Definition

1. Noun:
   • A chemical substance present at the start of a chemical reaction: A "reactant" is a substance that is consumed or undergoes change during a chemical reaction to form new products.

Usage

• The term "reactant" is used specifically in the context of chemistry to identify the starting materials in a reaction. It is a countable noun.
• In a chemical equation, reactants are typically written on the left side of the arrow.
• Example: "In the reaction between hydrogen and oxygen to form water, both hydrogen and oxygen are reactants."

Examples

• Noun:
  • The concentration of the reactant decreases as the reaction proceeds.
  • Identifying the limiting reactant is crucial for calculating the theoretical yield of a product.
  • The experiment requires measuring the mass of each reactant before mixing.

Advanced Usage

• "Limiting reactant": The reactant that is completely consumed first in a chemical reaction, thus determining the maximum amount of product that can be formed.
  • In the synthesis of ammonia, nitrogen is often the limiting reactant if hydrogen is supplied in excess.

Variants and Related Words

• Reaction (n): The process in which reactants are transformed into products.
  • The chemical reaction produced a significant amount of heat.
• Reactive (adj): Tending to participate readily in reactions.
  • Sodium is a highly reactive metal.

Synonyms

• Reagent: A substance used to cause a chemical reaction, especially to detect, measure, or produce other substances. (Note: While often used interchangeably with "reactant" in some contexts, "reagent" can imply a substance added to bring about a reaction, whereas "reactant" is a more general term for any starting material.)
• Starting material: A more general term for any substance used at the beginning of a process.

Related Phrases

• "Reactant mixture": The combination of all reactants before a reaction begins.
  • The reactant mixture was heated to 80 degrees Celsius.
• "Reactant side": Referring to the left side of a chemical equation where reactants are listed.
  • Balance the equation by adjusting coefficients on the reactant side.

Noun

1. a chemical substance that is present at the start of a chemical reaction