NAME _____________________________NOTES: UNIT 4 (1): THE MOLE: AVOGADRO’S CONSTANT
TO GRAM FORMULA MASS (MOLE MASS)
The purpose of these next few pages is to introduce you to the current and the most likely FUTURE definition of the
mole. But first, a story...about ME!
In between my high school Regents Biology class, and my General Biology class in college, it had been agreed that the
the number of taxonomic kingdoms should be increased from 3 taxonomic Kingdoms of Animalia (Metazoa), Plantae and
Protista to 5 Kingdoms: Animalia (Metazoa), Plantae, Protista, Fungi, Monera. Since then, here in the USA, we’ve
moved up to 6 kingdoms, by splitting Monera into Archaea and Bacteria. And, some biologists advocate losing the
concept of taxonomic Kingdoms altogether! Mind you, no one consulted me on the changes....
What's the point of that story? Well, when I was your age, I didn't get that this sort of stuff could change, and I spent
the first few months of college confused, because I held tightly to what I was taught first, and since I had been really
successful with 3 Kingdoms, I didn't want to change. But, these issues do "evolve", (pun intended) ….
And I think, that by the time you get to college, the definition of “the mole” will have been changed....
You, see, the type of debates and evolutions occurring in biology are occurring in chemistry. One such debate is on
chemistry changes the definition of the Systeme Internationale (Fr) unit for the "amount of substance", or, the mole.
http://www.moleday.org/index.htm
Well, in 2014, the definition of the term, MOLE, was changed. At one point, the term mole referred to the amount of
substance of a system of chemicals which contains the same number of elementary entities as there are in 0.012 kilograms
of carbon-12.
However, in 2014, that all changed and a new definition linking the term MOLE to a number (and not a mass), was
adopted by the General Conference on Weights and Measure. The new definition for the “amount of substance” is:
“The mole, unit of amount of substance of a specified elementary entity, which may be an atom,
molecule, ion, electron, any other particle or a specified group of such particles, is such that the
Avogadro constant is equal to exactly 6.022 141 79 x 1023 per mole. http://www.iupac.org/publications/ci/2010/3201/2_lorimer.html
As a rule, when the term, mole, is used, the elementary entities must be specified and may be atoms,
molecules, ions, electrons, other particles, or specified groups of such particles. http://goldbook.iupac.org/M03980.html
217
An Introduction to the term: MOLE
The word, mole is from the Greek for "pile or heap". It was first proposed by Amedeo Avogadro, around 1811 ... and it
was immediately, pretty well ignored. It is believed that August Hortsmann coined the term, gram-molecular weight
(which is a synonym for a mole mass) in the 1880's and Wilhelm Ostwald was first to use the term, mole in 1900. The
first numerical value for the number of entities represented by 1 mole was first calculated in 1908 by Jean Baptiste
Perrin. http://rd.springer.com/article/10.1007/s10698-011-9128-7
and http://www.iupac.org/publications/ci/2010/3201/2_lorimer.html
The term mole refers to the "quantity of substance". It has the symbol of n, and the term mole, is abbreviated as mol.
(No, really, I kid you not!)
For example: You will see the symbol of “n” used in

arithmetic equations such as the Ideal Gas Law: PV = nRT

polymerization reaction equations, where “n” stands for moles of reactant as well as moles of repeating
subunits such as in the polymerization of ethene: n CH2 =CH2  [-CH2-CH2-]n

the hydrocarbon general formula: CnH2n+2. (Yep! The “n” represents moles of carbon atoms in 1 mol of
molecules of the compound….)
The term mole is analogous to terms such as: dozen, couple, few, pair, baker's dozen ...etc. It is just a number, but a big
number.
Why the Change?
Dr. Jack Lorimer, iterated the endorsed position of IUPAC, in the Jan/Feb 2010 issue of Chemistry International,
..... At its Glasgow meeting at the IUPAC General Assembly, ICTNS (International Committee
of Terminology, Nomenclature and Symbols) devoted a half-day session to this request, which
started with a presentation by Ian Mills, IUPAC’s representative on the CCU and currently
president of that body. Vigorous discussion followed, leading to conclusions that the
redefinition should be supported, and that redefining the unit should provide an excellent
opportunity to redefine the name of the base quantity at the same time. The outcome of the
session was a resolution to the Bureau:
“Given that:
(a) definition of the mole in a way that is independent of mass is desirable;
(b) the mole is often thought of by chemists as an Avogadro number of entities; and
(c) the name of the ISQ (International System of Quantities) base quantity “amount of substance”
has been a source of much confusion, ICTNS recommends to the Bureau that:
The recommendation of the CCU (Consultative Committee on Units) of the BIPM, that the mole be defined as:
“The mole, unit of amount of substance of a specified elementary entity, which may be an atom, molecule, ion,
electron, any other particle or a specified group of such particles, is such that the Avogadro constant is equal to
exactly 6.022 141 79 x 1023 per mole. http://www.iupac.org/publications/ci/2010/3201/2_lorimer.html
218
 Thus, we will essentially use the new definition and define 1 mol of a substance has a number of entities (or
species) that is equivalent to Avogadro's constant (NA).
And Avogadro’s constant, equals a large number.... and for most courses, it is simplified as, 6.022 x1023 (or just
6.02 x 1023) elementary species (atoms, molecules, ions, electrons...)
In Honors Chemistry I round to 6.02 x 1023. And, this value of 6.02 x1023 is recorded in Table C of your expanded
reference tables.
For this packet only, I will continue to use 6.022 x 1023 …only because this value works exceedingly well for some of the
“proofs” I want to use to help you learn about the mole.
For most of our math problems, we will revert to the simpler 6.02 x 1023 value, and use this value on tests/quizzes… I
think you’ll get the hang of things, using just plain ‘ol 6.02 x1023 (602 000 000 000 000 000 000 000)
READING: The reading is an adaptation of work found in Chemistry: Visualizing Matter: The Technology Edition
Myers et al. p 80-1 Holt 2000
Atomic Mass Unit & The Mole
Atoms are so small that the mass unit, gram, is inconvenient and a bit silly. Consider the idea that it would
require approximately, 1.47 x 108 atoms of oxygen, placed side-by-side to equal the “face” diameter of a U.S.
penny. In terms of mass, 1.47 x 108 atoms of oxygen equals 3.91 x 10-15 grams! (0.00000000000000391 g)
(Atoms are pretty small!)
To deal with the issue of such small values, chemists have adopted the use of a somewhat different unit to
denote the mass of atoms. This unit is called the atomic mass unit (). One  equals 1.6605402 x 10-24 grams
(0.0000000000000000000000016605402 grams).
As of 2012 the magnitude of an atomic mass unit () is equal to 1/12th of the mass of a C-12 ( 126 C ) atom. This
is noted on your NYS Periodic Table (see the Key at the top of the page)
The modern periodic table often lists the relative atomic mass of each element and the assumed unit is .
To date, our course has dealt with individual atoms. However, this becomes incredibly unproductive. Most of
chemistry is done at what might be termed, the macroscopic level and chemists find it useful to work with a
unit that represents a large collection of entities. This concept (and unit) serves as a bridge between the
invisible world of atoms and the macroscopic world of materials and objects. This concept is the mole (mol).
219
WHEN IN DOUBT, COVERT TO MOLES
Given the "body" of knowledge in chemistry ... the atom is the heart of the body, if you will allow me propound
such a metaphor. The concepts of redox and acid/base are the muscle, joints, ligaments, these account for the
"work" ... and mole theory is the brain ... helping to organize it all, or to seam it all into a whole. So, when you
don't know what to do, when given a measurement ... use your brain ... and see if you can convert the
measurement to moles ...that central, organizing, unifying concept.
Most students are said to run from the concept of the mole. However, it really boils down to one critical
attribute… That attribute is….that a mole = some calculable mass.
★★ The mole at its most fundamental level is simply a number of species of a
substance, which can be converted to a mass.
We will discuss the "quantity of substance” or the mole in terms of particles,
volume & mass … but the most important of these, for the first year student, is
mass.
You will be taught how to determine the  mole mass of any substance. Once you know the mole mass,
you can maneuver your way around any mole problem. Thus, the mole becomes the central issue of
measurement. And I re-iterate, when you are confused, stymied, or just stumped … take whatever
measurement you are given and convert it to a mole value.
http://www.orbromart.com/moleday/
WHAT ANALOGIES CAN BE USED TO IMAGINE 1 MOLE OF SOMETHING?
Think about Avogadro's number [NA ≅ 6.022 x 1023 ]
Now … in your opinion…estimation…guess-timation….
Would 1 mol of rice grains be contained, completely in a 2000 mL beaker?
Would 1 mol of rice grains be contained, completely in our classroom?
Would 1 mol of rice grains be contained in the space of this floor of classrooms?
Would 1 mol of rice grains be contained by the entire building, assuming the use of closets, rooms…etc?
220
Count Lorenzo Romano Amedeo Carlo Avogadro, di Quaregna e di Cerreto
(1776 – 1856)
A PILLAR OF THE CHEMISTRY COMMUNITY
http://fr.wikipedia.org/wiki/Amedeo_Avogadro
WELL … LET’S THINK OF THE “SIZE OF 1 MOLE LIKE THIS…



1.00 mole of rice grains would fill a cube 120. miles on each edge
1.00 mole of rice grains equals more grains than all grain grown since the beginning of time
1.00 mole of rice grains would cover all the land area in the world to a depth of 75 meters

IBM announced in 1989 that its fastest computer chip could process 6,000 mips (million instructions per sec) and
could count the entire population of the US in 4/100 second (0.04 seconds) but the same computer would require
over 3 million years to count to Avogadro's number (6.022 x 1023 = 602,200,000,000,000,000,000,000).

In order to fit 1.0 mole of raindrops into a 30. meter diameter tank, the sides of the tank would have to be 280
times higher than the distance from the earth to the sun. (The distance from the earth to the sun is approx. 93 million miles)

If 1.0 mole of pennies were divided equally between every person on earth, each person would receive 1.2 x 1014
OR…..
pennies. Personal spending, at the rate of one million dollars/day would use up each person's wealth in just under
3,000 years. However, the surface of the earth would be buried in pennies to a depth of about 420 meters.

Pretend you get a counting job, the day you learn how to count. Assume you counted by ones, eight hours per day,
five days per week for 50 weeks a year. (We'll give you 2 weeks of vacation.) If you reached five billion by the
time you retired at the age of 65, you would be considered to be a "good counter". Now, if every living person
were to count by ones from the time they learned to count, until they reached the age of 65 years old, this army
could count all of the leaves on all the trees, shrubs and bushes in the whole world in about two months.
However, all of the efforts of this same group would just about count all of the atoms of iron in the head of
a straight pin…which is nowhere near the mass of 1 mol of iron.
In order to think of 1 mole you could just go get * 18.0 grams of water.
(Do you now have an idea of how small a molecule of water is?)
Check out: http://www.wimp.com/howbig/
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Avogadro’s thinking on this issue … that there could be a means of obtaining a consistent
(equal) number of chemical species, turned on the prior work of Joseph Gay-Lussac and his
work on the volumes of gases. As Avogadro wrote…
“…it is apparent that we have the means of determining very easily the relative masses of the
molecules of substances obtainable in the gaseous state, and the relative number of these
molecules in compounds; for the ratios of the masses of the molecules are then the same as
those of the densities of the different gases at equal temperature and pressure, and the relative
number of molecules in a compound is given at once by the ratio of the volumes of the gases
that form it. For example, since the numbers 1.10359 and 0.07321 express the densities of the
two gases oxygen and hydrogen compared to that of atmospheric air as unity, and the ratio of
the two numbers consequently represents the ratio between the masses of equal volumes of
these two gases, it will also represent on our hypothesis the ratio of the masses of their
molecules. Thus the mass of the molecule of oxygen will be about 15 times that of the
molecule of hydrogen, or more exactly, as 15.074 to 1. In the same way the mass of the
molecule of nitrogen will be to that of hydrogen as 0.96913 to 0.07321, that is, as 13, or more
exactly 13.238, to 1. On the other hand, since we know that the ratio of the volumes of
hydrogen and oxygen in the formation of water is 2 to 1, it follows that water results from the
union of each molecule of oxygen with two molecules of hydrogen.
Amedeo Avogadro Essay on a Manner of Determining the Relative Masses of the Elementary Molecules of
Bodies, and the Proportions in Which They Enter into These Compounds Journal de Physique 73, 58-76
(1811) [Alembic Club Reprint No. 4] from: http://web.lemoyne.edu/~giunta/avogadro.html
****************************
Or… to translate: Using the ideas of volume (the concept of using mass, came in the
early 1900’s) … if, for example you want to make water from dihydrogen and dioxygen
and wanted no gas left over when you’re done, you would have had to use exactly twice the
volume of dihydrogen gas as you did dioxygen. From that Avogadro deduced that
assuming the same temperature and pressure, equal volumes of gases have equal
numbers of molecules. When you fill one balloon with oxygen, and another with hydrogen,
and another with methane (for instance), as long as the volumes, temperature and pressure
are the same each balloon will have the same number of molecules in it.
222
I) MOLE (abbreviation = mol) [Greek = heap] We may speak of the mole in at least three ways:
1 mol
equals
a # of grams
a # of particles
called
the volume of 1 mol of gas (a # of liters [gaseous volume])
called
mole mass
Avogadro's constant
A different calculation
called
molar volume
6.02(2) x 1023
22.4 L
for each substance.
Calculated using the
a constant
chemical formula and
values from the periodic table
table
All Chemistry
used only for gases @ STP
according to KMT gases exist as molecules
a constant number for ideal gases
Honors Level
Honors Level
A) Definition: Technically, 1 mol is the SI base unit for the quantity of substance. Remember, when the mole
is used, the elementary entities must be specified and may be atoms, molecules, ions,
electrons, other particles, or specified groups of such particles. (http://goldbook.iupac.org/M03980.html)
1) Species:
* molecules
= descriptor for substances made from atoms chemically united via covalent bonds
(this applies to covalent compounds and a few elements e.g.) diatomic elements)
* formula units
= species for ionic compounds
* atoms
= species for most elements
* ions
= species for the products of
dissolved / dissociated ionic compounds
... up to 6.02 x 1023
2) mass in grams totaling 6.02(2) x 1023 molecules or formula units or atoms
3) volume in Liters
http://www.gluegrant.org/burnresearch.htm
22.4 Liters
containing
6.02(2) x 1023
molecules @
STP
223
II) The Mole
A) The MOLE is related to Avogadro's constant (NA) ….
1) As with other terms, such as dozen, couple, few... the term mole simply represents a number.
a) 1 mole = 6.02(2) x 1023
b) 6.02(2) x 1023 molecules is used when working with molecular (covalent) materials
issue of
vocabulary only
6.02(2) x 1023 formula units is used when working with ionic compounds
6.02(2) x 1023 atoms used when working with most elements (exceptions: e.g. diatomic elements)
0.5 mol = 3.01 x 1023
1 mol = 6.022 x 1023 molecules /formula units/ atoms
1.5 mol = 9.03 x 1023
2 mol = 1.2044 x 10 24
What's up with this exponent being 24 and not 23?
B) The MOLE as a volume
1) applies only to gaseous volumes assuming STP conditions
2) 1 mol of gas at STP = 22.4 L
0.5 mol = 11.2 L
1 mol = 22.4L
1.5 mol = 33.6 L
2 mol = 44.8 L
-1
C) The MOLE as a MASS (grams/mol or g•mol )
Mole Mass
(BEST TERM: can't go wrong using this phrase although there are other names...)
the number of grams in 1 mol of a substance (element or compound)
calculated using values off the
PT and the formula of the substance
one name
Gram Atomic Mass
(used for most elements)
another name
Gram Formula Mass
(used when speaking of compounds)
EXCEPT the 7-H club
abbreviation
GAM (elements)
abbreviated as
GFM (compounds & diatomics)
0.5 mol = ½x
1 mol = x grams
1.5 mol = 1.5x
2 mol = 2x
One mole mass of a substance has (approximately) 6.02(2) x 1023 species of that substance.
224
1) Definition: Gram Atomic Mass (GAM) * The mass, in grams of 1 mol of atoms of an element
a) to determine: Look up the relative atomic mass and give that
number a unit of “grams”.
22.98977
b) Record the GAM of each element, as listed on the Periodic Table
but rounded to the nearest whole number.
S ________
Mg _________
H _________
Cl ________
Cu __________
Au ________
+1
Na
11
2-8-1
c) 1 GAM is a mass that represents 6.02(2) x 1023 atoms of most elements 
1 GAM of an element represents 1 mol of the element
2) Gram Formula Mass (GFM) * The mass of 1 mol of a diatomic element or any compound
a) to determine: Multiply each element’s GAM by its subscript from the formula and add the
products of each element together.
b) Calculate the GFM of C2H5Cl
Calculate the GFM of Al(NO3)3
12.0111
C
1.00794
H
35.453
Cl
Note: This helps you to understand what the ( ) around
a polyatomic ion imply. Learn this!!!
26.98154
Al
14.0067
15.9994
N
O
Calculate the GFM of Mg3(PO4)2
Remember: One mole mass (one GAM or one GFM) of a substance has (approximately) 6.02(2) x 1023 species
(atoms, molecules, formula units ….) of that substance.
225
Comprehension about the mole and mole mass
If you read: GAM or GFM in a problem, then you should think of * 1 mole mass
The mass of 1 mol mass of a substance is calculated by using * the atomic mass from the periodic table
and the subscript of each element from the chemical formula and add up the products
1 mole mass represents * 6.02 x 1023
molecules (for covalent) or formula units (for ionic cmp)
1 mole mass of any ideal gas at STP equals a volume equal to * 22.4
Liters
1 mole mass of a diatomic element is twice the value of the * atomic mass of the Per. Table, in grams
The subscripts outside the ( ) of a polyatomic ion * applies to every species inside the ( )
Directions: This is just a "drill" exercise regarding the calculation of a mole mass. Use your Periodic Tables to
calculate the mole mass of each substance. For this exercise, use the GAM rounded to a whole-number
1. Calculate the GFM of SF6
a)
b)
c)
d)
51 grams
146 grams
231 grams
25 grams
2) Calculate the mole mass of N2.
a) 14 grams
b) 56 grams
c) 28 grams
d) 43 grams
3) Calculate the GFM of Al2O3
a)
b)
c)
d)
102 grams
114 grams
73 grams
79 grams
4) What is 1 mole mass (the GAM) of
chromium metal?
a)
b)
c)
d)
can not be determined
24 grams
52 grams
18 grams
5) Calculate the mole mass of SiO2.
a) 60 g
b) 91 g
c) 26 g
d) 32 g
6) Calculate the GFM of Na2Cr2O7.
a) 262 grams
b) 507 grams
c) 82 grams
d) 117 grams
7) Calculate the GFM of Ca(NO3)2
a) 180 g
b) 164 g
c) 147 g
d) 23 g
8) Calculate 1 gram formula mass of Ca3(PO4)2.
a) 133 g
b) 49 g
c) 151 g
d) 310 g
226
9) What is the GFM of Al2(CrO4)3 ?
a) 402 g
b) 210 g
c) 197 g
d) 445 g
17) Calculate the mass of 0.50 mole of H2O.
a) 18 grams
b) 5.0 grams
c) 72 grams
d) 9.0 grams
10) Calculate the GFM of C8H18
a) 66 grams
b) 1,728 grams
c) 114 grams
d) 37 grams
18) Calculate the mass of 2.50 moles of NaCl mass.
a) 145 grams
b) 57 grams
c) 309 grams
d) 75 grams
11) Calculate the GFM of Fe2(S2O3)3
a) 448 grams
b) 932 grams
c) 506 grams
d) 774 grams
12) Calculate the GFM of NH4Cl
a) 53 grams
b) 3 grams
c) 104 grams
d) 92 grams
SELECTED ANS. 1) b
7) b
2) c 3) a
8) d 12) a 13) d
4) c
6) a
15) d 18) a
13) Calculate the GFM of F2.
a) 9.0 grams
b) 18 grams
c) 19 grams
d) 38 grams
14) Calculate the GFM of MgO
a) 20 grams
b) 40 grams
c) 384 grams
d) 77 grams
15) Calculate the GFM of C6H12O6.
a) 342 g
b) 201 g
c) 299 g
d) 180 g
16) Calculate the mass of 3.0 moles of H2O.
a) 18 grams
b) 36 grams
c) 54 grams
d) 90 grams
227
Why is the value of 1 mole equal to 6.02(2) x 1023?
Really, no matter which definition we use, we keep coming back to
Avogadro’s constant of: 6.02(2) x 1023.
What’s-up with that? I mean, why isn’t the “constant” 4.11 x 107 or
1.877 x 1040 ?
Well, 6.02(2) x 1023 is NOT some random value. It’s connected to
atomic structure!!!
Some of the scientists whose breakthroughs
contributed to the modern definition of the
mole. (from left): Lord Kelvin, Johann Josef
Loschmidt, Amedeo Avogadro, & Stanislao
Cannizzaro. (http://tinyurl.com/c8a5zua)
Recall that the unified atomic mass unit = 1/12 the mass of a C-12 atom or rather: 1/12 of (12.00000) = 1 μ
& that, 1 μ = 1.66053 x 10-24 gram. This is based on experimental work in the late 19th to early 20th century.
Essentially, the value of the mole is all about the relationship between the unified atomic mass unit and the
unit of gram.
Or, as Cate Devey (Class of 2013) realized … all on her own, you simply need to ask:
How many atomic mass units (μ) are equivalent to 1.00 gram of matter? All you need to do is, divide.
1.00 gram
= 6.022 x 1023.
-24
1.66053 x 10 gram
COOL, HUH?! ... talk about a gemstone winner!
Now, this relationship (value) keeps turning up over and over again, especially when we assume that one molar
mass is the numerical equivalent of the relative atomic mass, but with the unit of grams.
Example: Sodium (Na):
The relative atomic mass of sodium is approximately 22.9μ
1) convert μ to grams: g = 22.99 μ |1.66053 x 10-24 grams | = 3.818 x 10-23 grams per 1 atom of Na
1μ
2) Assume 22.99 grams of Na equals 1 mole mass and ask “How many atoms of sodium metal are
equal to 3.818x 10-23 g atoms
# of atom = 22.99 grams of Na | 1 atom
|
= 6.021 x 1023 atoms! Close enough!!!
-23
3.818 x 10 gram
3) This can be repeated over and over. Convert the relative atomic mass for 1 atom from μ to grams
…then assume a gram value of that relative atomic mass and divide by the mass of 1 atom in grams.
228
NAME ________________________________
A BIT OF PRACTICE INTERPRETING THE BASICS OF
AVOGADRO’S CONSTANT
DIRECTIONS: Use your grasp of the last few classes, to complete each of the following questions. Be sure to provide the most
correct response to each question …
But more importantly, in order drive home the conceptual development of the mole … please reflect on why
you are answering the way you answer … and develop the reasoning you can use consistently to
explain/defend/predict your current and future responses. Get those “because” statements in order…
Okay?
___1) How many moles of carbon atoms are contained in 1 mol of hexane molecules (C6H14)?
___2) How many moles of carbon atoms are contained in 5 mol C6H14 molecules … (or 5 C6H14 ) ?
___3) How does the role of the coefficient differ from the role of a subscript, in terms of determining the
number of mols of a substance?
____________________________________________________________________________
_____________________________________________________________________________
_____________________________________________________________________________
___4) How many moles of nitrogen atoms are contained in 1 mol of Al(NO3)3?
___5) How many moles of nitrogen atoms are contained in 7 Al(NO3)3 ….[that’s 7 moles of aluminum nitrate]?
___6) How many moles of nitrogen atoms are contained in 0.50 mol of Al(NO3)3 ?
Hopefully, you will notice with 4-7,
that a question about a specific element, could be asked with a number of slightly different formats …be flexible with your interpretations)
___7) Calculate the number of mol of neutrons in 0.50 mol of 56
26Fe atoms
__________8) What is the total number of neutrons (as opposed to mols of neutrons) in 0.50 mol of
Put your response in proper scientific notation, please. (Note how question 8 differs from 7)
56
26Fe
atoms?
____________ 9) How many molecules are there in 1 mol of C4H9COOH (butanoic acid)?
_______10) How many moles of atoms are there in 1 mol of C4H9COOH (butanoic acid)?
229
11) Assume 1 atom of calcium (Ca0) masses out at 6.65 x 10-23 grams. Calculate the number of calcium atoms
found to exist in 40.08 grams of the metal? Show your work, using dimensional analysis.
12) Assume 1 atomic mass unit equals 1.66053 x 10-24 grams. Assume 1 atom of aluminum masses out at
26.98 𝜇. How many grams of aluminum are required to equal a given of 6.022 x1023 atoms of aluminum?
Show your work, using dimensional analysis.
*grams Al = 6.022 x 1023 atoms Al| 26.98𝜇 | 1.66053 x 10-24 grams |
1 atom
1𝜇
Answers:
1) 6 mol of C atoms: the subscript can be used to indicate the moles of atoms of a specific element of a compound
2) 30 moles of C atoms: multiply the total moles of compound by the individual subscript
3) Answers may vary … but consider that the subscript is applied to a specific element, while the coefficient applies to
each species of an entire substance.
4) 3 mol of nitrogen atoms: Al(NO3)3
5) 21 mol of nitrogen atoms
6) 1.5 mol of nitrogen atoms
7) 15 mol of neutrons …Ask… How many neutrons are in 1 atom of Fe-56? There are 30 neutrons in 1 atom of Fe-56
Well, then how many moles of neutrons would then be in 1 mol of Fe-56 atoms? Well, there would be 30 mols.
Hence, how many moles of neutrons would be in only 0.50 moles of atoms?
8) 9.03 x 1024 neutrons
9) 6.02 x 1023 molecules or 1 moles worth of molecules or a number of molecules equal to Avogadro’s constant
10) 17 moles of atoms
11) 6.02 x 1023 atoms
12) 26.98 grams of calcium
NOTICE HOW EACH OF THE ANSWERS ADDRESSES THE SPECIES … ATOMS, MOLECULES,
NEUTRONS … THIS IS A VERY IMPORTANT POINT. THE SPECIES MUST BE IDENTIFIED….
230