Transcript Slide 1
Section 10.1 (Continued)
THE MOLE (II)
The Mass of a Mole of an
Element
Because every sample of matter we deal with
contains a large number of atoms, it is easier
to talk about the mass of the sample in terms
of grams of atoms.
Gram atomic mass (gam) – the mass of one
mole of atoms of an element in grams
Gram Atomic Mass
1 mole Carbon atoms =12.01g
1 mole Hydrogen atoms =1.01g
1 mole Sulfur atoms = 32.07g
1 mole Iron atoms= 55.85g
Where can we find these values?
Periodic Table – atomic mass
Atomic mass = mass of a single atom, units are
amu
ADD THIS TO YOUR NOTES!!!
Periodic tables are INCONSISTENT
We will round the mass to TWO decimal
places.
These are constant, and do not affect sig figs.
What is true about the number of atoms in
each of these samples?
12.01 g carbon or 16.00 g oxygen
Each has 6.02 x 1023 atoms in the sample
The Mass of a Mole of a
Compound
We have been talking about the mass of a
mole of atoms.
What would we need to know to find the
mass of a mole of a compound?
Formula
# of atoms of each element in the compound
SO3
SO3 is composed of :
1 atom of Sulfur
3 atoms of Oxygen
We calculate the mass of a mole of compound
just like we calculate the mass of a single
molecule
For example…
You can calculate the mass of a SO3 molecule
by adding the atomic masses of the atoms that
make it up.
Atomic mass of S = 32.07 amu
Atomic mass of O = 3 x 16.00 amu = 48.00 amu
Multiply by 3 because we have 3 oxygen atoms
Molecular mass of SO3
32.07 amu + 48.00 amu = 80.07 amu
16.00 amu
16.00 amu
32.07 amu
16.00 amu
Gram molecular mass (gmm) – the mass of 1
mole of a molecular compound in grams
Find this by substituting g for amu
1 mole of SO3 has a gmm of 80.07 g
Find this by adding together the mass of each
atom in the compound
Find the gram molecular mass of
the following compounds:
Glucose (C6H12 O6 )
6(12.01g C) + 12 (1.01 g H) + 6(16.00 g O) = 180.18 g
C6H12 O6
Water (H2 O)
2(1.01g H) + 1 (16.00 g O) = 18.02 g H2 O
What is the mass in grams of 1 mole of
hydrogen peroxide (H2 O2 )?
1 mole H2 O2 has a mass of:
2(1.01 g H) + 2(16.00 g O) = 34.02 g H2 O2
What is the mass of 1 mole of each
substance?
Chlorine gas
2(35.45 g Cl2) = 70.90 g Cl2
Nitrogen Dioxide
14.01 g N + 2(16.00 g O) = 46.01 g NO2
Carbon Tetrabromide
12.01 g C + 4(79.90 g Br) = 331.61 g CBr4
Silicon Dioxide
28.09 g Si + 2(16.00 g O) = 60.09 g SiO2
Gram Formula Mass
For Ionic compounds, the representative
particle is a formula unit- not a molecule, so
we can’t use gmm
Gram formula mass (gfm) - the mass of one
mole of an ionic compound in grams
This is calculated the same way as the gram
molecular mass
Ex. 1 mole of Calcium Iodide CaI2 has a gfm of
40.08g Ca + 2(126.90 g I) = 293.88 g CaI2
What is the gram formula mass of single
formula unit of ammonium carbonate?
(NH4)2CO3
N = 2(14.01) = 28.02
H = 8(1.01) = 8.08
C = 1(12.01) = 12.01
O = 3(16.00) = 48.00
Total gfm = 96.11 amu
Terminology
These terms mean the same thing:
Formula weight
Molecular weight
Molar mass
Gram atomic mass
Gram formula mass
Gram molecular mass
THESE ALL MEAN THE MASS OF ONE MOLE OF
A SUBSTANCE!!!!