Stoichiometry:

1

• Stoichiometry
• Mathematics of
• chemical formulas
• and equations

2
Mole
mole (mol) 602000000000000000000000

• A mole is just a number
• pair 2
• trio 3
• quartet 4
• dozen 12
• bakers dozen 13
• gross 144

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The Mole

• 1 dozen cookies 12 cookies
• 1 mole of cookies 6.02 X 1023 cookies
• 1 dozen cars 12 cars
• 1 mole of cars 6.02 X 1023 cars
• 1 dozen Al atoms 12 Al atoms
• 1 mole of Al atoms 6.02 X 1023 atoms
• Note that the NUMBER is always the same, but the
  MASS is very different!
• Mole is abbreviated mol (gee, thats a lot
  quicker to write, huh?)

4

• 1 mole is the amount of substance that contains
  as many particles (atoms or molecules) as there
  are in 12.0 g of C-12.

5
??? (Mole,Mol) ??? ?????????????????????????????
??????????????????????????????????????????????
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Amadeo Avogadro(1776 1856)
Particles in a Mole
Amedeo Avogadro (1766-1856) never knew his own
number it was named in his honor by a French
scientist in 1909. its value was first estimated
by Josef Loschmidt, an Austrian chemistry
teacher, in 1895.
?
quadrillions
thousands
billions
trillions
millions

• 1 mole 602213673600000000000000
• or 6.022 x 1023

There is Avogadro's number of particles in a mole
of any substance.
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Avogadro,s number

• A MOLE of any substance contains as many
  elementary units (atoms and molecules) as the
  number of atoms in 12 g of the isotope of
  carbon-12.
• This number is called AVOGADROs number NA
  6.02 x 1023 particles/mol
• The mass of one mole of a substance is called
  MOLAR MASS symbolized by MM
• Units of MM are g/mol
• Examples
• H2 hydrogen 2.02 g/mol
• He helium 4.0 g/mol
• N2 nitrogen 28.0 g/mol
• O2 oxygen 32.0 g/mol
• CO2 carbon dioxide 44.0 g/mol

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Mole
??? ??????? ????????????????????????????????????
????????????????-12 ???????? 12 ????
1. ?????????????????

• C-12 1 ????? ????? 12 x 1.66 x 10-24 g
• C-12 ??? 12 x 1.66 x 10-24 g ???????????? 1
  atom
• C-12 ??? 12 ???? ???????????? C-12 1 atom ?
  C-12 12 g
• 
  C-12 12 x 1.66 x 10-24 g
• 
  6.022137 x 1023 atom

1 mole 6.02 x 1023 ??????
Avogadro,s number
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Avogadros Number
6.02 X 1023
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Mole

• ????????????????? ???????? ???????? ????
  ???????
• (Zn) 1 ??????????????????????????? 6.02 x
  1023
• ?????

• ??????????????????? ???????? ?????????? ????
  ???????????? (H2) 1 ????????????????????????????
  ??? 6.02 x 1023 ???????

• ?????????????????????? ???????? ?????????????
  1 ????????????? ??????? ??????????????????????
  6.02 x 1023 ??????????

• ????????????????? ???????? ???????? ????
  ????????????? (Ca2) 1 ????????????????????????
  ??? 6.02 x 1023 ?????

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A Mole of Particles Contains 6.02 x 1023
particles

• 6.02 x 1023 C atoms
• 6.02 x 1023 H2O molecules
• 6.02 x 1023 NaCl molecules
• (technically, ionics are compounds not molecules
  so they are called formula units)
• 6.02 x 1023 Na ions and
• 6.02 x 1023 Cl ions

1 mole C 1 mole H2O 1 mole NaCl
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Avogadros Number as Conversion Factor

• 6.02 x 1023 particles
• 1 mole
• or
• 1 mole
• 6.02 x 1023 particles
• Note that a particle could be an atom OR a
  molecule!

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Learning Check

• 1. Number of atoms in 0.500 mole of Al
• a) 500 Al atoms
• b) 6.02 x 1023 Al atoms
• c) 3.01 x 1023 Al atoms
• 2.Number of moles of S in 1.8 x 1024 S atoms
• a) 1.0 mole S atoms
• b) 3.0 mole S atoms
• c) 1.1 x 1048 mole S atoms

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• 3. ??????????????????????????
• ??????? 12.04 x 1022 atom
• ????????????? 3.01 x 1025 molecule
• ??????? 3.612 x 1020 atom
• ?????????? 1 atom
• ???????????? 20 ion

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• If you had a mole of H2O could you swim in it?
• NO!
• Water molecules are so small
• that a mole of H2O 18 ml

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How small are atoms?

• There are more atoms in one gram of salt than
  grains of sand on all the beaches of all the
  oceans in all the world.

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Gram ATOMic Mass

• mass in grams of 1 mole of atoms of an element
• In other words
• 1 mol C atoms 6.02 x 10 23 C atoms 12g C

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PracticeRemember . . .1 mole 6.02x1023 atoms
or molecules ______ g from the periodic table
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Mole
2. ????????????????????
???????-12 ?????? 1 ??? ????? 12 ????
????????????????? ?????????

• ??????? ??????????? 6.02 x 1023 atom ???? 1 ???
  ?????????????????????????????????????????
• ?????? ??????????? 6.02 x 1023 molecule ???? 1
  ??? ??????????????????????????????????????????
• ???????? ??????????? 6.02 x 1023 ion ???? 1 ???
  ?????????????????????????????????????????

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Conversion Factor

• Atomic Mass (g)
• 1 mole
• or
• 1 mole
• Atomic Mass (g)

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Conversion Factor

• Molecular Mass (g)
• 1 mole
• or
• 1 mole
• Molecular Mass (g)

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• 1. ??????????????????????????
• ??? 0.36 g
• ?????????????????? 38.06 g
• ??????????? 2.70 g
• ?????? 12 g

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• 2. ??????????????????????????
• ??????? 12.04 x 1022 atom
• ????????????? 3.01 x 1025 molecule
• ??????? 3.612 x 1020 atom
• ?????????? 1 atom
• ???????????? 20 ion

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Stoichiometry of Chemical Formulas
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Gram Formula Mass Gram Molecular Mass Molar Mass

• mass in grams of 1 mole of a substance
• In other words . . . Add it all up!
• 1 mole of NaCl 58g 6.02x1023 particles of
  NaCl
• 1 mole of H2O 18g 6.02x1023 molecules of H20

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Now..

• Use the gram formula mass and the gram
  atomic mass to determine
• how many moles or atoms of an element are found
  in some mass of a substance
• how much mass that element contributes to the
  mass of the entire substance
• Use factor label follow the units!

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Stoichiometry of Chemical Formulas

• If you have 1 molecule of (NH4)2SO4
• How many atoms of N are there?
• How many atoms of H?
• SO..
• If you have 1 mole of of (NH4)2SO4
• How many moles of N are there?
• How many moles of H?

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Molar Volume
Gases ONLY _at_STP

• 1 mole of any gas
• O2 (g)
• NH3 (g)
• He (g)
• contains 6.02 x 1023 molecules and
• occupies a volume of 22.4L

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• STP
• standard temperature pressure
• 0oC or 273K

101.3kPa or 1 atm
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Remember . . .

• Gases also have mass
• 1 mole of O2(g) 32g
• 1 mole of NH3(g) 17g
• ? we can calculate Density!

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D m/v

• A sample of oxygen contains 3 moles of particles
  at STP what is its density?
• 2 steps
• Convert moles to mass AND volume
• Calculate density
• If mass or volume is given, use it and convert
  the other. THEN calculate D!

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Remember . . . 1 mole 6.02x1023 atoms or
molecules gfm 22.4L (g)
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Mole
3. ?????????????????????????
???????? ???????? 0 ???????????? ?????????? 1
???????? ??????????????? (Standard Temperature
and Pressure) ?????????????? STP
??????? 1 ??? ????????? 22.4 ????????????????
( dm3 ) ??? STP ?????????????????????????? ?
??????? 22.4 dm3 ???? 22.4 ???? ??? STP
Ex. ????????????????????????????????????
??????? 5.6 dm3 ??? STP
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Conversion Factor

• 22.4 dm3 gas
• 1 mole
• or
• 1 mole
• 22.4 dm3 gas

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1 mole
36
??????????????????????????? ??????
????????????????????
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1 Mole of Particles
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A Mole of Particles Contains 6.02 x 1023
particles

• 6.02 x 1023 C atoms
• 6.02 x 1023 H2O molecules
• 6.02 x 1023 NaCl molecules
• (technically, ionics are compounds not molecules
  so they are called formula units)
• 6.02 x 1023 Na ions and
• 6.02 x 1023 Cl ions

1 mole C 1 mole H2O 1 mole NaCl
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Molar Mass

• The Mass of 1 mole (in grams)
• Equal to the numerical value of the average
  atomic mass (get from periodic table)
• 1 mole of C atoms 12.0 g
• 1 mole of Mg atoms 24.3 g
• 1 mole of Cu atoms 63.5 g

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Other Names Related to Molar Mass

• Molecular Mass/Molecular Weight If you have a
  single molecule, mass is measured in amus
  instead of grams. But, the molecular mass/weight
  is the same numerical value as 1 mole of
  molecules. Only the units are different. (This
  is the beauty of Avogadros Number!)
• Formula Mass/Formula Weight Same goes for
  compounds. But again, the numerical value is the
  same. Only the units are different.
• THE POINT You may hear all of these terms which
  mean the SAME NUMBER just different units

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Learning Check!

• Find the molar mass (usually we round to the
  tenths place)

79.9 g/mole

1. 1 mole of Br atoms
2. 1 mole of Sn atoms

118.7 g/mole
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Molar Mass of Molecules and Compounds

• Mass in grams of 1 mole equal numerically to the
  sum of the atomic masses
• 1 mole of CaCl2 111.1 g/mol
• 1 mole Ca x 40.1 g/mol
• 2 moles Cl x 35.5 g/mol 111.1 g/mol CaCl2
• 1 mole of N2O4 92.0 g/mol

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Learning Check!

• Molar Mass of K2O ? Grams/mole
• B. Molar Mass of antacid Al(OH)3 ? Grams/mole

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Learning Check

• Prozac, C17H18F3NO, is a widely used
  antidepressant that inhibits the uptake of
  serotonin by the brain. Find its molar mass.

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Calculations with Molar Mass

• molar mass
• Grams Moles

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Converting Moles and Grams

• Aluminum is often used for the structure of
  light-weight bicycle frames. How many grams of
  Al are in 3.00 moles of Al?
• 3.00 moles Al ? g Al

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• 1. Molar mass of Al 1 mole Al 27.0 g Al
• 2. Conversion factors for Al
• 27.0g Al or 1 mol Al
• 1 mol Al 27.0 g Al
• 3. Setup 3.00 moles Al x 27.0 g Al
• 1 mole Al
• Answer 81.0 g Al

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Learning Check!

• The artificial sweetener aspartame
  (Nutra-Sweet) formula C14H18N2O5 is used to
  sweeten diet foods, coffee and soft drinks. How
  many moles of aspartame are present in 225 g of
  aspartame?

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Atoms/Molecules and Grams

• Since 6.02 X 1023 particles 1 mole AND1
  mole molar mass (grams)
• You can convert atoms/molecules to moles and then
  moles to grams! (Two step process)
• You cant go directly from atoms to grams!!!! You
  MUST go thru MOLES.
• Thats like asking 2 dozen cookies weigh how many
  ounces if 1 cookie weighs 4 oz? You have to
  convert to dozen first!

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Calculations

• molar mass
  Avogadros number Grams
  Moles particles
• Everything must go through Moles!!!

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Atoms/Molecules and Grams

• How many atoms of Cu are present in 35.4 g of Cu?

35.4 g Cu 1 mol Cu 6.02 X 1023 atoms
Cu 63.5 g Cu 1 mol Cu
3.4 X 1023 atoms Cu
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Learning Check!

• How many atoms of K are present in 78.4 g of K?

53
Learning Check!

• What is the mass (in grams) of 1.20 X 1024
  molecules of glucose (C6H12O6)?

54
Learning Check!

• How many atoms of O are present in 78.1 g of
  oxygen?

78.1 g O2 1 mol O2 6.02 X 1023 molecules O2 2
atoms O 32.0 g O2 1 mol O2
1 molecule O2
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Percent Composition

• What is the percent carbon in C5H8NO4 (the
  glutamic acid used to make MSG monosodium
  glutamate), a compound used to flavor foods and
  tenderize meats?
• a) 8.22 C
• b) 24.3 C
• c) 41.1 C

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Ex ????????????????????????? (CO2) ???? 9.24
g ????????? ?.  ???????? CO2 ?.  ????????????
CO2 ?.  ??????????????????????????????????????
???????? ?.  ?????????????????????? ( C
12.0 O 16.0 )
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• ??????
• ????????????????? CO2
• 12.0 ( 2 x 16.0 )
• 44.0
• ??????????? CO2 9.24 g CO2 ? 1 mol CO2
• 
  
• 
  44.0 g CO2
• 0.210 mol
  CO2

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?.   Molecule CO2 9.24 g CO2? 1 mol CO2 ? 6.02
x 1023 molecule CO2
44.0 g CO2 ? 1
mol CO2
1.26 x 1023 molecule CO2
?.   Mole C 9.24 g CO2? 1 mol CO2 ? 1 mol
C 44.0 g CO2 ? 1
mol CO2
0.210 mole C
Mole O 9.24 g CO2? 1 mol CO2 ? 2
mol O 44.0 g
CO2 ? 1 mol CO2
0.420 mole O
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?.   Atom C 9.24 g CO2? 1 mol CO2 ? 1 mol C
? 6.02 ? 1023 atom C
44.0 g CO2 ? 1 mol CO2
? 1 mol C
1.26 ? 1023 atom C
Atom O 9.24 g CO2? 1 mol CO2 ? 2 mol
O ? 6.02 ? 1023 atom O
44.0 g CO2 ? 1 mol CO2 ? 1 mol O
2.53 ? 1023 atom O
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• Ex. ???????????? ???????????? ?????????? ??? STP
  ??????????????????????? 10.0 g
• ????????? (O3)
• ?????????? (Cl2)
• ????????????? (NH3)

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• Ex. ????
• ????????? (O3)
• 0.208 mol , 1.25 ? 1023 molecule, 4.67 dm3 ???
  STP
• ?????????? (Cl2)
• 0.141 mol , 8.48 ? 1022 molecule, 3.15 dm3 ???
  STP
• ????????????? (NH3)
• 0.587 mol , 3.53 ? 1023 molecule, 13.2 dm3 ???
  STP

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Concept of mole
1. What is the mass of 1.00 mol of each of the
following elements? a.     Sodium.
b.     Sulfur. c.     
Chlorine
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Concept of mole
2. How many moles of sodium atoms in 1.56 x
1021 atoms of sodium?
64
Concept of mole
3. What is the total number of atoms in 0.260
mol of glucose, C6H12O6?
65
Concept of mole
4. Determine the mass in grams of each of the
following a.     1.35 mol Fe b.     24.5 mol
O c.       0.876 mol Ca d.     1.25 mol
Ca3(PO4)2 e.      0.625 mol Fe(NO3)3 f.      
0.600 mol C4H10 g.     1.45 mol (NH4)2CO3
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Concept of mole
5. Calculate the number of moles of each
compound a.   21.5 g CaCO3 b.   1.56 g
NH3 c.   16.8 g Sr(NO3)2 d.   6.98 ?g Na2CrO4
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