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AP Chemistry Chapter 3
Chemical Chemical QuantitiesQuantities(The Mole) (The Mole)
Amedeo AvogadroHypothesis: Equal volumes of different gases at the same temperature and pressure contain equal numbers of particles.
Amadeo Avogadro
H2
hydrogenCH4
methane
The Mole
1 dozen =1 gross =
1 ream =
1 mole =
12
144
500
6.02 x 1023
There are exactly 12 grams of carbon-12 in one mole of carbon-12.
Avogadro’s Number6.02 x 1023 is called “Avogadro’s Number” in honor of the Italian chemist Amedeo Avogadro (1776-1855).
Amadeo Avogadro
I didn’t discover it. Its just named after
me!
The Mole (Quantities)
1 mole =
1 mole =
1 mole =
atoms molecules formula units
Molar mass (periodic table)
22.4 L for a gas @STP
6.02 x 1023
(elements) (nonmetals) (cation-anion)
Mass:
Volume:
Representative Particles:
1. Convert 3.00 moles of ammonia, NH3, to grams of ammonia.
1. Convert 3.00 moles of ammonia, NH3, to grams of ammonia.
1 mole NH3 = ?? g NH3
Conversion factor:
3.00 mol NH3x = g NH3
You have to find molar mass.(Use Periodic
Table)
mol NH3
g NH3
17.04 g NH17.04 g NH33
NHNH33
14.01 g14.01 g 1.01 g1.01 gx 3x 3
14.01 g14.01 g + 3.03 g =+ 3.03 g =x 1x 1
Molar mass of ammonia.
7
N14.01
1
H1.01
1 mole NH3 = 17.04 g NH3
1. Convert 3.00 moles of ammonia, NH3, to grams of ammonia.
1 mole NH3 = 17.04 g NH3
Conversion factor:
3.00 mol NH3x = g NH3
mol NH3
g NH3
NH3
14.01 1.01x 1 x 314.01 g+ 3.03 g = 17.04 g/mol
1 17.04
On calculator: 3.00 x 17.04 = 51.12
Round to 3 sig. figs.
51.1 g NH3
Ch. 7 (Calculating Chemical Quantities)
3.
2.
3NHmol00.3 17.04 g NH3
1 mol NH314.01 1.01x 1 x 314.01 g + 3.03 g = 17.04 g/mol
1. = 51.1 g NH3
2. How many molecules of carbon dioxide are in 2.00 moles of CO2?
2. How many molecules of carbon dioxide are in 2.00 moles of CO2?
1 mole CO2 = 6.02 x 1023 molecules CO2
Conversion factor:
2.00 mol CO2x = molec. CO2
1 mole = 6.02 x 1023 representative
particles
CO2 is made of all nonmetals sorep. particles are “molecules”
mol CO2
molec. CO2
2. How many molecules of carbon dioxide are in 2.00 moles of CO2?
1 mole CO2 = 6.02 x 1023 molecules CO2
Conversion factor:
2.00 mol CO2x = molec. CO2mol
CO2
molec. CO2
1 6.02 x 1023
On calculator: 2.00 x (6.02 x 1023) = 1.204 x 1024
Round to 3 sig. figs.
1.20 x 1024 molec. CO2
Ch. 7 (Calculating Chemical Quantities)
3.
2
2 23
2 COmol 1
CO molec.10x 6.02COmol002. 1.20 x 1024
molec. CO2
2.
3NHmol00.3 17.04 g NH3
1 mol NH314.01 1.01x 1 x 314.01 g + 3.03 g = 17.04 g/mol
1. = 51.1 g NH3
3. How many moles of oxygen are in 44.8 L of oxygen, O2?
1 mole O2 = 22.4 L O2
Conversion factor:
44.8 L O2 x = moles O2
1 mole = 22.4 L (for any gas @ STP)
L O2
mol O2
1 22.4
On calculator: 44.8 ÷ 22.4 = 2
Show to 3 sig. figs.
2.00 moles O2
Ch. 7 (Calculating Chemical Quantities)
2
22 OL 22.4
O mole 1O L 44.8 2.00 mol O23.
2
2 23
2 COmol 1
CO molec.10x 6.02COmol002. 1.20 x 1024
molec. CO2
2.
3NHmol00.3 17.04 g NH3
1 mol NH314.01 1.01x 1 x 314.01 g + 3.03 g = 17.04 g/mol
1. = 51.1 g NH3
4. How many grams of lithium are in 3.50 moles of lithium?
1 mole Li = g Li
Conversion factor:
3.50 mol Li x = g Limol Li
g Li
1 6.94
On calculator: 3.50 x 6.94 = 24.29
Round to 3 sig. figs.
24.3 g Li
The Mole (Quantities)
1 mole =
1 mole =
1 mole =
atoms molecules formula units
Molar mass (periodic table)
22.4 L for a gas @STP
6.02 x 1023
(elements) (nonmetals) (cation-anion)
Mass:
Volume:
Representative Particles:
5. How many moles of lithium are in 18.2 grams of lithium?
1 mole Li = g Li
Conversion factor:
18.2 g Li x = mol Lig Li
mol Li
1 6.94
On calculator: 18.2 ÷ 6.94 = 2.6225
Round to 3 sig. figs.
2.62 mol Li
Representative Particles:Using Avogadro’s Number
6. How many atoms of lithium are in 3.50 moles of lithium?
3.50 mol Li
= atoms Li1 mol Li
6.02 x 1023 atoms Li 2.11 x 1024
Use 6.02 x 1023 when looking for atoms, molecules, or formula units
x
Representative Particles:Two-part problem
7. How many atoms of lithium are in 18.2 g of lithium?
18.2 g Li
= atoms Li
1 mol Li 6.02 x 1023 atoms Li
1.58 x 1024
6.94 g Li 1 mol Li
(18.2)/6.94 x (6.02 x 1023)
x x
%Na
X 100 =26.00 g
7.86 g= 30.23 % Na
%Cl X 100 =26.00 g
18.14 g= 69.77 % Cl
8. A sample of sodium chloride, (NaCl) commonly called table salt contains 7.86 g of sodium and 18.14 g of chlorine. Find the % composition.Find total mass of NaCl 7.86 g
+ 18.14 gTotal mass = 26.00 g
Take the mass of the element divided by total mass.
%C X 100 =44.11 g
36.03 g=
44.11 g C3H8
CC33HH88
12.01 g 1.01 gx 8
36.03 g + 8.08 g =
x 3
81.68 % C
%H X 100 =44.11 g
8.08 g= 18.32 % H
9. Find the % composition of propane, (C3H8).
6
C12.01
1
H1.01
10. A 12.8 g sample of a gas contains 6.4 grams of sulfur and 6.4 grams of oxygen. What is the empirical formula for this gas?
Formulas
molecular formula = (empirical formula)n where n = integer
molecular formula = C6H6 = (CH)6
empirical 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.
Formulas (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
All can be divided by 6
Empirical Formula Determination
1. Convert grams values to moles for each element.
2. Divide by lowest moles.
3. If necessary: Multiply each number by an integer to obtain all whole numbers.
6.4 g S =32.07 g S
1 mol Sx 0.1995 mol S = 0.20 mol S
6.4 g O = 0.4 = 0.40 mol O16.00 g O
1 mol Ox
10. A 12.8 g sample of a gas contains 6.4 grams of sulfur and 6.4 grams of oxygen. What is the empirical formula for this gas?
16
S32.07
8
O16.00
0.20 mol
0.20 mol
2. Divide by lowest moles.
1. Convert to moles.
2
1
S OSO2Empirical Formula
3.2 g H =1.01 g H
1 mol Hx 3.16 mol H
19.4 g C = 1.6212.01 g C
1 mol Cx
11. An unknown clear colorless liquid with no odor is analyzed and found to contain the following. Determine the empirical formula.
1
H1.01
8
O16.00
1.6 mol
1.6 mol
2. Divide by lowest moles.
1. Convert to moles.
1
2
H C OEmpirical Formula
3.2 % Hydrogen19.4% Carbon77.4% Oxygen
Assume 100 g sample
= 3.2 g H= 19.4 g C= 77.4 g O
77.4 g O = 4.8416.00 g O
1 mol Ox
1.6 mol 3
6
C12.01
H2CO3
= 3.2 mol H
= 1.6 mol C
= 4.8 mol O
%Na
X 100 =58.44 g
22.99 g=
58.44 g NaCl
NaClNaCl22.99 g 35.45 g
x 1
22.99 g + 35.45 g =
x 1
39.34 % Na
%O X 100 =58.44 g
35.45 g= 60.66 % Cl
8. A sample of sodium chloride, (NaCl) commonly called table salt contains 7.86 g of sodium and 18.14 g of chlorine. Find the % composition. 11
Na22.99
17
Cl35.45
The Mole (Quantities)
1 mole =
1 mole =
1 mole =
atoms molecules formula units
Molar mass (periodic table)
22.4 L for a gas @STP
6.02 x 1023
(elements) (nonmetals) (cation-anion)
Mass:
Volume:
Representative Particles: