Transcript Chemistry: Matter and Change

Section 10.1 Measuring Matter
• Explain how a mole is
used to indirectly count
the number of particles of
matter.
molecule: two or more
atoms that covalently
bond together to form a
unit
• Relate the mole to a
common everyday
counting unit.
mole
• Convert between moles
and number of
representative particles.
Avogadro’s number
Chemists use the mole to count atoms,
molecules, ions, and formula units.
Counting Particles
• Chemists need a convenient method for
accurately counting the number of atoms,
molecules, or formula units of a substance.
• The _______ is the SI base unit used to
measure the amount of a substance.
• 1 mole is the amount of atoms in 12 g of pure
carbon-12, or 6.02  1023 atoms.
• The number is called ___________________
Converting Between Moles and Particles
• Conversion factors must be used.
• Moles to particles
Number of molecules in 3.50 mol of sucrose
Converting Between Moles and Particles (cont.)
• Particles to moles
• Use the inverse of Avogadro’s number as the
conversion factor.
Section 10.2 Mass and the Mole
• Relate the mass of an atom conversion factor: a
to the mass of a mole of
ratio of equivalent
atoms.
values used to express
the same quantity in
• Convert between number
different units
of moles and the mass of
an element.
• Convert between number
of moles and number of
atoms of an element.
molar mass
A mole always contains the same number
of particles; however, moles of different
substances have different masses.
The Mass of a Mole
• 1 mol of copper and 1 mol of carbon have
different masses.
•Because !!!!
• One copper atom has a different mass than 1
carbon atom.
So same number of atoms, but different
masses. (ie 100 bricks or 100 feathers)
The Mass of a Mole (cont.)
• __________________ is the mass in
grams of one mole of any pure substance.
• The molar mass of any element is
numerically equivalent to its atomic mass and
has the units g/mol.
Using Molar Mass
• Moles to mass
Using Molar Mass (cont.)
• Convert moles to mass by multiplying by the molar
mass
• Convert mass to moles with the inverse molar mass
conversion factor. (1 / molar mass)
• Convert moles to atoms with Avogadro’s number as the
conversion factor.
• Convert atoms to moles with the inverse of Avagadro’s
number (1 / Av. #)
MOLE MOUNTAIN
Section 10.3 Moles of Compounds
• Recognize the mole relationships shown by a
chemical formula.
• Calculate the molar mass of a compound.
• Convert between the number of moles and mass of
a compound.
• Apply conversion factors to determine the number of
atoms or ions in a known mass of a compound.
representative particle: an atom, molecule, formula
unit, or ion
Section 10.3 Moles of Compounds
(cont.)
The molar mass of a compound can be
calculated from its chemical formula
and can be used to convert from mass
to moles of that compound.
Chemical Formulas and the Mole
• Chemical formulas indicate the numbers
and types of atoms contained in one unit of
the compound.
• One mole of CCl2F2 contains one mole of C
atoms, two moles of Cl atoms, and two moles
of F atoms.
The Molar Mass of Compounds
• The molar mass of a compound equals
• the molar mass of each element,
multiplied by the moles of that element
in the chemical formula, added together.
• ie: mass of H2O = mass of 2 moles of H +
mass of 1 mole of O.
• The molar mass of a compound
demonstrates the law of conservation of
mass.
Converting Moles of a Compound to Mass
• For elements, the conversion factor is the
molar mass of the element.
• The procedure is the same for compounds,
except that you must first calculate the molar
mass of the compound.
Section 10.4 Empirical and Molecular Formulas
• Explain what is meant by
the percent composition
of a compound.
• Determine the
empirical and molecular
formulas for a
compound from mass
percent and actual
mass data.
percent by mass: the
ratio of the mass of each
element to the total
mass of the compound
expressed as a percent
percent composition
empirical formula
molecular formula
A molecular formula of a compound is
a whole-number multiple of its
empirical formula.
Percent Composition
• The percent composition by mass of any
element in a compound can be found by
dividing the mass of the element by the
mass of the compound and multiplying by
100.
Percent Composition (cont.)
• The percent by mass of each element in a
compound is the ____________________
of a compound.
• Percent composition of a compound can also
be determined from its chemical formula.
Empirical Formula
• The _____________________________
for a compound is the smallest wholenumber mole ratio of the elements.
• The empirical formula may or may not be the
same as the molecular formula.
Molecular formula of hydrogen peroxide = H2O2
Empirical formula of hydrogen peroxide = HO
Molecular Formula
• The _______________________ specifies
the actual number of atoms of each
element in one molecule or formula unit of
the substance.
• Molecular formula is always a whole-number
multiple of the empirical formula.