CHAPTER 5: IONIC COMPOUNDS

Question 1

what are ionic compounds

Answer 1

• chemical combination of metallic and non-metallic elements
• most rocks, minerals and gem stones are ionic compounds

Question 2

properties of ionic compounds

Answer 2

• have high melting and boiling points
• they are all solid at room temperature
• are hard but brittle (when a force pushes the ions, the cations repel each other so the crystal shatters)
• do not conduct electricity in the solid state
• are good conductors of electricity in the liquid state or when dissolved in water
• vary from very soluble to insoluble in water

Question 3

the ionic bonding model

Answer 3

• large number of cations and anions combine to form a three-dimensional lattice
• the 3D lattice is held together strongly by electrostatic forces of attraction between oppositely charged ions
  
  • called ionic bonding

Question 4

electrical conductivity of ionic compounds

Answer 4

• when ionic compounds dissolve in water, the ions move freely in the solution
• positive ions moved towards the negatively charged electrode and negative ions move towards the positively charged electrode

Question 5

uses of ionic compounds

Answer 5

hardness

• granite, limestone and sandstone are used as building stone

high melting point

• magnesium oxide and other ionic compounds are used to line furnaces

electrical conductivity

• ammonium chloride is used as an electrolyte in dry cell batteries
• electrolytes contain ions in solution and this allows the current to flow in the battery

other uses of ionic compounds

• sodium chloride is a flavouring agent and preservative in food

Question 6

precipitation reaction

Answer 6

• a precipitation reaction occurs if two solutions combine to form a new compound that is insoluble in water
• the insoluble compound formed in such as reaction is called a precipitate

Question 7

writing full equations for precipitation reactions

Answer 7

full equation

• the ionic formulas of the compounds
• the state (aqueous or solid)
• balance the equation
  
  • the ions not involved in forming the precipitate are called spectator ions

Question 8

writing ionic equations for precipitation reactions

Answer 8

• write down the formula of the precipitate on the RHS
• on the LHS, add the formulas of the ions that form the precipirate
  
  • include the states
  • include the charge of the ions
  • balance the equation