Download Honors Chemistry Chapter 10 Student Notes

Honors Chemistry
Chapter 10 Notes – Chemical Quantities
(student’s edition)
Chapter 10 problems:
Chapter 10 Diagrams:
10.1
48, 60-62, 72, 74, 76, 77, 80, 81
6, 7, 9-12
The Mole: A Measurement of Matter
Stoichiometry : The study of the
.
Formula Mass : The sum of the
.
When calculating the atomic masses, round the periodic table mass to the nearest
!
Atomic masses are measured in amu.
Ex1
H2
Ex2
H2O
Ex3
Ca(OH)2
Molecular mass - same thing, but truly used for
only.
Gram Atomic Mass and Gram Formula Mass: Same thing as above, but the unit is
ex - H2O
formula mass (or molecular mass)
gram formula mass
=
=
(also called gram molecular mass - also called gram atomic weight)
.
The Mole: The amount of a compound or element that contains
that substance.
Atoms are tiny, so we count them in “
A mole is a “
”.
”.
1 mole = 1 gram formula mass =
Element
Na
O2
HCl
NaCl
10.2
particles of
particles
Moles Atoms/Molecules/Formula Units
1
atoms
1
molecules
1
molecules
1
formula units
Mass
grams
grams
grams
grams
Mole-Mass and Mole-Volume Relationships
For starters in chemistry, we have to be able to convert between moles, grams, and
molecules/atoms of substance (also liters when we work with gases).
The “mole map”:
The Gram House
The Mole House
The Particle House
Use the Ptable to determine
the number of grams
Always a value of:
Always a value of:
1.0 Mole
The House of Volume
For gases, use 22.4 Liters at
Standard Temperature and
Pressure (STP)
Ex1
convert 13.8 g Li to moles
6.02 x 1023 atoms or
molecules
10.3
Ex2
convert 2.0 moles Ne to g
Ex3
convert 3.0 moles of Be to atoms
Ex4
convert 44.8 L of O2 to moles
Ex 5
convert 128 g of O2 to molecules of O2
Ex6
convert 128 g of O2 to atoms of oxygen
Ex7
If there are 9.71 x 1024 atoms of oxygen in a sample of SO3, how many grams of
SO3? liters?
Percent Composition and Chemical Formulas
Percentage Composition: Every compound has a certain percentage of each type of atom.
We measure the percentages by mass.
% composition = (mass of element/ mass of compound)
x
100
Ex1
Calculate the percent composition if a compound contains 24 g of Carbon and
64 g of Oxygen.
Ex2
What is the percentage composition of each element in Ba(OH)2
Determining a compound’s empirical and molecular formula:
Empirical Formula: the
(
)
whole number ratio of atoms in a compound
Three basic steps:
1. Divide (%’s or grams) by the gram atomic mass
2. Divide the resulting #’s by the smallest of those numbers
3. Multiply by 2 or 3 only if a whole number ratio isn’t the result of step 2
Ex1
Calculate the empirical formula if there is 52.17 % C, 13.04% H, and 34.78 % O.
Ex2
Calculate the empirical formula if there is 26.56 % K, 35.41 % Cr, and 38.03 % O.
Ex3
Find the empirical formula if a sample contains 5.6 g N and 12.8 g O.
sometimes , the information provided isn’t always the same…
Ex4
An unknown compound decomposes into 1.134 g of I2(s), and 100.0 cm3 H2. Find
the empirical formula.
Finding Molecular Formulas:
The same steps as empirical formula with one additional step - use the gram
formula mass of the empirical formula and its relationship to the gram formula
mass of the molecular formula to find what number to multiply the empirical
formula by to find the molecular formula (sounds more complicated than it is).
Ex5 - Find the molecular formula of a compound (mw = 144.0 g) with 66.67 % C,
11.11 % H, and 22.22 % O