Chemistry· 5 min read
How to Balance Chemical Equations (Step by Step)
Balancing equations is about the law of conservation of mass: you must have the same number of each type of atom on both sides. You balance by adjusting coefficients (the big numbers in front), never the small subscripts.
The method
Work through it in this order and it stays manageable.
- •Write the unbalanced equation and count atoms of each element on both sides.
- •Balance one element at a time by adding coefficients.
- •Leave hydrogen and oxygen for last; do single elements first.
- •Recount after each change, and never alter subscripts.
Worked example
Balance H₂ + O₂ → H₂O. Oxygen: 2 on the left, 1 on the right → put a 2 in front of H₂O. Now H: 4 on the right, 2 on the left → put a 2 in front of H₂.
Result: 2H₂ + O₂ → 2H₂O. Four H and two O on each side — balanced.
Frequently asked questions
Why can I not change the subscripts?
Subscripts define the compound itself. Changing H₂O to H₂O₂ makes a different substance. Only coefficients (amounts) may change.
What does it mean for an equation to be balanced?
There is the same number of each kind of atom on both sides, reflecting that matter is conserved.