jan. 12. to do today turn in hw sheet go over answers lecture note slides: hand back graded quizzes
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Jan. 12
To Do Today
• Turn in HW Sheet
• Go over answers
• Lecture Note Slides:
• Hand back graded quizzes
Relating mass (grams) to Number of atoms
• Using “The Mole”
History of the term “mole”
• Mole is the English version of the German word "Mol" which is short for Molekulargewicht, the "molecular weight.“
• There are claims that it originated as a latin term meaning Mass.
• Started being used around 1900• Used in textbooks by 1950s
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• Q: What does Avogadro put in his hot chocolate?
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•A: Marsh-mole-ows!
Q: What did the generous mole say when his friends crashed his party?
A: The mole the merrier!
Definition of “mole”
• Amount of a substance that contains as many particles as there are atoms in exactly 12 g of carbon-12.
• This Amount is 6.02 x 1023
• It is a “counting unit” just as 1 dozen = 12 of anything.
• 1 mole = 6.02 x 1023 particles
– Chemistry involves vast numbers of atoms.
– we need a convenient unit used for counting atoms.
– (it takes about 500,000 trillion million carbon atoms to equal just one gram.)
– The unit used in Chemistry is the “MOLE”
The Mole Info
• The mole, a fundamental SI unit for "amount of substance," is defined precisely as the number of carbon atoms in 12.01 g of carbon.
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The Mole Info• It is here that the value of
Avogadro's number becomes clear: as noted, carbon has an average atomic mass of 12.01 amu, and multiplication of the average atomic mass by Avogadro's number yields a figure in grams equal to the value of the average atomic mass in atomic mass units. THEREFORE……
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• The mass of 1 mole of any element is equal to its atomic mass expressed in grams
Atomic masses can be found in the periodic table.
– Example:
• C = 12.01 amu
• 1 mol C = 12.011 g C
– Example:
• He = 4 amu
• 1 mol He = 4 g He
– Example:
• N = 14 amu
• 1 mol N = 14 g N
Molar Mass
• The mass of one mole of a substance is called the molar mass of that substance.
• Molar mass is written in g/mol
Molar Mass
• The molar mass of an element is equal to the atomic mass of the element.
• Molar Mass of lithium is
• 6.94 g/mol
• Molar Mass of mercury is
• 200.59 g/mol
Relating grams to # of atoms
• The molar mass of an element contains one mole of atoms.
• In other words, 1 mole of an element contains 6.02 x 1023 atoms of the element
• 1 mole He = 4 grams He = 6.02 x 1023
atoms of He
What is the mass (in grams) of 3.50 mol of copper, Cu?
• Given: 3.50 mol of Cu• Convert between grams and moles using
molar mass• moles of Cu x (g Cu) = grams Cu
moles Cu
3.50 mol Cu x __________ = 222 g Cu63.55 g Cu1 mol Cu
3.50 mol Cu x __________ = 222 g Cu63.55 g Cu1 mol Cu
3 sig digits
What is the mass in grams of 2.25 mol of Fe?
2.25 mol Fe x __________ = 126 g Cu55.85 g Fe
1 mol Fe
3 sig digits
Conversions between grams, moles and # of atoms or
molecules
grams moles# of atoms or molecules
molar m
ass
6.02 x 1023
P 219
• Monatomic ions
• Binary ionic compounds
• Stock system for elements in d block
• Polyatomic ions
• Molecular compounds
P 237
• Formula mass
• Molar mass
• Percentage composition
• Calculation of empirical formulas
• Calculation of molecular formulas
Review equations and reactions
• Balancing equations
• P 268 – 9 molar ratios
• Types of reactions
• Predicting products
Stoichiometry
• Ch 9
Gases
• Gas law
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