Chemistry Stoichiometry

Question 1

A ___ is a pure substance composed of two or more elements in a fixed proportion

Answer 1

compound

Question 2

___ 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

Answer 2

ionic compounds

Question 3

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

Answer 3

molecular mass

Question 4

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

Answer 4

mole

Question 5

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

Answer 5

compound

Question 6

The mass of one mole of a ___ is called its molar mass or molar weight and is usually expressed as g/mol

Answer 6

compound

Question 7

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

Answer 7

equivalent

Question 8

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

Answer 8

compound

Question 9

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

Answer 9

equivalents

Question 10

___ is dependent on reaction conditions and is determined experimentally; however, on the exam, gram equivalent weight can be estimated from the molecular structure

Answer 10

gram equivalent weight

Question 11

The law of constant composition states that all ___ of a given compound will contain the same elements in identical mass ratios

Answer 11

samples

Question 12

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

Answer 12

sample

Question 13

The empirical ___ gives the simplest whole number ratio of the elements in the compound

Answer 13

formula

Question 14

The ___ gives the exact number of atoms of each element in the compound and is a multiple of the empirical formula

Answer 14

molecular formula

Question 15

As far as empirical formulas are concerned, the ___ for benzene is CH, whereas the molecular formula is C6H6

Answer 15

empirical formula

Question 16

For some ___ the empirical and molecular formulas are the same, as in the case of H2O

Answer 16

compounds

Question 17

An ionic compound, such as NaCl or CaCO3, will only have an ___ formula

Answer 17

empirical

Question 18

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

Answer 18

molecular

Question 19

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%

Answer 19

percent composition

Question 20

The percent composition of an element may be determined using either the ___ or molecular formula

Answer 20

empirical

Question 21

One can ___ the molecular formula if both the percent compositions and molecular mass of the compound are known

Answer 21

determine

Question 22

When ___ are mixed, they are seldom added in the exact stoichiometric proportions as shown in the balanced equation

Answer 22

reactants

Question 23

Because ___ are rarely added in the exact stoichiometric proportions as shown in the balanced equation, one of the reactants will be consumed first

Answer 23

reactants

Question 24

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

Answer 24

limiting reactant

Question 25

The reactant(s) that remains after all of the ___ is used up is called the excess reactant

Answer 25

limiting reactant

Question 26

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

Answer 26

theoretical yield

Question 27

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

Answer 27

isolated

Question 28

The term percent yield is used to ___ the relationship between the actual yield and the theoretical yield

Answer 28

express

Question 29

Percent yield = ___/theoretical yield x 100%

Answer 29

actual yield