Balancing Chemical Equations (Lesson)

Balancing Chemical Equations

Introduction to Balancing Equations

● Balancing equations is essential in chemistry.
● It ensures the law of conservation of mass is

followed.
○ Matter is neither created nor destroyed

Understanding Reactants and Products

● Reactants are substances that start a chemical

reaction.

● Products are what you get after the reaction.

● Can you identify the reactants and products in this

equation: H₂ + O₂→ H₂O?

Coefficients and Subscripts

Coefficients - Big numbers that go in front of the molecule, tell us how many molecules there are in a set

Subscript - Little numbers that hang off the Atom. Tells us how many of each type of atom are in the set.

Multiple Choice

Look at the subscripts and tell me how many Carbon atoms are listed?

C₁₂H₂₂O₁₁

• 12
• 15
• 8
• 10

Multiple Choice

How many Hydrogen atoms are present?

2H₂O

• 1
• 3
• 4
• 2

Multiple Choice

How many Bromine atoms are listed?

12NaBr

• 10
• 14
• 8
• 12

Steps to Balance Equations

● Step 1: Take Inventory
● Step 2: Is it balanced?
● Step 3: Change Coefficients to balance

equation

Simple Example: H₂ + O₂ → H₂O

● Start with:

____H₂ + ____O₂→ ____H₂O

● Count:
● Adjust:

Example: Fe + O₂ → Fe₂O₃

●Start with
Count:
● Adjust:

Example: C₃H₈ + O₂ → CO₂ + H₂O

● Start with:
● Count:
● Adjust:

Fill in the Blank

What coefficient should be used to make the following balanced?

N₂O₂ ==> ____NO

Multiple Choice

How many HCl molecules do you need to balance this equation?

Mg + __HCl ==> MgCl₂ + H₂

• 1
• 3
• 4
• 2