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Structure for SQA National 5 Chemistry

Structure

This page covers the following topics:

1. Ionic compounds

Ionic compounds form giant regular crystalline ionic lattices, held together by the strong electrostatic forces of attraction between the oppositely charged ions. Ionic lattices may be presented in 2D or 3D by including formulae of the ions or just the charge of them. Sodium chloride (NaCl) is a common example an ionic lattice and is sometimes called rock salt or table salt.

Ionic bonding is stronger than intermolecular forces in other solids. Therefore, compounds that break ionic bonds when they melt or boil, require much more energy, which results in higher melting or boiling points. In contrast, materials that only break weak intermolecular interactions while melting or boiling, require less energy and have lower melting/boiling points.

If ions from an ionic compound are free to move, a compound can conduct electricity. This is true for molten ionic compounds and ionic compoundsโ€™ solutions. Solid ionic compounds do not conduct electricity as their ions cannot move.

Ionic compounds

1

Which of the following conduct(s) electricity?

โ‹… molten ice
โ‹… molten table salt
โ‹… rock salt and water solution
โ‹… solid silver iodide precipitate
โ‹… iron oxide powder

If ions from an ionic compound are free to move, a compound can conduct electricity. This is true for molten ionic compounds and ionic compoundsโ€™ solutions. Solid ionic compounds do not conduct electricity as their ions cannot move.

โ‹… molten ice: no charged particles to transfer electricity โ†’ no
โ‹… molten table salt: ions that are free to move โ†’ yes
โ‹… rock salt and water solution: ions that are free to move โ†’ yes
โ‹… solid silver iodide precipitate: ions that are not free to move โ†’ no
โ‹… iron oxide powder: ions that are not free to move โ†’ no

molten table salt, rock salt and water solution

Which of the following conduct(s) electricity? 

โ‹… molten ice 
โ‹… molten table salt 
โ‹… rock salt and water solution 
โ‹… solid silver iodide precipitate 
โ‹… iron oxide powder

2

Why does pure lithium chloride only conduct electricity above its melting point?

If ions from an ionic compound are free to move, a compound can conduct electricity. This is true for molten ionic compounds and ionic compoundsโ€™ solutions. Solid ionic compounds do not conduct electricity as their ions cannot move. When lithium chloride reaches its melting point it melts, its ions are free to move; and thus, it conducts electricity.

When lithium chloride reaches its melting point it melts, its ions are free to move; and thus, it conducts electricity.

Why does pure lithium chloride only conduct electricity above its melting point?

3

Which of the following qualities apply to ionic lattices?

โ‹… regular structure
โ‹… low boiling points
โ‹… intermolecular forces
โ‹… covalent bonds
โ‹… high melting points
โ‹… electrostatic forces

Ionic compounds form giant regular crystalline ionic lattices, held together by the strong electrostatic forces of attraction between the oppositely charged ions. Compounds that break ionic bonds when they melt or boil, require much more energy, which results in higher melting or boiling points.

regular structure, high melting points, electrostatic forces

Which of the following qualities apply to ionic lattices? 

โ‹… regular structure 
โ‹… low boiling points 
โ‹… intermolecular forces 
โ‹… covalent bonds 
โ‹… high melting points 
โ‹… electrostatic forces

4

Draw a 2D sketch of a calcium oxide lattice.

Ionic compounds form giant crystalline ionic lattices, held together by the strong electrostatic forces of attraction between the oppositely charged ions. Ionic lattices may be presented in 2D or 3D by including formulae of the ions or just the charge of them.

image

Draw a 2D sketch of a calcium oxide lattice.

5

Lithium chloride is dissolved in water, does this solution conduct electricity? Explain your answer.

If ions from an ionic compound are free to move, a compound can conduct electricity. This is true for molten ionic compounds and ionic compoundsโ€™ solutions.

Yes, the ions are free to move.

Lithium chloride is dissolved in water, does this solution conduct electricity? Explain your answer.

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