HESI A2 - Stoichiometry - Key Terms and Concepts

Stoichiometry

The study of quantitative relationships between reactants and products in chemical reactions.

Mole

A unit used to measure the amount of a substance, equal to Avogadro's number of particles.

Avogadro's Number (6.022 × 10²³)

The number of particles (atoms, molecules, ions) in one mole of a substance.

Molar Mass

The mass of one mole of a substance, expressed in grams per mole.

Balanced Equation

A chemical equation where the number of atoms for each element is equal on both sides.

Reactant

A substance that undergoes change during a chemical reaction.

Product

A substance formed as a result of a chemical reaction.

Limiting Reactant

The reactant that is completely consumed in a reaction, limiting the amount of product formed.

Excess Reactant

The reactant that remains after a reaction is complete because it is not fully consumed.

Theoretical Yield

The maximum amount of product that can be formed from a given amount of reactants.

Actual Yield

The amount of product actually obtained from a reaction.

Percent Yield

The ratio of actual yield to theoretical yield, expressed as a percentage.

Mole Ratio

The ratio of moles of one substance to another in a balanced chemical equation.

Empirical Formula

The simplest whole-number ratio of atoms of each element in a compound.

Molecular Formula

The actual number of atoms of each element in a molecule of a compound.

Combustion Analysis

A technique used to determine the empirical formula of a compound by burning it and analyzing the products.

Hydrate

A compound that contains water molecules as part of its crystal structure.

Anhydrous Compound

A compound that does not contain water molecules.

Molar Volume

The volume occupied by one mole of a gas at standard temperature and pressure.

Standard Temperature and Pressure (STP)

A set of conditions used for comparing gases, defined as zero degrees Celsius and one atmosphere of pressure.

Ideal Gas Law

A law that relates the pressure, volume, temperature, and number of moles of a gas.

Gas Stoichiometry

The study of quantitative relationships involving gases in chemical reactions.

Density

The mass of a substance per unit volume.

Concentration

The amount of solute present in a given quantity of solvent or solution.

Molarity

The number of moles of solute per liter of solution.

Molality

The number of moles of solute per kilogram of solvent.

Dilution

The process of reducing the concentration of a solution by adding more solvent.

Titration

A laboratory technique used to determine the concentration of a solute in a solution by reacting it with a solution of known concentration.

Equivalence Point

The point in a titration where the moles of acid equal the moles of base.

Endpoint

The point in a titration where the reaction is complete, often indicated by a color change.

Indicator

A substance that changes color in response to changes in pH, used to determine the endpoint of a titration.

Standard Solution

A solution with a precisely known concentration, used in titrations.

Stoichiometric Coefficient

The number written before a substance in a balanced equation, indicating the number of moles involved.

Mass-Mass Stoichiometry

Calculations involving the masses of reactants and products in a chemical reaction.

Volume-Volume Stoichiometry

Calculations involving the volumes of gases in a chemical reaction.

Mass-Volume Stoichiometry

Calculations involving the mass of a substance and the volume of a gas in a chemical reaction.

Percent Composition

The percentage by mass of each element in a compound.

Law of Conservation of Mass

The principle that mass is neither created nor destroyed in a chemical reaction.

Law of Definite Proportions

The principle that a compound always contains the same elements in the same proportion by mass.

Law of Multiple Proportions

The principle that when two elements form more than one compound, the ratios of the masses of one element to a fixed mass of the other are small whole numbers.

Stoichiometric Calculations

Calculations used to determine the quantities of reactants and products in a chemical reaction.

Excess Reactant Calculations

Calculations to determine the amount of excess reactant remaining after a reaction.

Limiting Reactant Calculations

Calculations to determine the amount of product formed based on the limiting reactant.

Empirical Formula Calculations

Calculations to determine the simplest whole-number ratio of atoms in a compound.

Molecular Formula Calculations

Calculations to determine the actual number of atoms of each element in a molecule.

Combustion Stoichiometry

Calculations involving the burning of a substance in oxygen to produce products.

Solution Stoichiometry

Calculations involving reactions in solution, often using molarity.

Gravimetric Analysis

A technique used to determine the amount of a substance by measuring its mass.

Volumetric Analysis

A technique used to determine the concentration of a solution by measuring its volume.

Stoichiometric Relationships

The relationships between the quantities of reactants and products in a chemical reaction.

Gram Formula Mass

The mass of one mole of a compound.

Mole-Mass Stoichiometry

Calculations involving moles and masses.

Mole-Mole Stoichiometry

Calculations involving moles of reactants and products.