Transcript The Mole: A Measurement of Matter

The Mole: A Measurement of Matter
Describe how Avogadro’s
number is related to a mole of
any substance
Solve problems involving mass
in grams, amount in moles, and
number of atoms of an element
The Mole and Avogadro’s Number
SI unit that measures the amount of
substance
1 mole = 6.022 x 1023 representative
particles
Representative particles are usually
atoms, molecules, or formula units
(ions)
Examples
Substance
Representative Chemical
Particle
Formula
Representative
Particles in
1.00 mol
Nitrogen
Atom
6.022 x 1023
N
atoms
Sodium
Atom
Na
6.022 x 1023
atoms
Calcium
Atom
Ca
6.022 x 1023
atoms
Solve
How many atoms are in one mole of
1. Mercury (Hg)
2. Gold (Au)
3. Silver (Ag)
4. Iron (Fe)
How many moles of magnesium are
in 1.25 x 1023 atoms of magnesium?
Divide the number of atoms or
molecules given in the example by
6.022 x 1023
Divide (1.25 x 1023) by (6.022 x 1023)
Express in scientific notation
Answer = 2.08 x 10-1 mol Mg
How many moles of silver, Ag, are in
3.01 x 1023 atoms of silver?
Answer
0.500 mol Ag
Molar mass
Mass (in grams) of one mole of a
substance
Broad term (can be substituted) for
gram atomic mass, gram formula
mass, and gram molecular mass
Can be unclear: What is the molar
mass of oxygen?
O or O2 ? - element O or molecular
compound O2 ?
Molar Mass
The mass of one mole of atomic
hydrogen is 1.01 grams.
The mass of one mole of aluminum is
26.98.
What is the mass of one mole of
barium? Zinc? Neon?
Calculating the Molar Mass
What is the mass in grams of 3.50
mol of the element copper?
1. Look up the mass on the periodic
table. Round it to two decimal
places. (63.55 g)
2. Multiply 63.55 g by 3.50 moles.
Answer is 222 g Cu (Three significant
figures because three figs in 3.50)
Solve
What is the mass in grams of 2.00
mol of nitrogen?
Solve
What is the mass in grams of 1.20 x 108
atoms of copper, Cu?
1. Convert the given amount of atoms to
the amount of moles by dividing by
Avogadro’s number.
Answer: 1.99 x 10-16
2. The amount in moles is then multiplied by
molar mass (63.55)
Answer: 1.27 x 10-14 g Cu