Modern States Unit 2

Question 1

What is a crucial topic in chemistry that deals with the amounts of substances?

Answer 1

Stoichiometry

Question 2

What are important concepts that help determine stoichiometric amounts

Answer 2

Molar and formula masses

Question 3

Coefficients in chemical reactions do not indicate ratios of reactants and products in terms of what?

Answer 3

masses

Question 4

What is calculated by multiplying the molar mass of the substance by the number of moles?

Answer 4

the mass of a substance produced

Question 5

What is the unit of measurement for amount of substance, a quantity proportional to the number of elementary entities of a substance?

Answer 5

The mole

Question 6

What type of reagent is the reactant that is present in the smallest amount?

Answer 6

Limiting Reagent

Question 7

What type of reagent is whatever is remaining after the reaction?

Answer 7

Excess reagent

Question 8

What type of reagent is the one with leftover moles after the reaction?

Answer 8

Excess reagent

Question 9

Balancing chemical reactions involves ensuring that the numbers of each type are what?

Answer 9

are the same on both sides of the reaction

Question 10

What type of reagent gets completely used up in the reaction?

Answer 10

Limiting Reagent

Question 11

What type of reagent determines the outcome of the reaction?

Answer 11

Limiting Reagent

Question 12

Coefficients in chemical reactions indicate ratios in terms of what?

Answer 12

molecules or moles

Question 13

Coefficients in chemical reactions do not indicate what in terms of molecules or moles, not masses?

Answer 13

ratios of reactants and products

Question 14

Aqueous solutions involve dissolving substances in what?

Answer 14

water

Question 15

What occurs when ionic substances dissolve in water, producing more ions that conduct electricity?

Answer 15

Dissociation

Question 16

What type of electrolytes dissociate completely?

Answer 16

Strong

Question 17

What type of electrolytes only conduct electricity to a limited extent

Answer 17

weak

Question 18

Understanding the formula and dissociation of substances can help calculate the what of ions in a solution

Answer 18

concentration

Question 19

For what type of substances, the formula represents the numbers and types of atoms composing a single molecule of
the substance?

Answer 19

covalent

Question 20

What type of compounds are composed of discrete cations and anions combined in ratios to yield electrically neutral bulk matter?

Answer 20

Ionic compounds

Question 21

what traits are the identity of a substance is defined by?

Answer 21

• types of atoms or ions it contains
• the quantity of each type of atom or ion

Question 22

How formula mass for an ionic compound is calculated in the same way as the formula mass for covalent compounds

Answer 22

by summing the average atomic masses of all the atoms in the compound’s formula

formula for ionic compound doesn’t represent composition of a discrete molecule, so it may
not correctly be referred to as the molecular mass

Question 23

True or false

Formula mass for an ionic compound is not calculated in the same way as the formula mass for covalent.

Answer 23

False

Question 24

The amount of product that may be produced by a reaction under specified conditions is called what?

as calculated per the
stoichiometry of an appropriate balanced chemical equation

Answer 24

theoretical yield

Question 25

What is defined as the amount of substance containing the same number of discrete entities as the number of atoms in a sample of pure 12C weighing exactly 12 g? | (such as atoms, molecules, and ions)

Answer 25

A mole

Question 26

The number of entities composing a mole is a constant is properly reported with an explicit unit of “per mole,” a conveniently rounded version being What?

Answer 26

6.022 × 1023/mol ## Footnote fundamental constant named Avogadro’s number (NA) or the Avogadro constant in honor of Italian scientist Amedeo Avogadro.

Question 27

# True or False 1 mole of any element contains the same number of atoms as 1 mole of any other element.

Answer 27

True ## Footnote The masses of 1 mole of different elements, however, are different, since the masses of the individual atoms are drastically different.

Question 28

What is defined as the percentage by mass of each element in the compound

Answer 28

percent composition

Question 29

empirical formulas are derived from experimentally measured element masses by what three steps?

Answer 29

1. Deriving the number of moles of each element from its mass 2. Dividing each element’s molar amount by the smallest molar amount to yield subscripts for a tentative empirical formula 3. Multiplying all coefficients by an integer, if necessary, to ensure that the smallest whole-number ratio of subscripts is obtained

Question 30

Molecular formulas are derived how?

Answer 30

by comparing the compound’s molecular or molar mass to its empirical formula mass

Question 31

What is empirical formula mass ?

Answer 31

the sum of the average atomic masses of all the atoms represented in an empirical formula ## Footnote If we know the molecular (or molar) mass of the substance, we can divide this by the empirical formula mass units per molecule

Question 32

empirical formula

Answer 32

molecular or molar mass (amu or g per mol) / empirical formula mass (amu or g per mol) = n formula units or molecule

Question 33

The relative amounts of reactants and products represented in a balanced chemical equation are often referred to as what?

Answer 33

stoichiometric amounts

Question 34

The amount of product obtained is called the what?

Answer 34

actual yield

Question 35

forlmula of percent yield

Answer 35

percent yield = actual yield/ theoretical yield × 100%

Question 36

What is quantitative analysis?

Answer 36

the determination of the amount or concentration of a substance in a sample

Question 37

he described approach to measuring vinegar strength was an early version of the analytical technique known as what?

Answer 37

titration analysis

Question 38

A typical titration analysis involves the use of what?

Answer 38

a buret

Question 39

special dyes called what are added to the sample solutions to impart a change in color at or very near the equivalence point of the titration

Answer 39

indicators

Question 40

the volume of titrant actually measured is called the what?

Answer 40

end point

Question 41

Name reasons why the reaction's actual yield is smaller than the theoretical yield.

Answer 41

1. no reaction actually ever goes 100% to completion 2. there is experimental error in recovering all of the product. 3. the chemical reaction is not 100% efficient

Question 42

What is a way were a sample is subjected to some treatment that causes a change in the physical state of the analyte that permits its separation from the other components of the sample?

Answer 42

gravimetric analysis

Question 43

The elemental composition of hydrocarbons and related compounds may be determined via a gravimetric method known as what?

Answer 43

combustion analysis

Question 44

In a what, a weighed sample of the compound is heated to a high temperature under a stream of oxygen gas, resulting in its complete combustion to yield gaseous products of known identities.

Answer 44

combustion analysis

Question 45

The substances undergoing reaction are called what and their formulas are placed on which side of the equation.

Answer 45

reactants the left

Question 46

The substances generated by the reaction are called what, and their formulas are placed on which sight of the equation

Answer 46

products the right

Question 47

The relative numbers of reactant and product species are represented by what? | (numbers placed immediately to the left of each formula) ## Footnote A coefficient of 1 is typically omitted.

Answer 47

coefficients

Question 48

# True or false Substances with relatively large solubilities are said to be soluble in water

Answer 48

True

Question 49

balanced meaning that equal numbers of atoms for each element involved in the reaction are represented on the reactant and product sides

Answer 49

meaning that equal numbers of atoms for each element involved in the reaction are represented on the reactant and product sides

Question 50

What are ions whose presence is required to maintain charge neutrality

Answer 50

spectator ions

Question 51

Define solubility

Answer 51

The extent to which a substance may be dissolved is quantitatively expressed

Question 52

What reaction is one in which dissolved substances react to form one (or more) solid products.

Answer 52

precipitation ## Footnote Many reactions of this type involve the exchange of ions between ionic compounds in aqueous solution and are sometimes referred to as double displacement, double replacement, or metathesis reactions.

Question 53

A substance will precipitate when solution conditions are what?

Answer 53

conditions are such that its concentration exceeds its solubility

Question 54

Substances with relatively low solubilities are said to be what and these are the substances that readily precipitate from solution?

Answer 54

insoluble

Question 55

What is a substance that will dissolve in water to yield hydronium ions

Answer 55

acid

Question 56

Acids that completely dissolve in water to yield hydronium ions are called what?

Answer 56

strong acid

Question 57

What only partially react with water, leaving a large majority of dissolved molecules in their original form and generating a relatively small amount of hydronium ions

Answer 57

weak acids

Question 58

hydroxides that completely dissociate in water, are considered what?

Answer 58

strong bases

Question 59

What is a specific type of acid-base reaction in which the reactants are an acid and a base, the products are often a salt and water, and neither reactant is the water itself

Answer 59

A neutralization reaction

Question 60

These equations show that Na atoms lose electrons while Cl atoms (in the Cl2 molecule) gain electrons, the “s” subscripts for the resulting ions signifying they are present in the form of a solid ionic compound.

Answer 60

half-reaction

Question 61

species that is oxidized

Answer 61

reducing agent

Question 62

species that is reduced

Answer 62

oxidizing agent

Question 63

1.loss of electrons 2.gain of electrons

Answer 63

oxidation reduction

Question 64

What is an element in a compound is the charge its atoms would possess if the compound was ionic

Answer 64

oxidation number (or oxidation state)

Question 65

What are those in which one or more elements involved undergo a change in oxidation number

Answer 65

Oxidation-reduction (redox) reactions

Question 66

What reactions are redox reactions in which an ion in solution is displaced (or replaced) via the oxidation of a metallic element?

Answer 66

Single-displacement (replacement)

Question 67

# Define: spontaneous process

Answer 67

a process that occurs under specified conditions without the requirement of energy from some external source | The formation of a solution is an example of a spontaneous

Question 68

What is the thing that is produced when the strengths of the intermolecular forces of attraction between solute and solvent species in a solution are no different than those present in the separated components, the solution is formed with no accompanying energy change?

Answer 68

an ideal solution

Question 69

What is a stepwise process in which energy is consumed to overcome solute-solute and solvent-solvent attractions *(endothermic processes)* and released when solute-solvent attractions are established?

Answer 69

the formation of a solution

Question 70

When some substances are dissolved in water, they undergo either a physical or a chemical change that yields ions in solution. These substances constitute an important class of compounds called what?

Answer 70

electrolytes

Question 71

Substances that do not yield ions when dissolved are called what?

Answer 71

nonelectrolytes

Question 72

If the physical or chemical process that generates the ions is essentially 100% efficient (all of the dissolved compound yields ions), then the substance is known as a what?

Answer 72

strong electrolyte

Question 73

If only a relatively small fraction of the dissolved substance undergoes the ion-producing process, it is called a what?

Answer 73

weak electrolyte

Question 74

The electrostatic attraction between an ion and a molecule with a dipole is called what?

Answer 74

an ion-dipole attraction

Question 75

When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This process represents a physical change known as what?

Answer 75

dissociation

Question 76

The solubility of a solute in a particular solvent is the maximum concentration that may be achieved under given conditions when the what happens?

Answer 76

dissolution process is at equilibrium

Question 77

When a solute’s concentration is equal to its solubility, the solution is said to be what?

Answer 77

saturated

Question 78

If the solute’s concentration is less than its solubility, the solution is said to be what?

Answer 78

unsaturated