from Group 17 when they interact with metals.
It is important to note that these reactions can be hazardous, so it is recommended to carry out the experiments in a fume cupboard to ensure safety. Educators who are conducting this demo for the first time should practice beforehand to familiarize themselves with the procedure.
Each experiment is relatively quick, taking around five minutes to complete. Students will observe the formation of solid aluminium halides during the interactions with halogens, providing a hands-on demonstration of chemical reactions involving aluminium.
Safety Precautions
Recommended Safety Gear for the Experiment
- Protective eyewear (goggles)
- Chemical-resistant gloves
- Access to a fume cupboard
- Mortar and pestle
- Heat-resistant mat
- Watch glasses
- Reduction tube
- Test tubes
- Test tube rack
- Teat pipette
- Filter paper
- Spatula or wooden splint
- Bosses, clamps, and stands
Materials for the Reactions
- Aluminium foil
- Aluminium powder
- Liquid bromine
- Solid iodine
- Silver nitrate solution
- Deionised water
- Chlorine generator
- Sodium chlorate(I) solution
- Hydrochloric acid
Chlorine Gas Reaction with Aluminium
Source: Royal Society of Chemistry
Step-by-step guide for generating chlorine gas to react with aluminium
Experimental Procedure
Reaction with Chlorine Gas
- Safely set up the chlorine generator within a fume cupboard.
- Insert aluminium foil into the reduction tube connected to the generator.
- Produce a stream of chlorine gas by combining hydrochloric acid with sodium chlorate(I) solution, then heat the aluminium foil to initiate the reaction.
- Allow the reaction to occur, then examine the resulting solution.
- Test the solution for acidity and chloride ions.
Reaction with Bromine
- Immerse aluminium foil in liquid bromine to observe the formation of aluminium bromide.
- Collect the product and test the solution for acidity and bromide ions.
Reaction with Iodine
When working with iodine and aluminium, it is crucial to follow proper safety measures.
- Weigh, mix, and monitor the reaction between iodine and aluminium powder.
- Test the resultant solution for acidity and iodide ions.
Concluding Remarks
These reactions can serve as captivating demonstrations, illustrating the reactivity between non-metals and metals.
They also showcase the surprising reactivity of aluminium and stress the importance of conducting fair reactivity comparisons.
It is advisable for teachers to perform the iodine and aluminium reaction outdoors due to the release of iodine vapour.
Residue disposal should only be carried out in a fume cupboard.
Further Resources
This resource is part of the Practical Chemistry project by the Nuffield Foundation and the Royal Society of Chemistry.
Practical Chemistry provides support for activities in Physics and Biology.
Aluminium Reactivity Overview
Aluminium, a lustrous white metal, forms aluminium(III) oxide upon exposure to air. It reacts with halogens to yield various aluminium halides.
Reactivity with Air and Water
Aluminium can react with air or water if its oxide layer is compromised.
When exposed to air, aluminium can react to form a thin layer of aluminium oxide on its surface, which can protect it from further corrosion. However, if this oxide layer is damaged or removed, the metal can react with oxygen in the air to form aluminium oxide. Similarly, when in contact with water, aluminium can react to form aluminium hydroxide and hydrogen gas. It is important to properly store and handle aluminium to prevent its reactivity with air and water.
Reactions with Halogens
Aluminium readily reacts with halogens to form aluminium halides. The reaction with fluorine is highly exothermic and typically requires a catalyst such as iron or copper to initiate the reaction. With chlorine, aluminium forms aluminium chloride, a white crystalline solid. Bromine reacts with aluminium to produce aluminium bromide, which is a yellow-green solid. Finally, aluminium reacts with iodine to form aluminium iodide, a dark-red solid. These reactions with halogens showcase the reactivity of aluminium towards halogens and the formation of different aluminium halides depending on the halogen used.
Aluminium also has a high strength-to-weight ratio, making it ideal for use in various applications such as construction, transportation, and packaging.
When exposed to air, aluminium forms a thin layer of oxide on its surface, which provides protection against further oxidation.
Aluminium is a good reflector of both visible light and heat, making it a popular choice for solar reflectors and heat exchangers.
In addition to its reactivity with acids, aluminium can also react with alkalis to form aluminates, such as sodium aluminate.
Aluminium is non-magnetic and non-toxic, making it a safe and versatile material for a wide range of applications.
Overall, the unique combination of properties and reactivity of aluminium make it a valuable material in various industries and everyday products.
Interactions with Hydrochloric Acid
When multiple metals are combined and treated with hydrochloric acid, each metal reacts individually. For example, when HCl is added to a mixture of aluminum and iron shavings, the reactions proceed as follows:
Fe + 2HCl = FeCl₂ + H₂↑
2Al + 6HCl = 2AlCl₃ + 3H₂↑
Due to the weak oxidizing nature of diluted hydrochloric acid, iron is only reduced to a +2 oxidation state.
Aluminium Chloride Formation
Almost all reactions involving hydrochloric acid and aluminium (or its compounds) lead to the production of aluminum chloride (AlCl₃). This salt dissolves effectively in organic solvents (such as nitrobenzene, dichloroethane, and acetone) and water. In aqueous solutions, the hydrolysis of AlCl₃ can be observed, as this salt is a result of the reaction between the strong acid HCl and the weak base Al(OH)₃.
AlCl₃ serves as a catalyst in organic synthesis processes, including isomerization of paraffins, initiation of alkylation reactions, acylation, and oil fractionation. Aluminum chloride hexahydrate AlCl₃・6H₂O is utilized for timber treatment, wastewater purification, and manufacturing antiperspirants.
The reaction between aluminum and hydrochloric acid solution can be employed as a laboratory method to generate hydrogen gas (although metallic zinc is more commonly used for this purpose).
Click here to discover more about aluminium and its characteristics.