Chapter 8

Question 1

In the mass/molar/atoms conversion,

if (mass==amu), then what formula is used to solve?

Answer 1

{atoms = 1 atoms}

Question 2

In the mass/molar/atoms conversion,

if (mass==grams), then what formula is used to solve?

Answer 2

{atoms = 1 Na atoms / mass}

Question 3

In the mass/molar/atoms conversion,

if (mass==moles), then what formula is used to solve?

Answer 3

{moles = 1 Na atoms / 1 mole}

Question 4

The _____ _____ mass of an element is massed average of masses of all isotopes.

Answer 4

average atomic mass

Question 5

The _____ mass of a substance is the mass of 1 mole of the substance. (in grams)

Answer 5

molar mass

Question 6

The _____ _____ of an element present in a compound can be obtained by comparing the mass of the particular element present in 1 mole of the compound to the molar mass of the compound.

Answer 6

mass fraction

Question 7

The mass fraction of an element present in a compound can be obtained by comparing the mass of the particular element present in 1 mole of the compound to the _____ mass of the compound.

Answer 7

molar mass

Question 8

To determine the _____ formula of a new compound, the composition of the compound by mass must be known.

Answer 8

empirical formula

Question 9

To determine the _____ formula of the compound, the molar mass of the compound must also be known.

Answer 9

molecular formula

(Composition of the compound by mass and molar mass of the compound must be known before its molecular formula can be determined.)

Question 10

In unit analysis, you are essentially multiplying by a ratio that equals “______“.

Answer 10

one

Question 11

Avogadro’s number = _____ _{<span>E</span>} _____

Answer 11

_6.022_E23

(or 6.022x10²³)

Question 12

The _____ _____ mass of an element is equal to the sum of masses of it’s isotopes, each multiplied by it’s natural abundance.

Answer 12

average atomic mass

Question 13

The _____ _____ Unit (or _____) is 1/12 the mass of an atom of carbon 12.

In other terms, it is the average of the proton rest mass and the neutron rest mass. Approximately 1 ____ = _____ g.

Answer 13

Atomic Mass Unit (or AMU)

1 AMU = 1.66E-24 g

( in grams)

Question 14

In samples where the ratio of the masses is the same as the ratio of the masses of individual atoms, they always contain the same number of _____.

Answer 14

atoms

Question 15

In a sample where all elements are weighed, each sample has a ____\_ equal to that element’s average atomic mass in grams. These samples all contain the same number of atoms.

Answer 15

mass

Question 16

The _____ (or _____) is a number of carbon atoms in exactly 12 grams of pure ¹²C

Answer 16

mole (or mol),

Question 17

The _____ number is one mole that represents 6.022_E23 units.

Answer 17

Avogadro

Question 18

The _____ (or _____) is a number equal to the number of carbon atoms in 12.01 g. of carbon.

(in grams)

Answer 18

mole (mol)

(This is slightly different than SI unit’s standards.)

Question 19

In any sample, one mole of anything is ______ units of that substance.

Answer 19

6.022_E23

Question 20

In these samples of pure elements, they contain the same number of ____\_ or 1 _____.

Answer 20

atoms or 1 mole

Question 21

In a sample of pure graphite (a form of carbon),

it weights _____ g.

Answer 21

12.01 g

(why is this important? who knows!)

Question 22

In a sample of an element with a mass equal to that element’s average atomic mass expressed in grams contains ___ _____ of atoms.

Answer 22

1 mole

Question 23

A _____ _____ is fundamentally a collection of atoms.

Answer 23

chemical compound

Question 24

The _____ mass is the mass in grams of mole of a compound

Answer 24

molar mass

Question 25

The **\_\_\_\_\_** weight was traditionally used, instead of molar mass.

Answer 25

_molecular_ weight

Question 26

The molecular weight and molar mass are **\_\_\_\_\_**, they mean the **\_\_\_\_\_** thing.

Answer 26

_same_, they mean the _same_ thing. ## Footnote *(Because the term molar mass more accurately describes the concept, it will be used in this text.)*

Question 27

The **molar mass footnote** of any substance is the mass (in **\_\_\_\_\_** ) of 1 mole of the substance.

Answer 27

in _grams_

Question 28

The mass of the electron is so small that **Na⁺** and **Na** have the **\_\_\_\_\_** mass.

Answer 28

_same_ mass ## Footnote *(for this purposes)*

Question 29

The _____ mass of a substance can be obtained by summing the masses of the component atoms.

Answer 29

_molar_ mass

Question 30

In a sample, the molar mass is known in a compound. The number of _\_\_\_\_\__ present in a sample of known mass can be determined. The reverse is also true.

Answer 30

_moles_

Question 31

The **mass \_\_\_\_\_\_** is converted to mass percent by multiplying 100%

Answer 31

mass _fraction_

Question 32

The mass **\_\_\_\_\_** is the percentage of a component of a mixture or given element in a compound.

Answer 32

mass _percent_

Question 33

The **mass percent** is known as **\_\_\_\_\_** percent.

Answer 33

_weight_ percent

Question 34

In a sample, the **mass percent** of all the elements equal \_\_\_\_\_%, furthermore rounding off may produce a small deviation.

Answer 34

_100_%

Question 35

In a sample, due to **\_\_\_\_\_ \_\_\_\_\_\_**, the sum of the **mass percent** in that compound may not be exactly 100%

Answer 35

_rounding_ _off_

Question 36

In a sample, a chemist determines that a compound has been formed, where elements are present and weights are known of each. This data can be used to obtain the **\_\_\_\_\_ of the compound**.

Answer 36

_formula_ of the compound

Question 37

In a sample of an unknown compound, we determine the formula by using the _____ masses of the elements present.

Answer 37

_measured_ masses

Question 38

In a compound that is broken down into it’s separate elements and the atoms that are present are counted – what is only known is the **\_\_\_\_\_** of atoms.

Answer 38

_ratio_ of atoms

Question 39

The **\_\_\_\_\_ formula** or (simplest formula) expresses the formula of a compound, the smallest whole-number ratio of atoms present.

Answer 39

_empirical_ formula

Question 40

In simple terms, the empirical formula is the simplest **\_\_\_\_\_ _____ ratio** of atoms in a compound

Answer 40

_whole_-_number_ ratio

Question 41

The molecular formula, it is the actual formula of a compound, this formula gives the **\_\_\_\_\_\_** of the molecules that are present.

Answer 41

_composition_

Question 42

The **molecular formula** gives the exact formula of a molecule, giving the types of **\_\_\_\_\_** and the number of each type.

Answer 42

types of _atoms_

Question 43

In the **empirical formula**, when calculating, the **\_\_\_\_\_** mass (of various elements that are present) is first determined.

Answer 43

_relative_ mass

Question 44

In the empirical formula, when calculating, the relative mass (of various elements that are present) is first determined. One method of calculating this measure, it is by measuring the masses of **\_\_\_\_\_** that react to form the compound.

Answer 44

masses of _elements_

Question 45

At times, in a sample the **relative numbers of moles** obtained when calculating an **empirical formula** will contain non-integers. When this happens, the numbers must be **\_\_\_\_\_**.

Answer 45

the numbers must be _converted_

Question 46

In a sample where the composition of a compound (in terms of masses or percentages) of elements present, the calculation of the empirical formula maybe used, however what cannot be calculated is the **\_\_\_\_\_** formula.

Answer 46

_molecular_ formula

Question 47

What is the Molecular formula?

Answer 47

*(view image)*

Question 48

What is the molar mass formula?

Answer 48

*(view image)*

Question 49

What is the small whole number formula?

Answer 49

*(view image)*

Question 50

In realization, the molecular formula is always an **\_\_\_\_\_** multiple of the empirical formula.

Answer 50

_integer_

Question 51

In terms, the empirical formula, the n is an \_\_\_\_\_. If n = 1, the molecular formula is the same as the empirical formula.

Answer 51

the n is an _intiger_

Question 52

In terms, the empirical formula, the n is an integer. If n = **\_\_\_**, the molecular formula is the same as the empirical formula.

Answer 52

If n = _1_

Question 53

In objects, they do not need to have identical masses to be counted by weighting. All that needs to be known is the **\_\_\_\_\_** mass of the objects.

Answer 53

_average_ mass of the objects

Question 54

In a sample, when counting the atoms of a given element by weighing, the **\_\_\_\_\_** of the sample and **\_\_\_\_\_** mass for that element must be known.

Answer 54

the _mass_ of the sample and _average_ mass

Question 55

In a sample, where the ratio of the masses is the same as the ratio of the masses of individual atoms, they always contain the same number of **\_\_\_\_\_**.

Answer 55

_atoms_

Question 56

1 mole of anything contains **\_\_\_\_\_** units of that substance.

Answer 56

_6.022_E23_

Question 57

In a sample, an element with a mass equal to the elements average atomic mass contains exactly **\_\_\_\_\_** mole of atoms.

Answer 57

_1_ mole of atoms

Question 58

The molar mass of any compound is the **\_\_\_\_\_** in grams of 1 mole of the compound.

Answer 58

_mass_ in grams of 1 mole

Question 59

The **molar mass** of a compound is the **\_\_\_\_\_\_** of the masses of the component atoms.

Answer 59

_sum_ of the masses of the component atoms

Question 60

What is the Mass Percent Formula ?

Answer 60

(view image)

Question 61

The empirical formula of a **\_\_\_\_\_** is the simplest whole-number ratio of the atoms present in the compound.

Answer 61

empirical formula of a _compound_

Question 62

The empirical formula can be found from the **\_\_\_\_\_** composition of the compound.

Answer 62

_percent_ composition of the compound

Question 63

The molecular formula is the exact formula of the _____ present in a substance.

Answer 63

_molecules_ present in a substance

Question 64

The molecular formula is always a whole-number _\_\_\_\_\__ of the empirical formula.

Answer 64

whole-number _multiple_ of the empirical formula