par 6.3 salts

• Scheikunde
• Middelbare school
• vwo
• Leerjaar 3

6.3 salts

- Some properties of salts

- The structure of salts at micro level

- Formation of ions

- What happens when a salt dissolves in water and when you evaporate a salt solution.

Metals do not conduct electricity in liquid phase

1. yes
2. no

Molecular substances conduct electricity in solid phase

1. yes
2. no

Al₂O₃ is a ...

1. metal
2. molecular substance
3. salt

Salts conducts in liquid phase

1. Yes
2. No

Properties of salts

• High melting- and boiling points, strong bond.
• No conductivity in solid state, conducts in liquid state. So there must be freely moving particles in liquid state, but not in solid state.

the name for the particles that can conduct electricity

1. atoms
2. molecules
3. ions

Formulas of salts

• metal ion with non-metal ion.
• Example : NaCl sodium chloride ( kitchen salt)
•                  sodium-ion (metal)
•                  chlorine-ion (non-metal) 

Na​1+​​

Cl​1−​​

forming of ions

• to conduct there have to be particles with a charge : ions
  
• a salt is built form positive metal-ions and negative non-metal ions.

forming of ions

• Sodium exchanges the electron in the outer shell with chlorine
• Sodium becomes Na⁺
• Chlorine becomes  Cl^-
• Na⁺ and  Cl^- attrack each other and form a lattice

Ionic Lattice

• Each Na⁺ is surrounded by  Cl^-  and vice versa
• during solid phase the lattice is in tact, no free moving particles.
• during liquid phase the lattice is no longer intact and particles can move freely.

salts in water

• bond between Na+ and Cl- is called ionic bond , very strong
• in dissolving a salt in water, the bond is broken down.

salts in water

• Each ion is surronded by watermolecules. 
• In an equation :
  NaCl (s) -> Na⁺ (aq) + Cl^- (aq)
• NaCl (aq) does not exist. It dissolves immediately.

Evaporation

When evaporating a salt solution, exactly the opposite process takes place:

Na+ (aq) + Cl- (aq) --> NaCl(s)

monoatomic ions ( one type of ions)

polyatomic ions  (page 174)

Polyatomic ions are atoms 

bonded together

 with a charge. 

These atoms are 

intergrated in the lattice

 

par 6.3

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