A_-_102_F11_Notes

578gsampleofpuretinsnistreatedwithgaseousfluorineuntil

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“Per
centum”
 • means
per
100
of
something
 • Percent
composition
can
be
given
in
terms
of
mass
(sometimes
“weight”
is
used),
 volume,
mols,
etc
 • To
use
this
information,
convert
the
percentage
into
a
fraction
or
ratio
 • A
compound
that
is
7.2
mol%
C
could
also
be
written
as
 mols C 
 mols compound 
 
 Question
A4
 € A
fertilizer
contains
21%
nitrogen
by
mass.

What
mass
of
this
fertilizer,
in
kilograms,
is
 needed
for
an
application
requiring
225
g
of
nitrogen?
 
 
 Avogadro’s
Number
 • The
number
of
carbon
atoms
in
exactly
12.0
g
of
12C
is
called
Avogadro’s
number
(NA).

 
 
 NA
=
6.022
x
1023
 • The
mole
is
a
measurement
of
quantity:
 
 
 1
___‐mol
=
6.022
x
1023
units
 
 
 Molar
Mass
 • Molar
Mass
is
the
mass
of
one
mol
of
a
substance

 • 6.022
x
1023
atoms
(1
mol)
of
C
weigh
12
g
and
therefore
molar
mass
of
C
is
12
g/mol.
 • 1
g‐mol
of
C
=
12
g
of
C
 • 1
lb‐mol
of
C
=
12
lb
of
C
 ChE102
Fall
2011
Class
Notes
‐
Introduction
 A ‐5 
 Question
A5
 Determine
the
name
of
the
mystery
element
if
a
2.80
x
1022
atom
sample
of
the
element
 has
a
mass
of
5.23g.
 
 
 Molar
Mass
of
Compounds
 • Calculated
from
the
molecular
formula
 • For
example:
Water
(H2O)
 • The
molar
mass
of
H
is
1
g/mol
and
O
is
16
g/mol
 • 



 • Therefore,
the
molar
mass
of
H2O
is
18
g/mol


 
 
 Question
A6
 You
work
for
a
copper
mining
company
and
are
trying
to
decide
which
mine
to
buy.

One
 mine
is
rich
in
chalcolite
(Cu2S)
and
the
other
is
rich
in
Athabascaite
(Cu5Se4).

How
 much
more
copper
(in
g)
can
be
extracted
from
the
chalcolite‐containing
mine
per
kg
of
 mineral?
 
 Composition
of
Compounds
 • Calculating
percent
composition
 • Determining
empirical
formulas
for
new
compounds
using
combustion
analysis
 • Based
on
the
knowledge
of
the
products
made
when
a
substance
is
burned
(...
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