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

3
Avogadros Number
6.02x1023
4
How BIG is a mole?

• There are 6.6 billion people on Earth
• How many Earths would it take to equal the
  population of 1 mole?

9.12 x 1013
5

• If you had a mole of cats . . .
• They would create a sphere
• larger than Earth!

6

• If you had a mole of and you spent 800
  billion dollars a day how many years would it
  take to spend a MOLEion dollars?

2.06 x 109 years
7
(No Transcript)
8

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

9
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.

10

• Just one granule of sugar contains 1 x 1017
  molecules
• Each time you take a breath of air, you inhale
  about 2 x 1022 molecules of nitrogen and 5 x 1021
  molecules of oxygen.

11

• In chemistry we dont work with individual atoms
  or molecules because they are too small to be
  weighed or measured
• We have to work with LOTS of atoms in order to
  measure them
• THATs WHERE THE
• MOLE COMES IN!

12
(No Transcript)
13
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

14
PracticeRemember . . .1 mole 6.02x1023 atoms
or molecules ______ g from the periodic table
15
Stoichiometry of Chemical Formulas
16
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

17
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!

18
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?

19
PracticeRemember . . .1 mole 6.02x1023 atoms
or molecules ______ gfm from the pt
20
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

21

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

101.3kPa or 1 atm
22
Remember . . .

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

23
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!

24
Remember . . . 1 mole 6.02x1023 atoms or
molecules gfm 22.4L (g)
25
Stoichiometry of Chemical Equations

• The study of quantitative relationships that can
  be derived from chemical equations.

26
Stoichiometry cookies

• If you look at chemical equations as recipes it
  may be easier to understand that
• changing the amount of a reactant will change the
  amount of the product IN THE SAME RATIO!

27
Examining Molar Relationships in Balanced
Equations

• 6CO2 12 H2O 2804kJ ? 6O2 C6H12O6 6H20
• Balanced equations
• Law of conservation of mass / matter
• ATOMS are not created or destroyed during a
  chemical reaction, they are only rearranged to
  form new substances.
• atoms on reactant side atoms on product
  side
• Law of conservation of E
• E on the reactant side E on the product side

28
Mole - Mole Relationships

• Practice

29
Types of Chemical Reactions
30
SYNTHESIS Reaction

• 2 or more reactants combine to build a single
  product
• General Formula
• A B ? AB
• 3H2 N2 ? 2NH3

31
Particle Diagram
32
DECOMPOSITION reaction

• A compound is broken down into 2 or more simpler
  substances
• General Formula
• AB ? A B
• 2H2O ? 2H2 O2

33
Particle Diagram
34
SINGLE REPLACEMENT reaction

• One of the reactants is a single element. It
  becomes part of a compound as a product.
• General Formula
• A BX ? B AX
• Mg CaBr2 ? Ca MgBr2

35
Particle Diagram
36
DOUBLE REPLACEMENT reaction

• TWO elements switch places during the process of
  the reaction.
• General Formula
• AB CD ? AD CB
• LiCl KBr ? LiBr KCl

37
Particle Diagram
38
Combustion

• Oxygen is always a reactant
• CO2 and H2O are always products
• _______ O2 ? CO2 H2O

39
Practice

• 2Al 3CuSO4 ? Al2(SO4)3 3Cu
• 2H2 O2 ? 2H2O
• C12H22O11 ? 11H2O 12C
• KCl AgNO3 ? KNO3 AgCl
• CH4 2O2 ? CO2 2H2O

40
The End