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How are reactants and products shown in a chemical equation?
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chemical reaction
Log burning in a fire. Burning wood is an example of a chemical reaction in which wood in the presence of heat and oxygen is transformed into carbon dioxide, water vapor, and ash.
In a chemical equation, reactants and products are represented using chemical symbols and organized by standard convention:1
- Placement: Reactants, which are the substances present at the start of a reaction, are written on the left side. Products, which are the substances formed as a result of the reaction, are written on the right side.12
- Arrows: A single arrow () between the two sides denotes an irreversible reaction, while a double arrow indicates a reversible reaction.1
- Coefficients: Numbers called coefficients are placed in front of chemical formulas to indicate the number of molecules involved. These are adjusted to ensure the equation is balanced, meaning the same number of atoms of each element appears on both sides, in accordance with the law of conservation of mass.123
By following these conventions, chemists can accurately depict the stoichiometry of a reaction, showing how substances are transformed while ensuring that matter is neither created nor destroyed.13