Chemistry Stoichiometry Flashcards
A ___ is a pure substance composed of two or more elements in a fixed proportion
compound
___ do not form true molecules. In the solid state, they can be considered to be an extensive three-dimensional array of the charged particles of which the compound is composed. Because no actual molecule exists, molecular mass becomes meaningless, and the term formula mass is used in its place
ionic compounds
Like atoms, molecules can be characterized by their mass. The ___ (also known as molecular weight) is the sum of the atomic masses of the atoms in the molecule. Similarly the formula mass of an ionic compound is found by adding up the atomic masses of each constituent atom according to the empirical formula of the substance
molecular mass
A ___ is defined as the amount of a substance that contains the same number of particles found in a 12 g sample of cabon-12
mole
One mole of a ___ has a mass in grams equal to the molecular mass of that compound in amu and contains 6.022 x 10^23 molecules of the compound
compound
The mass of one mole of a ___ is called its molar mass or molar weight and is usually expressed as g/mol
compound
For instance, one mole of HCL can donate one mole of hydrogen ions, while one mole of H2SO4 can donate two moles of hydrogen ions. This difference is expressed using the term ___: one mole of HCL contains one equivalent of hydrogen ions, while one mole of H2SO4 contains two equivalents of hydrogen ions
equivalent
To determine the number of equivalents a ___ contains, a new measure of weight, called gram-equivalent weight (GEW), was developed such that:
equivalents = weight of compound/ gram equivalent weight and
gram equivalent weight = molar mass / n
where n is the number of equivalents per mole of the substance
compound
The number of ___ is usually either the number of hydrogen ions an Arrhenius or Bronsted-Lowry acid could donate per molecule or the number of hydroxyl groups an Arrhenius base could donate (or number of hydrogen ions a Bronsted-Lowry base could accept) in a reaction
equivalents
___ is dependent on reaction conditions and is determined experimentally; however, on the exam, gram equivalent weight can be estimated from the molecular structure
gram equivalent weight
The law of constant composition states that all ___ of a given compound will contain the same elements in identical mass ratios
samples
As the law of constant composition states, every ___ of H2O will contain two atoms of hydrogen for every atom of oxygen and therefore one gram of hydrogen for every eight grams of oxygen
sample
The empirical ___ gives the simplest whole number ratio of the elements in the compound
formula
The ___ gives the exact number of atoms of each element in the compound and is a multiple of the empirical formula
molecular formula
As far as empirical formulas are concerned, the ___ for benzene is CH, whereas the molecular formula is C6H6
empirical formula
For some ___ the empirical and molecular formulas are the same, as in the case of H2O
compounds
An ionic compound, such as NaCl or CaCO3, will only have an ___ formula
empirical
Note that given a ___ formula, the empirical formula for that molecule can be calculated by simplifying the ratio of the subscripts next to each component
molecular
To determine the ___ of an element X in a compound, the following formula is used: % composition = mass of X in Formula/ Formula Weight of Compound x 100%
percent composition
The percent composition of an element may be determined using either the ___ or molecular formula
empirical
One can ___ the molecular formula if both the percent compositions and molecular mass of the compound are known
determine
When ___ are mixed, they are seldom added in the exact stoichiometric proportions as shown in the balanced equation
reactants
Because ___ are rarely added in the exact stoichiometric proportions as shown in the balanced equation, one of the reactants will be consumed first
reactants
The reactant that is consumed first is known as the ___ or limiting reagent because it limits the amount of product that can be formed in the reaction
limiting reactant
The reactant(s) that remains after all of the ___ is used up is called the excess reactant
limiting reactant
The ___ is the amount of product that can be predicted from a balanced equation, assuming that all of the limiting reagent has been used, no competing side reactions have occurred, and all of the product has been collected
theoretical yield
The theoretical yield is seldom obtained in real-world conditions; therefore, chemists speak of the actual yield, which is the amount of product ___ from the reaction experimentally
isolated
The term percent yield is used to ___ the relationship between the actual yield and the theoretical yield
express
Percent yield = ___/theoretical yield x 100%
actual yield
