Chapter 8 part 3: How are oxides classified?

Question 1

What are the oxides that metals and non-metals react together to form?

Answer 1

• Both metals, and non-metals react with oxygen in (the) air/atmosphere to form oxides.
• Most of these oxides have basic/acidic properties, which are affected by the metallic/non-metallic character of the element bonded to oxygen.

Question 2

How are acidic oxides formed?

Answer 2

• Most non-metals react with oxygen to form acidic oxides.
• E.g. of acidic oxides: Sulfur dioxide (SO2), sulfur trioxide (SO3), and caron dioxide (CO2).

Question 3

What happens when sulfur dioxide , sulfur trioxide, and carbon dioxide dissolves in water?

Answer 3

• When sulfur dioxide is dissolved in water, it forms sulfurous acid (H2SO3).
• When sulfur trioxide is dissolved in water, it forms sulfuric acid (H2SO4)
• When carbon dioxide is dissolved in water, it forms carbonic acid (H2CO3).

Question 4

What is an acidic oxide + alkalis reaction?

Answer 4

• Acidic oxides react with alkalis to form salts and water.
• E.g. Sulfur dioxide + potassium hydroxide –> potassium sulfite + water
  SO2 (g) + 2KOH (aq) –> K2SO3 (aq) + H2O (l)
• E.g. Carbon dioxide + sodium hydroxide –> sodium carbonate + water
  CO2 (g) + 2 NaOH (aq) –> Na2 CO3 (aq) + H2O (l)

Question 5

How are basic oxides formed?

Answer 5

• Most metals react with oxygen to form basic oxides.
• E.g. of basic oxides: Magnesium oxide (MgO)

Question 6

What is a basic oxide + acid reaction?

Answer 6

• Basic oxides react with acids to form salts and water.
• E.g. Magnesium oxide + nitric acid –> magnesium nitrate + water
  MgO (s) + 2HNO3 (aq) –> Mg (NO3)2 (aq) + H2O (l)

Question 7

How are neutral oxides formed?

Answer 7

• Some non-metals react with oxygen to form neutral oxides.
• These oxides are neither acidic nor basic.
• E.g. of neutral oxide: Carbon monoxide (CO), nitrogen monoxide (NO), and water (H2O)

Question 8

How are amphoteric oxides formed?

Answer 8

• Some metals react with oxygen to form amphoteric oxides.
• E.g. of amphoteric oxides: Aluminium oxide (Al2 O3), and zinc oxide (ZnO).
• Amphoteric oxides have both acidic and basic properties. Thus, they can react with both bases and acids.

2 examples:
1) - Al2 O3 (s) + 2KOH (aq) –> 2 KAlO2 (aq) + H2O (l)
- Al2 O3 (s) + 6HNO3 (aq) –> 2 Al (NO3)3 (aq) + 3H2O (l)

2) - ZnO (s) + 2KOH (aq) –> K2 ZnO2 (aq) + H2O (l)
- ZnO (s) + 2HNO3 (aq) –> Zn (NO3)2 (aq) + H2O(l)