Chemical Reaction vs. Chemical Equation

What is the difference between a chemical reaction and the chemical equation? These terms are often used interchangeably, but although they're related, they're different things. A chemical reaction is a process that occurs when one or more substances are changed into one or more new substances. For example:

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What Is a Chemical Reaction?

By Anne Marie Helmenstine, Ph.D.

• 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.

On the other hand, a chemical equation is the symbolic representation of a chemical reaction. Atomic symbols are used to represent the elements that take part in a reaction. The numbers represent the ratios of reactants and products that produce the reaction. Arrows point the direction a reaction occurs, with the arrow pointing from reactants to products. For example, using for the above chemical reactions:

• 2 H₂(g) + O₂(g) → 2 H₂O(ℓ)
  This chemical equation 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 in which reactants become new products.
Chemical equations are the symbolic representation of chemical reactions.