Reactant
Definition and meaning of Reactant in chemistry.
A reactant is a starting substance that is present at the very beginning of a chemical reaction and undergoes a fundamental chemical change to form entirely new products. Reactants are systematically consumed during the natural course of the reaction as their existing chemical bonds are broken and completely new chemical bonds are subsequently formed.
In more detail
In standard written chemical equations, the initial reactants are conventionally written on the left side of the directional yield arrow. The intrinsic chemical nature and the initial molar concentration of the reactants play a primary role in decisively determining both the specific type of chemical reaction that occurs and the thermodynamic rate at which it actively proceeds. In many practical chemical reactions, one particular reactant may be entirely consumed long before the other available reactants, acting effectively as the limiting reactant that ultimately dictates the absolute maximum theoretical yield of product that can possibly be formed. The remaining leftover reactants are therefore formally considered to be chemically in excess.
Key facts
| Field | General Chemistry |
|---|---|
| Chemical Role | Substance systematically consumed in a chemical reaction |
| Location in Equation | Conventionally written on the left side of the yield arrow |
In the direct chemical synthesis of liquid water (2H2 + O2 -> 2H2O), flammable hydrogen gas (H2) and reactive oxygen gas (O2) function as the essential starting reactants.
Frequently asked questions
What exactly is meant by the term limiting reactant?
The limiting reactant is the particular substance that is completely consumed first, thereby forcefully stopping the reaction and exclusively determining the absolute maximum yield of the product.