Balancing Equations Trainer

A balanced equation has the same number of atoms of each element on both sides. Change the coefficients and watch the atom counter and the scale until both sides match. Stuck? Ask for a hint, watch a worked example, or type any equation and have it balanced for you.

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How to balance an equation

Write the correct formulas for every reactant and product. Never change a subscript to balance an equation: that changes the substance. Only change the coefficients (the big numbers in front).
Count the atoms of each element on both sides. Treat a group like (OH) or SO₄ as one unit if it stays together.
Balance one element at a time. Start with elements that appear in only one substance on each side, leave hydrogen and oxygen until last, and balance a lone element (like O₂ or Fe) at the very end.
Check every element again, and make sure the coefficients are in the smallest whole-number ratio.

Why it matters: atoms are neither made nor destroyed in a chemical reaction (the law of conservation of mass), so the atoms you start with must all be there at the end.

Common tricks

Odd and even

If an element is odd on one side and even on the other (like 3 O in Fe₂O₃ and 2 O in O₂), double the substance with the odd number first.

Burning a hydrocarbon

Balance carbon (CO₂), then hydrogen (H₂O), then oxygen last. If oxygen comes out as a half, double everything.

Polyatomic ions

If SO₄ or NO₃ is unchanged on both sides, count it as one unit. It is much quicker than counting S and O separately.

Practise what you learned

Test yourself with chapter-wise MCQs and explanations:

Stoichiometry — Chemistry, HSSC-KPK First Year (1,113 questions)
Theories of Covalent Bonding and Shapes of Molecules — Chemistry, HSSC-KPK First Year (699 questions)
Stoichiometry — Chemistry, HSSC-Punjab First Year (953 questions)
Fundamentals of Chemistry — Chemistry, SSC-KPK Class 9 (1,095 questions)
Structure of Molecules — Chemistry, SSC-KPK Class 9 (1,551 questions)
Stoichiometry — Chemistry, SSC-Punjab Class 9 (544 questions)
Stoichiometry — Chemistry, SSC-Punjab Class 10 (649 questions)

State symbols and charges are not needed here. The tool checks that the atoms balance; it does not check whether the reaction really happens. Works offline: after your first visit the trainer is saved in your browser.