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What Is the Difference Between a Chemical Reaction and Chemical Equation?

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A chemical equation describes the reactants, products, and quantities of chemicals in a reaction.

A chemical equation describes the reactants, products, and quantities of chemicals in a reaction.

Jeffrey Coolidge, Getty Images
What is the difference between a chemical reaction and the chemical equation? The terms are often used interchangeably, but they are technically different terms.

A chemical reaction is the process that occurs when one or more substances are changed into one or more new substances.

For example:
  • Hydrogen and oxygen gas combine to produce water.
  • Sodium chloride (table salt) dissociates in water to form sodium and chlorine ions.
  • Methane combusts in oxygen to form carbon dioxide, heat and water.
A chemical equation is a symbolic representation of a chemical reaction. Atomic symbols are used to represent the elements that take part in a reaction. Numbers are used to represent the ratios of reactants and products to produce the reaction and arrows point the direction a reaction occurs where the arrow points from reactants to products.

For example, using for the above chemical reactions:
  • 2 H2(g) + O2(g) → 2 H2O(ℓ)

    This chemical eqution reads: Two hydrogen gas molecules and one oxygen gas molecule produce two molecules of water.
  • NaCl(s) + H2O → Na+(aq) + Cl-(aq)

    One molecule of sodium chloride dissociates in water into one sodium ion and one chlorine ion.
  • CH4 + 2 O2 → CO2 + 2 H2O (&DeltaH = -891 kJ/mol)

    This equation shows one methane molecule and two oxygen gas molecules form a carbon dioxide molecule, two water molecules and release 891 kilojoules of heat.
To review:

Chemical reactions are processes where reactants become new products.
Chemical equations are symbolic representation of chemical reactions.

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