Starter S-93

1
Starter S-93

1. What is the molar mass of H2S?
2. How many moles of H2S would be found in 100 g?
3. How many formula units (particles) of H2S would
   be in 100g?

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Chemical Quantities

• Chapter 10

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10.1 The Mole A Measurement of Matter

• Chapter 10

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10.1 The Mole

• Quantitative yield a number value
• Most common methods
• count
• mass
• volume

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10.1 The Mole

• Words often mean a quantity
• pair 2
• dozen 12
• mole?

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10.1 The Mole
10.1 The Mole

• Mole means a specific number of particles
• This is called Avogadros Number
• The unit is used for
• atoms
• molecules (covalent compounds)
• formula units (ionic compounds)

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10.1 The Mole
10.1 The Mole

• To convert numbers of particles to moles we need
  an equality
• This could also be
• Or
• Depending on what type of particle you are trying
  to convert

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10.1 The Mole
10.1 The Mole

• The rest is just the conversion we have always
  done
• remember the unit you have goes on the bottom
  of the fraction
• -the unit you are converting to goes on the
  top
• So to convert 2500 atom of C to moles

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10.1 The Mole
10.1 The Mole

• Converting from moles to partciles follows the
  same process
• How many molecules of Carbon Dioxide are in 1.55
  mol?

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10.1 The Mole
10.1 The Mole

• Convert the following quantities to moles
• 1. 9,487,212 formula units of AgNO3
• 2. 5.78x1023 atoms of Nitrogen
• 3. 4.1x1024 molecules of Carbon Monoxide

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10.1 The Mole
10.1 The Mole

• Convert the following to the correct type of
  particle
• 1. 95 moles of CCl4
• 2. 7.211x10-3 moles of CuCO3
• 3. 0.08 moles of Helium

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10.1 The Mole
10.1 The Mole

• By definition, the atomic mass of an element in
  grams is the mass of one mole of the element.
• This is called the molar mass

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10.1 The Mole
10.1 The Mole

• For a compound we must calculate the molar mass
• Write down what type of atoms, and how many of
  each are present
• C 1
• H 4
• 2. Multiply by the molar mass of each element

CH4
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10.1 The Mole
10.1 The Mole

• For a compound we must calculate the molar mass
• Write down what type of atoms, and how many of
  each are present
• C 1 x 12.0107g
• H 4 x 1.00794g
• 2. Multiply by the molar mass of each element

CH4
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10.1 The Mole
10.1 The Mole

• For a compound we must calculate the molar mass
• Write down what type of atoms, and how many of
  each are present
• C 1 x 12.0107g 12.0107g
• H 4 x 1.00794g 4.03176g
• Multiply by the molar mass of each element
• Add to get a total

CH4
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10.1 The Mole
10.1 The Mole

• For a compound we must calculate the molar mass
• Write down what type of atoms, and how many of
  each are present
• C 1 x 12.0107g 12.0107g unit
• H 4 x 1.00794g 4.03176g
• Multiply by the molar mass of each element
• Add to get a total 16.0425g CH4

CH4
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Starter S-94

1. What is the molar mass of CO?
2. How many moles of CO would be found in 0.56 g?
3. How many molecules of CO would be found in 3.51
   moles?

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10.2 Mole-Mass and Mole-Volume

• Chapter 10

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10.1 The Mole
10.2 Mole-Mass and Mole-Volume

We dont convert from particles to moles nearly
as often as we do from moles to grams. The reason
is that we usually measure the amount of a
substance on the balance We need to know numbers
of particles so that we can compare
ratios of atom or compounds
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10.1 The Mole
10.2 Mole-Mass and Mole-Volume
This is just another conversion problem The
equality is Again, the quantity you have goes
on the bottom, the quantity you want goes on
top So if you have 9.5g of Carbon

Value Molar Mass 1 mole
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10.1 The Mole
10.2 Mole-Mass and Mole-Volume
If you have 2.2 moles of Silver Nitrate convert
to mass First we need to know the formula of
Silver Nitrate Then the molar mass And
finally we can convert

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10.1 The Mole
10.2 Mole-Mass and Mole-Volume
Try the following example How many moles is 8.2g
of Copper (II) Chloride Formula Molar
mass Moles

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10.1 The Mole
10.2 Mole-Mass and Mole-Volume
And another one How many grams is 2.4 mol of
Iron (III) Sulfate Formula Molar mass Moles

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10.1 The Mole
10.2 Mole-Mass and Mole-Volume
In 1811, Amedeo Avogadro proposed Avagadors
Hypothesis equal volumes of gases at the same
temperature and pressure contain equal numbers of
particles

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10.1 The Mole
10.2 Mole-Mass and Mole-Volume
Standard Temperature and Pressure (STP) T 0oC
or 273K P 101.3 kPa, or 1 atm At STP the
volume of one mole is 22.4L So the equality for
conversion is

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10.1 The Mole
10.2 Mole-Mass and Mole-Volume
To do these problems, the identity of the gas
doesnt really matter. If we have 15 L of
Chlorine gas The number of moles would be

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10.1 The Mole
10.2 Mole-Mass and Mole-Volume
If instead we calculate for a more complicated
gas such as propane And we also have 15 L of
propane gas The number of moles would be

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Starter S-95

1. What is the molar mass of Pb(SO4)2?
2. How many moles of Pb(SO4)2 would be found in 250
   g?
3. How many moles of H2 gas are found in 250 L?

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10.3 Percent Composition and Chemical Formulas

• Chapter 10

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10.1 The Mole
10.3 Percent Composition
The relative amounts of the elements in a
compound is called the percent composition The
percent by mass of an element is the number
of grams of the element divided by
the mass in grams of the compound
multiplied by 100

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10.1 The Mole
10.3 Percent Composition

• Calculating the mass percent from a formula
• Formula
• Calculate the total
• mass of each element
• Calculate the total
• mass of
• the compound
• Calculate the
• percent by
• mass for
• each element

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10.1 The Mole
10.3 Percent Composition

• Calculate the mass percent
• Formula
• Mass of each element
• Total mass
• Mass Percent

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Starter S-98

• What is the percent by mass of the all the
  elements in Cu(NO3)2.

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10.1 The Mole
10.3 Percent Composition
Empirical Formula smallest whole number ratio
of the elements in a compound The
empirical formula can be calculated
from the percent composition

Compound Empirical Formula
H2O H2O
CH3COOH CH2O
CH2O CH2O
C6H12O6 CH2O
S8 S
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10.1 The Mole
10.3 Percent Composition

• To calculate the empirical formula
• List the elements and their
• percent compositions
• Convert the percent
• compositions to moles
• Calculate the mole ratio (divide
• by the smallest number of moles)
• Smallest Whole Number ratio
• Write the Formula

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10.1 The Mole
10.3 Percent Composition

• To calculate the empirical formula
• Elements
• Convert to Moles
• Mole ratio
• Whole Number ratio
• Write the Formula

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Starter S-99

• What is the empirical formula if
• Lead is 59.7
• Hydrogen is 2.9
• Arsenic is 21.6
• Oxygen is 18.4

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10.1 The Mole
10.3 Percent Composition
The molecular formula can be calculated from the
empirical formula and the molar mass
Comparison of Empirical and Molecular Formulas Comparison of Empirical and Molecular Formulas Comparison of Empirical and Molecular Formulas
Formula Classification Molar Mass
CH Empirical 13
C2H2 Molecular 26 (2x13)
C6H6 Molecular 78 (6x13)
CH2O Empirical 30
C2H4O2 Molecular 60 (2x30)
C6H12O6 Molecular 180 (6x30)
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10.1 The Mole
10.3 Percent Composition

• Steps in calculations (if mass60.0g)
• Determine the empirical formula
• Calculate the mass
• of the empirical formula
• Divide the actual molar mass by
• this number
• 4. Multiply the empirical formula

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Starter S-102

• What is the empirical formula if
• Silver 63.5
• Nitrogen 8.2
• Oxygen 28.2
• If the formula mass is 170g, what is the formula
  of this compound?

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Starter S-103

• What is the empirical formula if
• Carbon 49.5
• Hydrogen 5.2
• Nitrogen 28.9
• Oxygen 16.5
• What if the molecular formula, if the molar mass
  is 194g?