Balancing chemical equations trainer

Formulae before coefficients

Subscripts belong to the substance. Coefficients tell you how many particles react. Once a formula is correct, leave it alone and balance by changing the number in front.

Fractional coefficients

Fractions are valid stoichiometric coefficients. For an ordinary symbol equation, they can be used while working and then scaled to the smallest whole-number ratio. An enthalpy equation defined for exactly one mole may correctly finish with coefficients such as ½ or 3½.

Common reaction patterns

• acid + metal → salt + hydrogen
• acid + carbonate → salt + water + carbon dioxide
• acid + hydroxide → salt + water
• hydrocarbon + oxygen → carbon dioxide + water

Redox equations

For harder equations, match the total increase and decrease in oxidation state. Half-equations must balance both atoms and charge before they are combined.