Chapter 1: Chemical Reactions and Equations
This chapter introduces chemical reactions, how to write and balance chemical equations, and different types of chemical reactions.
Q1. Why should a magnesium ribbon be cleaned before burning in air?
Solution
Magnesium ribbon should be cleaned before burning because:
• Magnesium ribbon has a thin layer of magnesium oxide (MgO) on its surface due to reaction with air.
• This layer prevents the ribbon from burning properly.
• Cleaning with sandpaper removes this oxide layer, exposing fresh magnesium metal for a bright and clean combustion.
Q2. Balance the following chemical equation:2 O → Fe3 O4 + H2
Solution
We balance the atoms of each element on both sides:
Unbalanced: Fe + H2 O → Fe3 O4 + H2 2 O → Fe3 O4 + H2 2 O → Fe3 O4 + H2 2 O → Fe3 O4 + 4H2 2 O → Fe3 O4 + 4H2
2Mg + O₂
2MgO
Combination
2Pb(NO₃)₂
2PbO + 4NO₂ + O₂
Decomposition
Fe + CuSO₄
FeSO₄ + Cu
Displacement
Na₂SO₄ + BaCl₂
BaSO₄ + 2NaCl
Double Displacement
Types of Chemical Reactions
Types of Chemical Reactions: