Aluminium, sodium chloride and graphite are all crystalline solids - Leaving Cert Chemistry - Question 1 - 2007
Question 1
Aluminium, sodium chloride and graphite are all crystalline solids.
For each of these substances, name the type of crystal formed.
Explain clearly, in terms of bond... show full transcript
Worked Solution & Example Answer:Aluminium, sodium chloride and graphite are all crystalline solids - Leaving Cert Chemistry - Question 1 - 2007
Step 1
For aluminium, name the type of crystal formed.
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Answer
Aluminium forms a metallic crystal. This type of solid is characterized by a lattice of positively charged metal ions surrounded by a sea of delocalized electrons, which can move freely.
Step 2
For sodium chloride, name the type of crystal formed.
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Answer
Sodium chloride forms an ionic crystal. In this structure, sodium ions and chloride ions are arranged in a regular lattice, held together by strong electrostatic forces of attraction between the oppositely charged ions.
Step 3
For graphite, name the type of crystal formed.
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Answer
Graphite forms a covalent macromolecular crystal. This structure consists of layers of carbon atoms arranged in a hexagonal lattice, joined by covalent bonds within the layers.
Step 4
(i) aluminium is a good conductor of electricity.
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Aluminium is a good conductor of electricity because it has outer (valence, highest energy) electrons that are delocalised, forming a 'cloud' of electrons that are free to move when a potential difference is applied. This movement of electrons allows electric current to flow easily.
Step 5
(ii) sodium chloride is soluble in water.
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Sodium chloride is soluble in water due to the attraction between the ions in sodium chloride and polar water molecules. When sodium chloride is added to water, the positive sodium ions are attracted to the negative ends of the water molecules, while the negative chloride ions are attracted to the positive ends of the water molecules. This interaction allows the ions to become hydrated and disperse throughout the solution.
Step 6
(iii) graphite is soft and slippery.
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Answer
Graphite is soft and slippery because the forces between the layers of carbon atoms are weak (Van der Waals forces). These weak interactions allow the layers to slide over one another easily, resulting in the material's lubricating properties.
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