ChemVocab: Unit 3

:3

atomic mass

atomic mass

the mass of the atom in atomic mass units

atomic mass unit

a mass exactly equal to one twelfth the mass of one carbon-12 atom

mole (mol)

 the amount of substance that contains as many atoms, molecules, or particles as there are atoms in exactly 12 grams of the carbon-12 isotope

Avogadro’s number

 6.0221415 10^23, the number of atoms in a 12 grams of carbon

molar mass

the mass of one mole of a substance; 12 grams in a mole of carbon, 14 grams in a mole of nitrogen

molecular mass

the sum of the atomic masses (amu) in the molecule

percent composition by mass

percent by mass of each element in a compound

chemical reaction

a process in which a substance or substances is changed into one or more new substances

chemical equation

uses chemical symbols to show what happens during a chemical reaction

reactants

the starting materials in a chemical reaction

product

the substance formed as a result of a chemical reaction

stoichiometry

the quantitative study of reactants and products in a chemical reaction

mole method

the stoichiometric coefficients in a chemical equation can be interpreted as the number of moles of each substance

stoichiometric amounts

 the proportions indicated by the balanced equations

limiting reagent

the reactant used up first in a reaction

excess reagent

 the reactants present in quantities greater than necessary to react with the quantity of the limiting reagent

theoretical yield

the amount of product that would result if all of the limiting reagent reacted

actual yield

the amount of product actually obtained from a reaction, is almost always less than the theoretical yield

percent yield

the proportion of the actual yield to the theoretical yield, determines how efficient a given reaction is