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Stoichiometry Terms

Actual Yield

When a chemical reaction is completed, this is the amount of product that you actually make (the amount of stuff you can weigh).

Atomic Mass

The mass of an atom expressed in atomic mass units (amu).

Avogadro's Number

A number equal to 6.023 × 1023. It is also equal to the number of atoms or molecules in one mole of a substance.

Chemical Equation

A chemical equation is a representation of a chemical reaction where the reactants are given on the left hand side of an arrow followed by the products of a reaction on the right hand side.

Chemical Reaction

A process that converts one or more chemicals into a different chemical (or chemicals).


Two or more forms of the same element that contain equal number of protons but different number of neutrons in their nuclei.

Law Of Conservation Of Mass

A scientific principle that states that matter cannot be created nor destroyed.

Limiting Reagent

The limiting reagent is the chemical in a reaction that determines how far a reaction can proceed or how much product a reaction can make.


Visible to the naked, or unaided, eye.


Extremely small; visible with a microscope.

Molar Mass

The mass in one mole of a substance.


A measurement of an amount of a substance, always equal to 6.023 × 1023 units.


A group of atoms bonded together.

Percent Composition

The percentage by mass of each element in a compound.

Percent Yield

The actual yield of a chemical reaction divided by the theoretical yield times 100%.

Physical State

The state of the matter: solid, liquid, or gas.


In a chemical reaction, the product is the chemical outcome. It appears to the right of the arrow in a chemical equation.


In a chemical reaction, the reactant is the starting chemical(s). It appears to the left of the arrow in a chemical equation.


The set proportions in which elements or compounds react with one another.

Theoretical Yield

The quantity of product obtained from the complete conversion of the limiting reagent in a chemical reaction. This is how much product a reaction would give us if we lived in a perfect world and no errors were allowed.

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