The Mole

1
The Mole
1 dozen
12
1 gross
144
1 ream
500
1 mole
6.02 x 1023
2
Avogadros Number
6.02 x 1023 is called Avogadros Number in
honor of the Italian chemist Amadeo Avogadro
(1776-1855).
I didnt discover it. Its just named after me!
Amadeo Avogadro
3
Page 291, 3
4
Page 291, 4
5
Calculations with MolesUsing Avogadros Number
How many atoms of lithium are in 3.50 moles of
lithium?
3.50 mol Li
6.02 x 1023 atoms Li
atoms Li
2.11 x 1024
mol Li
6
Page 292, 5
7
Page 292, 6
8
Review Molar Mass
A substances molar mass (molecular weight) is
the mass in grams of one mole of the compound.
CO2 44.0 grams per mole
H2O 18.0 grams per mole
Ca(OH)2 74.0 g/mol
9
Page 296, s 7-8
PCl3
10
Calculations with MolesConverting moles to grams
How many grams of lithium are in 3.50 moles of
lithium?
3.50 mol Li
7.0 g Li
g Li
25
mol Li
11
Calculations with MolesConverting grams to moles
How many moles of lithium are in 18.2 grams of
lithium?
18.2 g Li
mol Li
mol Li
2.6
7.0 g Li
12
Calculations with MolesUsing Avogadros Number
How many atoms of lithium are in 18.2 g of
lithium?
18.2 g Li
mol Li
6.02 x 1023 atoms Li
7.0 g Li
mol Li
atoms Li
1.6 x 1024
(18.2)(6.02 x 1023)/7.0
13
Standard Molar Volume
Equal volumes of all gases at the same
temperature and pressure contain the same number
of molecules. - Amedeo Avogadro
14
Standard Molar Volume
15
Standard Temperature and PressureSTP

• P 1 atmosphere, 101.3 kPa
• T 0C, 273 Kelvins
• The molar volume of an ideal gas is 22.4
  liters at STP

16
Calculating Percentage Composition
Calculate the percentage composition of magnesium
carbonate, MgCO3.
24.0 g 12.0 g 3(16.0 g) 84.0 g
100.00
17
Formulas
Empirical formula the lowest whole number ratio
of atoms in a compound.
Molecular formula the true number of atoms of
each element in the formula of a compound.

• molecular formula (empirical formula)n n
  integer
• molecular formula C6H6 (CH)6
• empirical formula CH

18
Formulas (continued)
Formulas for ionic compounds are ALWAYS empirical
(lowest whole number ratio).
Examples
NaCl
MgCl2
Al2(SO4)3
K2CO3
19
Formulas (continued)
Formulas for molecular compounds MIGHT be
empirical (lowest whole number ratio).
Molecular
C6H12O6
C12H22O11
H2O
Empirical
H2O
CH2O
C12H22O11
20
Empirical Formula Determination

• Base calculation on 100 grams of compound.
• Determine moles of each element in 100 grams of
  compound.
• Divide each value of moles by the smallest of the
  values.
• Multiply each number by an integer to obtain all
  whole numbers.

21
Empirical Formula Determination
Adipic acid contains 49.32 C, 43.84 O, and
6.85 H by mass. What is the empirical formula of
adipic acid?
22
Empirical Formula Determination(part 2)
Divide each value of moles by the smallest of the
values.
Carbon
Hydrogen
Oxygen
23
Empirical Formula Determination(part 3)
Multiply each number by an integer to obtain all
whole numbers.
Carbon 1.50
Hydrogen 2.50
Oxygen 1.00
x 2
x 2
x 2
3
5
2
C3H5O2
Empirical formula
24
Finding the Molecular Formula
The empirical formula for adipic acid is C3H5O2.
The molecular mass of adipic acid is 146 g/mol.
What is the molecular formula of adipic acid?
1. Find the formula mass of C3H5O2
3(12.0 g) 5(1.0) 2(16.0) 73.0 g
25
Finding the Molecular Formula
The empirical formula for adipic acid is C3H5O2.
The molecular mass of adipic acid is 146 g/mol.
What is the molecular formula of adipic acid?
3. Multiply the empirical formula by this number
to get the molecular formula.
3(12.0 g) 5(1.0) 2(16.0) 73.0 g
(C3H5O2) x 2
C6H10O4
26
(No Transcript)