Name:
Date:
The Mole Web-quest
Use the following website to answer this set of questions:
http://antoine.frostburg.edu/chem/senese/101/moles/faq/why-use-moles.shtml
1) A mole of anything is how many? (give the number):
2) Why is it that different amounts of things can still equal one mole? (think about the
weight of a dozen elephants vs a dozen eggs)
3) Why do we want to use the concept of moles?
4) Once we know the number of moles we can convert to the number of:
____________________ or ______________________ and vice versa.
5) How many grams of water are in one mole of water?
6) How many molecules of water are in one mole of water?
Use the following website to answer the next set of questions:
http://chemistry.about.com/od/workedchemistryproblems/a/molegramconvert.htm
7) What is the formula for the atomic weight (weight of one mole) of CO2 ?
8) What is the formula used to go from 454 grams of CO2 to moles of CO2? How many
moles do you get?
9) NOW YOU TRY (not on the website)
a. What is the atomic weight of one mole of CH4?
b. How many moles in 64 grams of CH4?
10)What is the formula to determine the mass in grams of 3.6 moles of H2SO4?
11)NOW YOU TRY (not on website)
a. What is the mass in grams of 4.2 moles of FeO2?
Use the following website to answer the next set of questions:
http://misterguch.brinkster.net/molecalculations.html
Scroll down to “solving a 2 part chemistry problem”
12) What are the steps needed to convert 22 grams of copper to atoms of copper. Please write
them out (include the chart we did in class)
13) NOW YOU TRY: How many atoms are there in 34 grams of Lithium? Show your
work!!!!!!!
Go to the bottom of this document and read all about “Amadeo Avagadro” to answer the
next set of questions:
14) What is Avogadro’s full name?
15) Originally, what profession was Avogadro?
16) In 1811 Avogadro wrote a paper that clearly distinguished a _____________ from a
_____________.
17) What is Avogadro’s Principle?
18) List one crazy fact about Avogadro’s number.
All the information you have found so far has come from various websites. So what makes a
source good or bad? Read the following pages and answer the questions that follow.
Amedeo Avogadro
Avogadro - the man
Lorenzo Romano Amedeo Carlo Avogadro, conte di Quaregna e di Cerreto
(1776 - 1856), was born in Turin, Italy, on 9th August, 1776. He was the son of
Count Filippo Avogadro and Anna Maria Vercellone. His father was a
distinguished lawyer and civil servant, becoming a senator of Piedmont in 1768,
and was appointed advocate general to the senate of Vittorio Amedeo III in 1777.
Under the French rule of 1799 he was made president of the senate.
Amedeo Avogadro went to school in Turin. Coming from a family of well
established ecclesiastical lawyers, Avogadro was guided toward a legal career, and
became a bachelor of jurisprudence in 1792, at the ripe old age of just 16 years.
Four years later he gained his doctorate in ecclesiastical law and began to practice.
In 1801 he was appointed secretary to the prefecture of the department of Eridano.
In spite of his successful legal career, Avogadro also showed an interest in natural
philosophy, and in 1800 he began private studies of mathematics and physics. His
first scientific research in 1803, undertaken jointly with his brother Felice, was on
electricity.
In 1806, Avogadro was appointed demonstrator at the Academy of Turin, and in
1809 became professor of natural philosophy at the college of Vercelli. In 1820,
when the very first chair of mathematical physics in Italy was established at the
University of Turin, Avogadro was appointed. Unfortunately, his post was short
lived, since political changes suppressed the chair and Avogadro was out of a job by
July, 1822. The chair was eventually reestablished in 1832, and Avogadro was
reappointed to the position in 1834. Here he remained until his retirement in 1850.
Avogadro had succeeded to his father's title in 1787. He married Felicita Mazzé,
and they had a total of six children. Avogadro led an industrious life, and was a
modest man, working in isolation. This probably contributed to his relative
obscurity, particularly outside Italy. Avogadro died on the 9th July, 1856. He was
described as religious, but not a bigot.
Avogadro - his contribution to chemistry
In order to understand the contribution that Avogadro made, we must consider some
of the ideas being developed at this time. Chemistry was just beginning to become
an exact science. The Law of Definite Proportions and the Law of Multiple
Proportions were well accepted by 1808, at which time John Dalton published his
New System of Chemical Philosophy.
Dalton proposed that the atoms of each element had a characteristic atomic weight,
and that it was atoms that were the combining units in chemical reactions. Dalton
had no method of measuring atomic weights unambiguously, so made the incorrect
assumption that in the most common compound between two elements, there was
one atom of each.
At around this time, Gay-Lussac was studying the chemical reactions of gases, and
found that the ratios of volumes of the reacting gases were small integer numbers.
This provided a more logical method of assigning atomic weights. Gay-Lussac did
not carry through the full implications of his work. However, Dalton realized that a
simple integral relation between volumes of reacting gases implied an equally
simple relation between reacting particles. Dalton still equated particles with atoms,
and could not accept how one particle of oxygen could yield two particles of water.
This was a direct threat to the relatively new atomic theory, and therefore Dalton
tried to discredit the work of Gay-Lussac.
In 1811, Avogadro published an article in Journal de physique that clearly drew the
distinction between the molecule and the atom. He pointed out that Dalton had
confused the concepts of atoms and molecules. The "atoms" of nitrogen and oxygen
are in reality "molecules" containing two atoms each. Thus two molecules of
hydrogen can combine with one molecule of oxygen to produce two molecules of
water.
Avogadro suggested that equal volumes of all gases at the same temperature and
pressure contain the same number of molecules which is now known as Avogadro's
Principle.
The work of Avogadro was almost completely neglected until it was forcefully
presented by Stanislao Cannizarro at the Karlsruhe Conference in 1860. He
showed that Avogadro's Principle could be used to determine not only molar
masses, but also, indirectly, atomic masses. The reason for the earlier neglect of
Avogadro's work was probably the deeply rooted conviction that chemical
combination occurred by virtue of an affinity between unlike elements. After the
electrical discoveries of Galvani and Volta, this affinity was generally ascribed to
the attraction between unlike charges. The idea that two identical atoms of
hydrogen might combine into the compound molecular hydrogen was abhorrent to
the chemical philosophy of the early nineteenth century.
Avogadro - his number
It was long after Avogadro that the idea of a mole was introduced. Since a
molecular weight in grams (mole) of any substance contains the same number of
molecules, then according to Avogadro's Principle, the molar volumes of all gases
should be the same. The number of molecules in one mole is now called
Avogadro's number. It must be emphasized that Avogadro, of course, had no
knowledge of moles, or of the number that was to bear his name. Thus the number
was never actually determined by Avogadro himself.
As we all know today, Avogadro's number is very large, the presently accepted
value being 6.0221367 x 1023. The size of such a number is extremely difficult to
comprehend. There are many awe-inspiring illustrations to help visualize the
enormous size of this number. For example:
• An Avogadro's number of standard soft drink cans would cover the surface of the
earth to a depth of over 200 miles.
• If you had Avogadro's number of unpopped popcorn kernels, and spread them
across the United States of America, the country would be covered in popcorn
to a depth of over 9 miles.
• If we were able to count atoms at the rate of 10 million per second, it would take
about 2 billion years to count the atoms in one mole.
Determination of the number
Cannizarro, around 1860, used Avogadro's ideas to obtain a set of atomic weights,
based upon oxygen having an atomic weight of 16. In 1865, Loschmidt used a
combination of liquid density, gaseous viscosity, and the kinetic theory of gases, to
establish roughly the size of molecules, and hence the number of molecules in 1 cm3
of gas.
During the latter part of the nineteenth century, it was possible to obtain reasonable
estimates for Avogadro's number from sedimentation measurements of colloidal
particles. Into the twentieth century, then Mullikan's oil drop experiment gave much
better values, and was used for many years.
A more modern method is to calculate the Avogadro number from the density of a
crystal, the relative atomic mass, and the unit cell length, determined from x-ray
methods. To be useful for this purpose, the crystal must be free of defects. Very
accurate values of these quantities for silicon have been measured at the National
Institute for Standards and Technology (NIST).
To use this approach, it is necessary to have accurate values of atomic weights,
often obtained by measuring the mass of atomic ions. For example, an ion trap,
employing extremely uniform and stable magnetic and electric fields should allow
such measurements to be made to better than 1 part in 1010. The relative atomic
mass of silicon is particularly important, since silicon crystals are used in the x-ray
methods mentioned above.
As a continuation of this approach, one of the 1999 NIST Precision Measurement
Grants was awarded to David Pritchard, physics professor at the Massachusetts
Institute of Technology. He will conduct cyclotron frequency measurements on ions
that could achieve a 100-fold improvement in the accuracy of atomic mass
measurements. MIT has developed the world's most accurate mass spectrometer
capable of measuring the atomic mass of atoms to one part in 10 billion. Pritchard
proposes to simultaneously measure the cyclotron frequencies of two different ions
in order to improve the values of several fundamental constants, including
Avogadro's number.
At the present time, information on Avogadro's number from many different
experiments is pooled with other observations on other physical constants. A most
probable and self-consistent set of physical constants that best fits all reliable data is
then found by statistical methods.
The size of Avogadro's number is determined by our definition of the mole. What it
does demonstrate is how small an atom or molecule is compared to the amounts of
material we are familiar with in everyday life, since the definition of the mole
involves amounts of material we are completely familiar with.