Admin_chemistry-4-chemistry-an-atoms-first-approach-zumdahl-atoms-1st-590-ch-5-stoichiometry-21696.p

CHEMISTRY - ZUMDAHL ATOMS 1ST 3E
CH.5 - STOICHIOMETRY

CONCEPT: CALCULATING MOLAR MASS
● Molar Mass is a physical property that represents the mass of a substance divided by the amount of that substance.
□ The SI units for mass is kg and the amount of substance is moles, but molar mass is in __________.
□ Molar mass is also referred to as ______________ weight, ______________ weight or ______________ mass.
STEP 1: Count the number of each element within the given compound.
□ If elements are within parentheses, just remember to distribute the subscript to each element.
STEP 2: Find the atomic masses of each element from the Periodic Table.
STEP 3: Multiply together the number of each element with their atomic masses from the Periodic Table.
STEP 4: Add up the totals after multiplication to determine the molar mass of the compound.
Molar Mass Formula
Molar Mass =
_______ N _______ S
_______ H _______ O
(NH
4
)
2
SO
4
1
H
Hydrogen
1.008
7
N
Nitrogen
14.01
8
O
Oxygen
16.00
16
S
Sulfur
32.07
___ N x 14.01 g/mol = _______ g/mol
___ H x 1.008 g/mol = _______ g/mol
___ S x 32.07 g/mol = _______ g/mol
___ O x 16.00 g/mol = _______ g/mol
EXAMPLE: Calculate the molar mass of the compound (NH
4
)
2
SO
4
.
CHEMISTRY - ZUMDAHL ATOMS 1ST 3E
CH.5 - STOICHIOMETRY
Page 2

CONCEPT: CALCULATING MOLAR MASS
PRACTICE: Calculate the molecular weight of C
3
H
5
N
3
O
3
.
PRACTICE: The reaction between nickel metal and hydrochloric acid is not a simple dissolution. The product formed is
NiCl
2
·
6 H
2
O (s), nickel (II) chloride hexahydrate, which has exactly 6 waters of hydration in the crystal lattice for every
nickel ion. What is the molar mass of nickel (II) chloride hexahydrate, NiCl
2
·
6 H
2
O (s)?
PRACTICE: What is the molar mass of diazepam also known as Valium if 0.05570 mol weighs 15.86 g?
CHEMISTRY - ZUMDAHL ATOMS 1ST 3E
CH.5 - STOICHIOMETRY
Page 3

CONCEPT: MOLE CONCEPT
The Mole
● The mass of substance “containing the same number of units as atoms in 12.00 g of Carbon-12” and connects together:
□ Atom : A single element with no charge.
□ Ion : A single element with ______ or ______ charge.
□ Molecule : A compound with 2 or more ____________ together.
□ Formula Unit : General term for a compound composed of a(n) __________ and __________.
Converting between Moles and Particles
● Avogadro’s Number : One mole of a substance is equal to __________________ particles .
□ Particles: A general term that is used for ions, atoms, molecules or formula units.
□ 1 mole of chlorine, Cl
2
, equals 6.022 x 10 23 molecules Cl
2
.
______________
Converting between Mass and Moles
● One mole of a substance is equal to the molar mass of that substance.
□ 1 mole of chlorine, Cl
2
, weighs 70.90 grams.
______________
EXAMPLE: Which of the following compounds would not be associated with the term “formula unit”?
a) Na
2
CO
3
b) CH
3
COONa c) BF
3
d) MnCl
4