Download - Chapter 19: Molecules and Compounds
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Chapter 19: Molecules Chapter 19: Molecules and Compoundsand Compounds
Section 19.3Section 19.3
Comparing Comparing MoleculesMolecules
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COMPARING DIFFERENT COMPARING DIFFERENT MOLECULESMOLECULES
•How does the How does the mass of different mass of different
molecules molecules compare?compare?
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Do you think that a molecule of water has the same mass as a molecule
of calcium carbonate?
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Recall atomic mass Recall atomic mass units (amu)…units (amu)…
•Atoms are assigned a Atoms are assigned a ____________ __________ __________ on on carboncarbon as the as the standard.standard.•Known as Known as atomic mass unitatomic mass unit
6
CCarbon12.0107
24
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19.3 Comparing 19.3 Comparing MoleculesMolecules
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Chemical formula Chemical formula gives 3 pieces of info:gives 3 pieces of info:
–_____ / _______ of atoms._____ / _______ of atoms.– if ________ ions are if ________ ions are
present.present.– allows calculation of mass allows calculation of mass
of 1 molecule of a of 1 molecule of a compound relative to mass compound relative to mass of other compounds.of other compounds.
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Formula MassFormula Mass
• Formula mass is determined Formula mass is determined by _____ up the atomic mass by _____ up the atomic mass unit (amu) of all the atoms in unit (amu) of all the atoms in the compound.the compound.
• The atomic masses are listed The atomic masses are listed on the ________ table.on the ________ table.
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Example:Example: Figuring Figuring Formula MassFormula Mass
•HH22O means 2H and 1OO means 2H and 1O
• 2 (1.01 amu) =_____ 2 (1.01 amu) =_____ +1 (16.00 amu) = +1 (16.00 amu) = ________
•Formula massFormula mass = ____= ____amu of Hamu of H22OO
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An amu is very small, An amu is very small, so to be usable in so to be usable in measurements, we measurements, we equate the equate the ______________ ____________ of the of the formulaformula massmass in in amuamu to an to an equalequal amountamount in in __________. .
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Avogadro’s NumberAvogadro’s Number
• The formula mass in The formula mass in grams of any element or grams of any element or compound contains compound contains ____ ____ ____________ atoms or atoms or molecules.molecules.• Known as Avogadro’s # or Known as Avogadro’s # or
a a “____”“____” of the substance. of the substance.
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So, how do we So, how do we use this value?use this value?
• If you measure out 100.09 If you measure out 100.09 grams of CaCOgrams of CaCO33, you have , you have 6.02 x 106.02 x 102323 molecules of molecules of CaCOCaCO33..• Likewise, 18.02 g of HLikewise, 18.02 g of H22O O
contains 6.02 x 10contains 6.02 x 102323 molecules molecules of water.of water.
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Example: BaClExample: BaCl2 2 2H2H22OO
• 1 Ba = 1(137.30) = 137.301 Ba = 1(137.30) = 137.30
• 2 Cl = 2(35.45) = 70.902 Cl = 2(35.45) = 70.90
• 4 H = 4(1.01) = 4.044 H = 4(1.01) = 4.04
• 2 O = 2(16.00) = 2 O = 2(16.00) = 32.0032.00 Formula mass = 244.24 Formula mass = 244.24 amuamu