01 Introduction to Chemistry
02 Matter and the Atomic Structure
03 The Mole Concept, Chemical Formula and Equation
04 The Periodic Table of Elements
05 Chemical Bond
06 Acids, Bases and Salts
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3.4.1 Chemical Equation*

Writing Chemical Equations

A Balance Equation

According to the Law of Conservation of Mass, atoms cannot be created or eliminated in the process of chemical reaction. Therefore, the amount of atom of each element before reaction must be equal after 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 react with potassium iodide aqueous to produce lead(II) iodide precipitate and potassium nitrate aqueous.

Answer: