01 Introduction to Chemistry
02 The Structure of Atoms
03 Concept of Mole, Formulae and Equations
04 Periodic Table of Elements
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3.4.1 Chemical Equations

Writing Chemical Equations

A Balance Equation

According to the Law of Conservation of Mass, atoms cannot be created or eliminated in the process of a chemical reaction. Therefore, the amount of atom of each element before reaction must be equal after the reaction. 

Example:
Balance the following chemical equations:

  1. Mg +    O2 →    MgO
  2. CuO + H2 →    Cu + H2O
  3. Na +    H2O →    NaOH + H2
  4. Li +    Cl2 →    LiCl
Answer:
a.
2Mg +    O2 →    2MgO
 

b.

CuO + H2 →    Cu + H2O
 

c.

2Na +    2H2O →    2NaOH + H2
d.
2Li +    Cl2 →    2LiCl
Writing a Balance Equation

Example:
Lead(II) nitrate aqueous reacts with potassium iodide aqueous to produce lead(II) iodide precipitate and potassium nitrate aqueous.

Answer: