Hemet High • Honors Chemistry
7 ● Chemical Formulas and Chemical Compounds
NOTES
Section 1: Forming Ions
Review…

__________ are Groups 1A, 2A, and 3A and they have _____________ charges.

__________ are Groups 5A, 6A, and 7A and they have _____________ charges


They end in “ide”
Majority of elements in Groups ___ and ___ do not usually form ions.
Ions of Transition Metals

Some transition _________ in Groups 1B-8B form more than one cation with
___________ charges.

Example: _______ forms Fe2+ and Fe3+

Two methods of naming:

________ System: Iron (II) ion and Iron (III) ion

___________ name: Ferrous ion and Ferric ion
Common Metal Ions with More than One Ionic Charge *Look at hand-out
Other Transition Metal Ions

Some transition metals have only ____ charge and ______ use a Roman numeral.

Examples (Write on Periodic Table)

Silver: ______

Cadmium: _____

Zinc: _____
Polyatomic Ions
*Look at hand-out

The names of most polyatomic anions end in “_____” or “_____”

The “-ite” ending indicates one ____ oxygen atom than the “-ate” ending
Write the formula that will form between Ba and Cl
1. Write the positive ion of metal first, and then negative ion
Ba2+
Cl2. Do the charges equal zero? ______
3. Use Criss-Cross method – write subscripts  BaCl2
Examples
1. Na+
S2
_____________
3. Mg2+
N3
_____________
2. Al3+
Cl-

_____________
4. Al3+
S2-

_____________
Use the Criss-Cross Method to Write Formulas using the following:
Cl-
N3-
OH-
CO32-
PO43-
Na+
Ca2+
Al3+
NH4+
_________________:are composed of 2 elements & can be either ionic or molecular.
Naming Binary Ionic Compounds
 To name a binary ionic compound, place the _______ name first, followed by the
________ name. Remember the anion ends in “-_____”

Examples:
 Cs2O
_______________
NaBr
_______________


CuO
_______________
Naming Compounds with Polyatomic Ions

State the _______ first and then the _______ just as you did in naming binary ionic
compounds.

KNO3
________________

Mg(ClO2)2
________________
Naming Binary Molecular Compounds

Binary molecular compound: must be composed of two _____________

Use _________ to indicate the number and kind of atom in the compound
Use the following general format:
1st name: prefix + element name
2nd name: prefix + element name + “ide”
If there is only one of the 1st element, no prefix.
Examples: Name the following:


CO
________________

N2 O
________________

CO2
________________

Cl2O8
________________
Writing Formulas for Binary Molecular Compounds
 Use the __________ in the name to tell you the ______________ of each element in
the formula.

Then write the correct ______________ for the two elements with the appropriate
_______________. The least electronegative element is written first.
Dinitrogen Tetroxide - ____________
Examples
 Write formulas for the following:

Nitrogen Monoxide
________________

Carbon Tetrachloride
________________

Diphosphorous Pentoxide
________________
Naming Acids
 An acid is a compound that contains _____ or more ___________ atoms and
produces hydrogen ions (H+) when dissolved in water.

All acids begin with _______________

General Format: HnX

“X” represents a monatomic or polyatomic anion.

“n” represents the number of hydrogen ions
3 Rules for Naming Common Acids

If the name of “X” ends in -ate: ____________-ic acid

If the name of “X” ends in -ite: ____________-ous acid

If the name of “X” ends in -ide: hydro-__________-ic acid
Name these acids

H2SO4
________________

HCl
________________

H2S
________________

HNO3
________________

HClO2
________________
Writing Formulas for Acids
 If the acid ends in -ic, then “X” ends in -ate.

If the acid ends in -ous, then “X” ends in -ite.

If the acid has hydro-________-ic, then “X” ends in -ide.

The subscript on hydrogen is equal to the charge of “X”.
Write the Formula for the Following Acids

Hydrobromic Acid
________________

Carbonic Acid
________________

Phosphoric Acid
________________

Sulfurous Acid
________________
Homework: 7.1 page 251 #14, 15(a-d), 41
Section 3: Using Chemical Formulas
The Mass of a Mole of an Element
• Molar Mass: is the atomic mass of an element expressed in grams/mole (g/mol).
•
Carbon = _________ g/mol
•
When dealing with molar mass, round off to ____ decimals.
• 12.011g/mol  12.01g/mol
•
Hydrogen = __________ g/mol
The Mass of a Mole of a Compound
•
You calculate the mass of a molecule by ___________ the molar masses of the atoms
making up the molecules.
•
Example: H2O
• Molar Mass of H2O =
• This applies to both ____________ and ________________ compounds
•
Find the molar mass of PCl3
•
What is the molar mass of Sodium Hydrogen Carbonate (NaHCO3)?
Converting Moles to Mass
•
You can use the ______________ of an element or compound to convert between the
mass of a substance and the moles of a substance.
•
 # of moles   mass( g ) 

Mass (g) = 
 
1

  1 mole 
Example 1: If molar mass of NaCl is 58.44 g/mol, what is the mass of 3.00mol NaCl?
Example 2: What is the mass of 9.45 mol of Aluminum Oxide (Al2O3)?
Converting Mass to Moles
•
You can invert the conversion factor to find ______ when given the mass.
 mass( g )   1 mole 

Moles = 
 
1

  mass( g ) 
Example 1: If molar mass of Na2SO4 142.05 g/mol, how many moles is 10.0 g of
Na2SO4?
Example 2: How many moles are in 75.0 g of Dinitrogen Trioxide?
Percent Composition
•
Percent Composition: the relative amount of the elements in a compound.
•
Also known as the percent by _________
•
It can be calculated in ____ ways:
– Using Mass Data
– Using the Chemical Formula
% Composition from Mass Data
% mass of element= mass of element x 100%
mass of compound
•
Example: Percent Composition of K2CrO4
•
K = 40.3%, Cr = 26.8%, and O = 32.9%
•
The percents must total 100% or really close to it.
•
Key Fact: percent composition of a compound is always the same regardless of the
amount of compound present.
Example
• When a 13.60 g sample of a compound containing Mg and O is decomposed, 5.40 g O
is obtained. What is the % composition of this compound?
Mass of compound:
Mass of oxygen:
Mass of magnesium:
% Mg =
%O=
Find the percent composition of Cu2S.
•
Find mass of Cu and S
– Cu2 =
–S=
•
Find mass of Cu2S =
% Composition
% Cu =
%S=
Find the percentage by mass of water in the hydrate Na2CO3•10H2O
Homework: 7.3 page 253 #30-33
Section 4: Determining Chemical Formulas
Empirical Formulas
• Empirical Formula: shows the _____________ whole-number ratio of the atoms of the
elements in a compound.
•
Example:
– The EF for Hydrogen Peroxide (H2O2) is HO with a _____ ratio.
– The EF for Carbon Dioxide (CO2) is CO2 with a ______ ratio.
Determining the Empirical Formula of a Compound
• A compound is found to contain 25.9% Nitrogen and 74.1% Oxygen. What is the
Empirical Formula of the compound?
Molecular Formulas
• Molecular Formula: tells the _________ number of each kind of atom present in a
molecule of a compound
•
Example:
– The Molecular Formula for Hydrogen Peroxide is H2O2.
– The Molecular Formula for Carbon Dioxide is CO2
•
It is possible to find the ____________ Formula using the __________ Formula if you
know the molar mass of the compound.
Finding the Molecular Formula
• Calculate the molecular formula of a compound whose molar mass is 60.0 g/mol and
empirical formula is CH4N
• Step 1: Find the empirical formula molar mass
•
Step 2: Divide molar mass by EF molar mass and round to whole #.
•
Step 3: Multiply empirical formula by the answer from Step 2.
Homework: 7.4 page 253 #36-38