Download Part of a Molecular Compound

Chemical Quantities
Chapter 7
Representative Particles
• The smallest divisible unit of a
substance
• Elements – Atoms
• Molecular Compounds – Molecules
• Ionic Compounds – Formula Units
• Part of a Molecular Compound –
– Atom
• Part of an Ionic Compound - ion
The Mole
• Quantity equal to 6.022 x 1023
representative particles.
• 602200000000000000000000
particles
• A.k.a
Avogadro's Number
How big is a mole?
• A mole of hockey pucks is equal to
the mass of the moon.
How big is a mole?
• A mole of rice would occupy a cube
with sides of about 120 miles!
How big is a mole?
• A mole of rice grains is more grains
then the number of grains of all grain
grown since the beginning of time!
How big is a mole?
• If you had a mole of pennies, you could
buy kite string at a million dollars an inch.
With this string you could wrap it around
the earth a million times and to the moon
and back 25 times. You could sell the left
over string back at a penny an inch ( a
major loss) and take the remaining money
and give everyone in the world about
$10,000.
O.K. seriously…How big is
a mole?
• How much is a mole of water
molecules?
• Let me show you!
Now for some math…
• How many moles is 3.78 x 1022
atoms of magnesium?
Example 2
• How many moles is 3.78 x 1022
molecules of sulfur dioxide?
Example 3
• How many moles is 1.80 x 1021
formula units of sodium sulfate?
Example 4
• How many atoms in 0.750 moles of
zinc?
Example 5
• How many molecules in 0.750 moles
of carbon dioxide?
Example 6
• How many formula units in 1.22
moles of iron (III) chloride?
Example 7
• How many atoms of hydrogen are in
5.15 mol of methane (CH4)?
Example 8
• How many ions of potassium are in
0.80 mol of potassium carbonate?
Example 9
• How many ions of nickel are in 0.80
mol of nickel (II) oxalate?
Molar Mass
Chapter 7
Molar Mass
• The mass in grams of one mole of
substance.
• Older terms you might hear
– Molecular weight
– Formula weight
Calculating Molar Mass
• Use the atomic masses on the periodic
table.
• On many of them you can round to the
nearest gram, except for elements that
atomic masses end in 0.5
• Use as many significant figures needed to
maintain the number of significant figures
given in the problem.
Example 1
• What is the molar mass of
selenium?
• mm = 78.96 g/mol
Example 2
• What is the molar mass of nitrogen
gas (N2)?
• mm = 2 x 14.0 = 28.0 g/mol
Example 3
• What is the molar mass of water
(H2O)?
– H 2 x 1.0 = 2.0
– O 1 x 16.0 = 16.0
– mm = 18.0 g/mol
Example 4
• What is the molar mass of Tin (II)
Chloride?
– SnCl2
– Sn 1 x 119 = 119
– Cl 2 x 35.5 = 71
– mm = 190 g/mol
Mole Map
Periodic Table
Mole
Molar Mass
Avogadro's Number
6.022 x 1023
Mass (g)
Representative
Particles
Molecules
Formula Units
Atoms
Ions
Atoms
Example 5
• How many atoms are in 5.6 mol of
iron?
Example 6
• How many grams are in 5.6 mol of
iron?
Example 7
• How many atoms are in 5.6 g of
iron?
Example 8
• How many grams does 3.4 x 1024
atoms of Sodium weigh?
Example 9
• How many moles is 125 g of
calcium?
Empirical and Molecular
Formulas
Chapter 7
Empirical Formula
• A formula with the lowest whole
number ratio of elements.
• Examples
H2O2 (molecular formula) = HO (empirical formula)
H2O = H2O
C12H22O10 = C6H11O5
• Several different formulas can yield the
same empirical formula.
Steps for solving empirical
formula problems
1. Convert grams to moles. (If in
percent, treat as grams.)
2. Divide by lowest mole.
3. If not in whole number ratio,
multiply by a common whole
number to get a whole number
ratio.
Example 1
• Find the empirical formula of a
compound that is 25.9g N and 74.1g
O.
Example 2
• 1.58 g of copper was reacted with
sulfur to produce a compound with a
mass of 1.98 g. What is the
empirical formula for the compound?
Example 3
• Find the empirical and molecular
formula of a compound that is 67.6%
Hg, 10.8% S and the balance O.
The molar mass of the compound is
891 g/mol.
Molar Volume
Chapter 7
Molar Volume
• The volume of one mole of a gas.
• At STP, the volume of one mole of
gas is 22.4 L
• STP = standard temperature and
pressure
– Standard Temperature = 0oC
– Standard Pressure = 1 atm
• Atm = atmosphere
Mole Map
Volume (L)
At STP 1 mole =
22.4L
Periodic Table
Mole
Molar Mass
Avogadro's Number
6.022 x 1023
Mass (g)
Representative
Particles
Molecules
Formula Units
Atoms
Ions
Atoms
Example 1
• What is the volume of 0.60 moles of
SO2 at STP?
Example 2
• What is the volume in mL of 90 g of
SO2 at STP?
Percent Composition
Chapter 7
Percent Composition
• Percent by mass of elements in a
compound.
Example 1
• Find the percent composition of
potassium chromate.
Example 2
• What is the percent sodium in
sodium fluoride?
Example 3
• How many grams of a 40 g sample
of sodium fluoride is sodium?