OBJECTIVE

SWBAT calculate molar mass and use it to
convert between grams and moles.
MOLAR MASS

Number of grams in 1 mole

Equal to the numerical value of the atomic mass
1 mole of C atoms
=
1 mole of Mg atoms
=
1 mole of Cu atoms
=
2
MOLAR MASS

Number of grams in 1 mole

Equal to the numerical value of the atomic mass
1 mole of C atoms
=
12.011 g
1 mole of Mg atoms
=
24.305 g
1 mole of Cu atoms
=
63.546 g
3
LEARNING CHECK
Give the molar mass
A. 1 mole of Br atoms
=
________
B. 1 mole of Sn atoms
=
________
4
SOLUTION
Give the molar mass to 0.1 g
A. 1 mole of Br atoms
=
79.904 g/mole
B. 1 mole of Sn atoms
=
118.71 g/mole
5
MOLAR MASS OF COMPOUNDS
Mass in grams of 1 mole equal numerically to the
sum of the atomic masses
1 mole of CaCl2
=
1 mole of N2O4
=
6
MOLAR MASS OF COMPOUNDS
Mass in grams of 1 mole equal numerically to the
sum of the atomic masses
1 mole Ca x 40.078 g/mole
+
2 moles Cl x 35.453 g/mole
1 mole of CaCl2
= 110.984 g/mole
2 moles N x 14.007 g/mole
+ 4 moles O x 15.999 g/mole
1 mole of N2O4
= 92.01 g/mole
7
LEARNING CHECK
A. 1 mole of K2O
B. 1 mole of antacid Al(OH)3
= ______g
= ______g
8
SOLUTION
A. 1 mole of K2O
= 94.195 g
2 K x 39.098 g/mol
+ 1 O x 15.999 g/mol
B. 1 mole of antacid Al(OH)3
= 78.0027 g
1 Al x 26.982 g/mol
3 O x 15.999 g/mol
+ 3 H x 1.0079 g/mol
9
MOLAR MASS CALCULATION:
Prozac, C17H18F3NO, is a widely used
antidepressant that inhibits the uptake of
serotonin by the brain. It has a molar mass of
A) 62.0229 g/mole
B) 296. 56 g/mole
C) 309.3292 g/mole
10
SOLUTION
Prozac, C17H18F3NO, is a widely used antidepressant
that inhibits the uptake of serotonin by the brain. It has
a molar mass of
C) 309.0292 g/mole
17C (12.011)
+18H (1.0079)
+3F (18.998)
+1N (14.007)
+1 O (15.999)
11
MOLAR MASS FACTORS
Methane CH4 known as natural gas is
used in gas cook tops and gas heaters.
Express the molar mass of methane in the
form of conversion factors.
Molar mass of CH4 =
16.0426 g CH4
1 mole CH4
CH4
OR
16.0426 g/mol
1 mole CH4
16.0426 g
12
LEARNING CHECK
Acetic acid CH3COOH is the acid in vinegar . It has a
molar mass of approximately 60.0 g/mole.
1 mole of acetic acid =
mole acetic acid
g acetic acid
or
____________
g acetic acid
mole acetic acid
13
SOLUTION
Acetic acid CH3COOH is the acid in vinegar . It
has a molar mass of 60.0 g/mole.
1 mole of acetic acid
acid
1 mole acetic acid
60.0 g acetic acid
=
or
60.0 g acetic
60.0 g acetic acid
1 mole acetic acid
14
CALCULATIONS WITH MOLAR MASS
molar mass
Grams
Moles
15
MOLES-GRAMS FOR COMPOUNDS:
The artificial sweetener aspartame (NutriSweet) formula C14H18N2O5 is used to
sweeten diet foods, coffee and soft drinks.
How many moles of aspartame are present in
225 g of aspartame?
16
SOLUTION
Given: 225 g aspartame
Find: mol aspartame
Factor: _____ molar mass of aspartame = 1 mol aspartame
Molar mass of Aspartame C14H18N2O5
(14 x 12.011) + (18 x 1.0079) + (2 x 14.007) + (5 x 15.999)
= 294.3052 g/mole
Setup:
225 g aspartame x 1 mole aspartame
1
294.3052 g aspartame
= 0.7645 mole aspartame
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LET’S START DRAWING OUR MOLAR MAP!!!
Mass (g)
Mole
Particles
Ions
Atoms
Molecule
Formula Unit
Molar Mass
The molar mass of a compound is found by adding
Together the molar masses of all of its elements, taking
Into account the number of moles of each element present.
Let’s try using the mole and molar mass………………..
MOLES – GRAMS FOR ELEMENTS:
Aluminum is often used for the structure of
light-weight bicycle frames. How many
grams of Al are in 3.00 moles of Al?
3.00 moles Al
? g Al
20
Given: 3 mol Al
Find: g of Al
Factor: 1 mol Al = 27.0 g Al
27.0g Al
1 mol Al
Setup:
or
1 mol Al
27.0 g Al
3.00 moles Al x
Answer
27.0 g Al
1 mole Al
= 81.0 g Al
21
MOLES – GRAMS FOR ELEMENTS:
How many moles are in 22 g
Sulfur?
22 g S
? mol S
22
Given: 22 g S
Find: mol of S
Factor: 1 mol S = 32.0 g S
32.0g S
1 mol S
Setup:
or
22 g S
Answer
1 mol S
32.0 g S
x
1 mol S
32 g S
= 0.688 g S or 6.88x10-1 g S
23