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Balancing Chemical Equations
Step-by-Step Guide with Practice Problems
Learn the essential skill of balancing chemical equations with our comprehensive guide. Understand the process with clear examples and test your knowledge with practice problems.
Why It Matters
Balancing equations demonstrates the Law of Conservation of Mass, showing that atoms are neither created nor destroyed in chemical reactions.
Key Rule
Only add coefficients in front of compounds, never change the subscripts within compounds as this would change the substance.
Practice Makes Perfect
Use our practice problems with solutions to test your understanding and improve your equation balancing skills.
Why Balance Chemical Equations?
Balancing chemical equations is a fundamental skill in chemistry that helps us understand the relationships between different elements and compounds in a reaction. It demonstrates the Law of Conservation of Mass, which states that matter cannot be created or destroyed in a chemical reaction.
Step-by-Step Guide to Balancing Equations
Write the Chemical Equation
Start by writing the chemical equation for the reaction you want to balance. A chemical equation shows the reactants on the left side and the products on the right side, separated by an arrow.
Example: Reaction between hydrogen gas (H₂) and oxygen gas (O₂) to produce water (H₂O):
Count the Atoms on Each Side
Count the number of atoms of each element on both sides of the equation. This includes the atoms in both the reactants and the products.
For our example:
- Hydrogen (H): 2 atoms on left, 2 atoms on right
- Oxygen (O): 2 atoms on left, 1 atom on right
Choose an Element to Start Balancing
Select an element that appears in more than one molecule on either side of the equation. In our example, oxygen (O) is a good choice because it appears in two molecules on the left side and one molecule on the right side.
Add Coefficients
To balance the number of oxygen atoms, add a coefficient (a number in front of the molecule) to the molecule(s) that contain the element you chose. The coefficient multiplies the number of atoms in that molecule.
We balance oxygen by adding a coefficient of 2 in front of the water molecule:
Now we have:
- Hydrogen (H): 2 atoms on left, 4 atoms on right
- Oxygen (O): 2 atoms on left, 2 atoms on right
Check the Balance
After adding the coefficient, check if the equation is balanced. Go back and count the atoms of the element you just balanced and verify that they are now equal on both sides.
Continue Balancing
If the equation is not yet balanced, repeat steps 3 to 5 for another element until all elements are balanced on both sides.
For our example, we now need to balance hydrogen by adding a coefficient of 2 in front of H₂:
Now we have:
- Hydrogen (H): 4 atoms on left, 4 atoms on right
- Oxygen (O): 2 atoms on left, 2 atoms on right
Practice Problems
Try balancing these chemical equations on your own. Check your answers against the solutions provided.
Problem 1
Problem 2
Problem 3
Problem 4
Problem 5
Problem 6
Solutions to Practice Problems
Check your answers here. Remember that there might be multiple ways to balance equations, but the ratios should match these solutions.
| Problem | Balanced Equation |
|---|---|
| 1 | CH₄ + 2O₂ → CO₂ + 2H₂O |
| 2 | 2KI + Cl₂ → 2KCl + I₂ |
| 3 | 2HCl + Ca(OH)₂ → CaCl₂ + 2H₂O |
| 4 | K₃PO₄ + 3HCl → 3KCl + H₃PO₄ |
| 5 | 3CaSO₄ + 2AlBr₃ → 3CaBr₂ + Al₂(SO₄)₃ |
| 6 | 3Mg(NO₃)₂ + 2K₃PO₄ → Mg₃(PO₄)₂ + 6KNO₃ |
Key Points to Remember
- Chemical equations must obey the Law of Conservation of Mass
- Only add coefficients, never change subscripts
- Start with elements that appear only once on each side
- Always double-check your atom counts after balancing
- Practice with a variety of equation types
- Look for elements that are already balanced
- Balance polyatomic ions as groups when possible