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Avogadro’s NumberAvogadro’s Number6.02 x 1023 is called “Avogadro’s Number” in honor of the Italian chemist Amadeo Avogadro (1776-1855).
Amadeo Avogadro
I didn’t discover it. Its just named after
me!
Calculations with Moles:Calculations with Moles:Using Avogadro’s NumberUsing Avogadro’s Number
How many atoms of lithium are in 3.50 moles of lithium?
3.50 mol Li = atoms Li
mol Li
6.02 x 1023 atoms Li 2.11 x 1024
ReviewReview: Molar : Molar MassMass
A substance’s A substance’s molar mass molar mass (molecular weight) is the mass in (molecular weight) is the mass in grams of one mole of the compound. grams of one mole of the compound.
COCO22 = 44.0 grams per mole = 44.0 grams per mole
HH22O = 18.0 grams per moleO = 18.0 grams per mole
Ca(OH)Ca(OH)22 = 74.0 g/mol = 74.0 g/mol
Calculations with Moles:Calculations with Moles:Converting moles to gramsConverting moles to grams
How many grams of lithium are in 3.50 moles of lithium?
3.50 mol Li= g Li
mol Li
7.0 g Li25
Calculations with Moles:Calculations with Moles:Converting grams to molesConverting grams to moles
How many moles of lithium are in 18.2 grams of lithium?
18.2 g Li= mol Li
7.0 g Li
mol Li2.6
Calculations with Moles:Calculations with Moles:Using Avogadro’s NumberUsing Avogadro’s Number
How many atoms of lithium are in 18.2 g of lithium?
18.2 g Li
= atoms Li
mol Li 6.02 x 1023 atoms Li
1.6 x 1024
7.0 g Li mol Li
(18.2)(6.02 x 1023)/7.0
Standard Molar Standard Molar VolumeVolume
Equal volumes of all gases at the same temperature and pressure contain the same number of molecules.
- Amedeo Avogadro
Standard Temperature and Standard Temperature and PressurePressure
“STP”“STP”
P = 1 atmosphere, 101.3 kPa T = C, 273 Kelvins The molar volume of an ideal gas is 22.4 liters at STP
Calculating Percentage Calculating Percentage CompositionComposition
Calculate the percentage composition of Calculate the percentage composition of magnesium carbonate, MgCOmagnesium carbonate, MgCO33..
24.0 g + 12.0 g + 3(16.0 g) = 84.0 g24.0 g + 12.0 g + 3(16.0 g) = 84.0 g
24.31100 28.83%
84.32Mg
12.01
100 14.24%84.32
C 48.00
100 56.93%84.32
O
100.00
FormulasFormulas
molecular formula = (empirical molecular formula = (empirical formula)formula)nn [ [nn = integer] = integer]
molecular formula = Cmolecular formula = C66HH66 = (CH) = (CH)6 6
empirical formula = CHempirical formula = CH
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.
FormulasFormulas (continued)(continued)
Formulas for Formulas for ionic compoundsionic compounds are are ALWAYSALWAYS empirical (lowest whole empirical (lowest whole number ratio).number ratio).Examples:Examples:
NaCl MgCl2 Al2(SO4)3 K2CO3
FormulasFormulas (continued)(continued)
Formulas for Formulas for molecular compoundsmolecular compounds MIGHTMIGHT be empirical (lowest whole be empirical (lowest whole number ratio).number ratio).
Molecular:Molecular:
H2O
C6H12O6 C12H22O11
Empirical:
H2O
CH2O C12H22O11
Empirical Formula Empirical Formula DeterminationDetermination
1.1. Base calculation on 100 grams of Base calculation on 100 grams of compound. compound.
2.2. Determine moles of each element in 100 Determine moles of each element in 100 grams of compound. grams of compound.
3.3. Divide each value of moles by the Divide each value of moles by the smallest of the values. smallest of the values.
4.4. Multiply each number by an integer to Multiply each number by an integer to obtain all whole numbers.obtain all whole numbers.
Empirical Formula Empirical Formula DeterminationDetermination
Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid?
49.32 14.107
12.01
g C mol Cmol C
g C
6.85 16.78
1.01
g H mol Hmol H
g H
43.84 12.74
16.00
g O mol Omol O
g O
Empirical Formula Empirical Formula DeterminationDetermination
(part 2)(part 2)
4.1071.50
2.74
mol C
mol O
6.782.47
2.74
mol H
mol O
2.741.00
2.74
mol O
mol O
Divide each value of moles by the smallest Divide each value of moles by the smallest of the values.of the values.
Carbon:Carbon:
Hydrogen:Hydrogen:
Oxygen:Oxygen:
Empirical Formula Empirical Formula DeterminationDetermination
(part 3)(part 3)Multiply each number by an integer to Multiply each number by an integer to obtain all whole numbers.obtain all whole numbers.
Carbon: 1.50Carbon: 1.50 Hydrogen: 2.50Hydrogen: 2.50 Oxygen: 1.00Oxygen: 1.00x 2 x 2 x 2
33 55 22
Empirical formula:C3H5O
2
Finding the Molecular Finding the Molecular FormulaFormula
The empirical formula for adipic acid The empirical formula for adipic acid is Cis C33HH55OO22. The molecular mass of . The molecular mass of adipic acid is 146 g/mol. What is the adipic acid is 146 g/mol. What is the molecular formula of adipic acid?molecular formula of adipic acid?
1. Find the formula mass of 1. Find the formula mass of CC33HH55OO22
3(12.0 g) + 5(1.0) + 2(16.0) = 73.0 g3(12.0 g) + 5(1.0) + 2(16.0) = 73.0 g
Finding the Molecular Finding the Molecular FormulaFormula
The empirical formula for adipic acid The empirical formula for adipic acid is Cis C33HH55OO22. The molecular mass of . The molecular mass of adipic acid is 146 g/mol. What is the adipic acid is 146 g/mol. What is the molecular formula of adipic acid?molecular formula of adipic acid?
3(12.0 g) + 5(1.0) + 2(16.0) = 73.0 g3(12.0 g) + 5(1.0) + 2(16.0) = 73.0 g
1462
73
3. Multiply the empirical formula by 3. Multiply the empirical formula by this number to get the molecular this number to get the molecular formula.formula.
(C(C33HH55OO22) x 2 ) x 2 ==
CC66HH1010OO44