Balance Chemical Equation

Use '+' to separate multiple reactants/products and '→' or '=' for the arrow.
Enter a chemical equation above and click "Balance" to see the balanced equation with coefficients.
Balanced Equation

Step-by-Step Solution
Atom Count Table
Element Reactants Products Balanced

Interactive Guide

A chemical equation is a symbolic representation of a chemical reaction where the reactants (starting materials) are given on the left side and the products (resulting substances) on the right side. The two sides are separated by an arrow (→) indicating the direction of the reaction.

For example: H2 + O2 → H2O

Chemical equations must be balanced to satisfy the Law of Conservation of Mass, which states that matter cannot be created or destroyed in a chemical reaction. This means:

  • The same number of atoms of each element must appear on both sides of the equation
  • The total charge must be the same on both sides (for ionic reactions)

An unbalanced equation would imply that atoms are being created or destroyed, which violates this fundamental law.

  1. Write the unbalanced equation with correct formulas for all reactants and products
  2. Count atoms of each element on both sides
  3. Add coefficients (numbers in front of formulas) to balance atoms
  4. Start with elements that appear in only one compound on each side
  5. Balance polyatomic ions as single units if they appear unchanged on both sides
  6. Check your work by recounting all atoms
  7. Simplify coefficients to the smallest whole numbers

Example: Balancing H2 + O2 → H2O

  1. Count atoms: 2 H, 2 O → 2 H, 1 O
  2. Balance O by adding coefficient 2 to H2O: H2 + O2 → 2H2O
  3. Now H is unbalanced (2 vs 4), so add coefficient 2 to H2: 2H2 + O2 → 2H2O
  4. Verify: 4 H, 2 O → 4 H, 2 O (balanced!)

Practice Quiz

Test your balancing skills with these practice problems. Try to balance each equation before checking the solution.
Quiz 1: Basic Balancing

N2 + H2 → NH3

Solution:

  1. Count atoms: 2 N, 2 H → 1 N, 3 H
  2. Balance N by adding coefficient 2 to NH3: N2 + H2 → 2NH3
  3. Now H is unbalanced (2 vs 6), so add coefficient 3 to H2: N2 + 3H2 → 2NH3
  4. Verify: 2 N, 6 H → 2 N, 6 H (balanced!)

N2 + 3H2 → 2NH3

Quiz 2: Combustion Reaction

C3H8 + O2 → CO2 + H2O

Solution:

  1. Count atoms: 3 C, 8 H, 2 O → 1 C, 2 H, 3 O
  2. Balance C by adding coefficient 3 to CO2: C3H8 + O2 → 3CO2 + H2O
  3. Balance H by adding coefficient 4 to H2O: C3H8 + O2 → 3CO2 + 4H2O
  4. Now count O: 2 O → 10 O (3×2 + 4×1)
  5. Balance O by adding coefficient 5 to O2: C3H8 + 5O2 → 3CO2 + 4H2O
  6. Verify: 3 C, 8 H, 10 O → 3 C, 8 H, 10 O (balanced!)

C3H8 + 5O2 → 3CO2 + 4H2O

History

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Quick Reference

Common Elements
  • H - Hydrogen
  • He - Helium
  • Li - Lithium
  • Be - Beryllium
  • B - Boron
  • C - Carbon
  • N - Nitrogen
  • O - Oxygen
  • F - Fluorine
  • Ne - Neon
  • Na - Sodium
  • Mg - Magnesium
  • Al - Aluminum
  • Si - Silicon
  • P - Phosphorus
  • S - Sulfur
  • Cl - Chlorine
  • K - Potassium
  • Ca - Calcium
  • Fe - Iron
Common Polyatomic Ions
  • NH4+ - Ammonium
  • NO3- - Nitrate
  • NO2- - Nitrite
  • OH- - Hydroxide
  • CN- - Cyanide
  • MnO4- - Permanganate
  • CO32- - Carbonate
  • SO42- - Sulfate
  • SO32- - Sulfite
  • PO43- - Phosphate
  • CrO42- - Chromate
  • Cr2O72- - Dichromate
Example Equations
  • H2 + O2 → H2O
  • CH4 + O2 → CO2 + H2O
  • Fe + O2 → Fe2O3
  • Al + HCl → AlCl3 + H2
  • Na2CO3 + HCl → NaCl + H2O + CO2
Tips & Tricks
  • Start with elements that appear in only one compound on each side
  • Balance metals first, then nonmetals
  • Save H and O for last (they often appear in multiple compounds)
  • Treat polyatomic ions as single units when possible
  • For combustion reactions, balance C then H then O
  • Fractional coefficients are okay for intermediate steps
  • Always double-check your final equation