1. Formulas and Equations
Topic 2
Formulas and Equations

2. Topic 2 Outline-Formulas and Equations
Chemical Symbols and Formulas
a. Diatomic elements vs. Monatomic elements
b. Empirical formulas
c. Molecular formulas
Polyatomic Ions (PAIs)-Table E
Hydrates
Names  Formulas
Formulas  Names
Reactions
a. Reactants vs. products
b. Exothermic vs. endothermic (Table I)
c. Balancing-can only change coefficients
Types of Reactions
a. Synthesis (Direct Combination)
b. Analysis (Decomposition
c. Single Replacement
d. Double Replacement
e. Combustion
i. Incomplete
ii. Complete
Conservation of Mass

3. Elements that when alone; not in a compound, appear as a single atom
Monatomic Elements-
Elements that when alone; not in a compound, appear as a single atom
ex. Cu, Zn, V, C
Diatomic Elements-
Elements that when alone; not in a
compound, appear as a pair
ex. Br2 I2 N2 Cl2 H2 O2 F2
To remember the diatomic elements; think
Mr. BRINCLHOF

4. A formula with the lowest whole-number ratio of elements in a compound
Definitions to know
Empirical Formula-
A formula with the lowest
whole-number ratio of elements in
a compound
Ex. The empirical formula of hydrogen peroxide is:
H2O2  HO
Molecular Formula-
A chemical formula of a molecular compound that shows the kinds and numbers of atoms present in a molecule of a compound
Ex. The molecular formula of glucose is
C6H12O6

5. So…based on what we know, if the molecular formula of benzene is C6H6,
what is its empirical formula? CH
If the molecular formula of glucose is
C6H12O6, what is its empirical formula?
CH2O
In some cases, the molecular and empirical formula can be the same

6. Polyatomic Ions (PAIs) Reference Table E
A tightly bound group of atoms that behave as a unit and has a positive or negative charge
Ex: NH4+ or SO4-2
Hydrate
A compound that has a specific number of water molecules bound to each formula unit .
  CuSO4
5H2O
The dot is NOT a multiplication sign but is there to
tell you that for every one CuSO4, there are 5 water
molecules trapped within it.

7. Must find part or all on Table E
There are two types of compounds: 1. Binary-composed of 2 elements 2. Ternary-composed of 3 or more elements
Binary Compounds
Ternary Compounds
End in “ide”
Must find part or all on Table E
End in “ate” or “ite”
Watch for the exceptions:
OH- = hydroxide
CN- = cyanide
O22- = peroxide

9. Stock System
IUPAC System-International Union of Pure and Applied
Chemistry I
Used for molecular and ionic compounds with metal having multiple oxidation numbers
After the name of the first element, write the oxid # in ( ), using Roman numerals
Ex. FeCl3-iron (III) chloride
CuSO4-copper (II) sulfate
Sb(NO2)5-antimony (V) nitrite

10. Contains 2 nonmetals or semi-metal and nonmetal
Molecular System
Contains 2 nonmetals or semi-metal and nonmetal
The prefix tells the number of atoms in the molecule. Prefix both atoms (except when there is only one atom in the first named element)
Prefix- mon(o) -1
di – 2
tri – 3
tetr(a) – 4
pent(a) – 5
hex(a) – 6
hept(a) -7
oct(a) – 8
non – 9
dec - 10

11. Rules for Naming Binary Ionic Compounds
Ionic Binary Compounds-
Contain metal /nonmetal
Name of the element with the + oxidation # (or lowest
ionization energy (IE), or cation, or metallic ion) is
placed first.
-for those with only one oxidation #, the name
is unchanged
-for those with multiple oxidation #s, use the
stock System (Roman numerals) to express
which oxidation # is involved
Name of the element with the – oxidation # (or
highest IE or anion or nonmetallic ion) is
placed last with the name modified to end in
“ide”
3. Criss-cross apple sauce

12. Ternary Ionic Compounds
Ternary Ionic Compounds-Contain element with a PAI (table E) or 2 PAIs
If the element is the + oxid #, place it first, follow
the rules before for multiple oxid. #s, place – PAI
last, do not modify the name
If the PAI is the + oxid #, place it first, place the – element last and modify to end in “ide”
If 2 PAIs, place the + first, - last and simply say both
names
4. Criss cross apple sauce

13. (Contain two nonmetals or semi-metal with nonmetal)
Molecular Compounds
(Contain two nonmetals or semi-metal with nonmetal)
Place the element with the lowest IE (+ oxid #) first, the element with the highest IE (- oxid # last) and modify to
end in “ide”
Name using the Stock System or prefix system.
Ex. N2O-
Nitrogen (I) oxide or dinitrogen monoxide
SO3-
Sulfur (VI) oxide or sulfur trioxide
GeBr4-
Germanium (IV) bromide or germanium
tetrabromide
If using prefixes…no criss cross

14. Exothermic Reaction-a reaction that releases heat to its environment
Writing Equations
2 ways to write equations:
1. With the energy term within the equation
2. With the energy term outside the equation
Exothermic Reaction-a reaction that releases heat to its environment
In eq:
Reactants  Products + heat or
Reactants  Products H
Outside eq:

15. Endothermic Reaction-a reaction that absorbs
heat from the surroundings
In eq: reactants + heat  products or
Outside eq: reactants  products H
Look at Reference Table I

17. Be careful when using Table I
Sometimes they want to know the amount of energy
gained or released when the number of moles differs
from the equation given on the chart
Ex.: 4Al(s) + 3O2(g)  2Al2O3(s)
H = kJ
How much energy/heat is released when one mole of
aluminum oxide is produced?
The chart shows 2 moles forming so we would have to
half the amount to correspond to one mole ( kJ)

18. Each side of the equation has the same number of ATOMS
Balancing Equations
Each side of the equation has the same number of ATOMS
of each element and mass is conserved
Rules
Determine the correct formula for all the reactants and products
Write the skeletal equation by placing the formulas for
the reactants on the left and the formulas for the products on the right with a yields sign () in between. If two or more reactants or products are involved, separate their formulas with a plus sign
Determine the number of atoms of each element in the
reactants and products. Count PAIs as a single unit if it appears unchanged on both sides of the equation

19. Balance the elements one at a time by using
coefficients. When no coefficient is written, it is
assumed to be 1. Begin by balancing elements
that appear only once on each side of the equation.
Never balance an equation by changing the subscripts in a chemical formula. Each substance has only one correct formula
Check each atom or PAI to be sure that they are
equal on both sides of the equation
Make sure all the coefficients are in the lowest
possible ratio.
Balancing Chemical Equations

20. Types of Reactions
1. Synthesis/Direct Combination
2. Analysis/Decomposition
3. Single Replacement Reaction
4. Double Replacement Reaction
5. Combustion
Incomplete
Complete
Oxidation-Reduction
This is a separate unit

21. Synthesis/Direct Combination
General Formula:
A + B  AB
**only one product is produced
Ex:
H2 + O2  H2O
KCl + O2  KClO3
Fe + S  FeS

22. Analysis/Decomposition
General Formula:
AB  A + B
**notice only one reactant
Ex:
H2O2  H2O + O2
CaCO3  CaO + CO2
Al(OH)3  Al2O3 + H2O

23. Single Replacement Reaction
General Formula:
C + DE  E + DC
A + BC  AC + B or
C and E are nonmetals
A and B are metals
Metals only replace metals
Nonmetals only
replace nonmetals
Notice elements and a compound are forming a new element and a new compound
The question asked about single replacement reactions is:
Do they work?
How do you know?
Check Table J

25. Table J lists the strengths of metals and nonmetals. The
strongest metals and nonmetals are towards the top of
Table J and the weakest are on the bottom.
You must check the strength of the element on Table J and
compare it to the strength of the element it is trying to
knock out. If the ELEMENT is stronger, the reaction works.
If the element is NOT stronger than the element it is trying
to knock out, it will not work.

26. Ex: Fe + HCl 
Does it work?
1. Find the element (Fe) on Table J.
Find the element in the compound (HCl) that is
is the same column as the element (Fe)
In this case, it is H
If the element is higher than the element in
the compound, the reaction works. Figure out
the new products.
If the element is lower than the element in
the compound, the reaction does not work
and write NR (no reaction)

27. ex: Mg + FeSO4 
Find Mg on Table J, then find Fe
Is Mg higher or lower than Fe?
Higher…then it works!!!!!
Answer:
Mg + FeSO4  Fe + MgSO4
NaCl + Br2 
Find Br on Table J, then find Cl
Is Br higher or lower that Cl?
Lower…then it doesn’t work!!!!
Answer: NaCl + Br2  NR (no reaction)

28. The question asked about double replacement
Double Replacement Reactions
General Formula:
AB + CD  AD + CB
The question asked about double replacement
reactions is:
Does it go to completion?
Goes to completion if one of three products is formed.
Precipitate (solid)-a solid that forms
and settles out of a liquid mixture-Table F-
it will be insoluble
2. Water (HOH)
3. Gas

29. H2O but will appear as HOH When HOH is a product, it is written as
You will need Table F to determine if it is a solid or not
Soluble-
Dissolves in water
NaCl (aq)
Insoluble-
Does not dissolve in water
AgCl(s)
In double replacement reactions, water will not appear as
H2O but will appear as HOH
When HOH is a product, it is written as
HOH (l)

30. (
(s)
(s)
(aq)
(aq)

31. NaCl (aq) + AgNO3 (aq) 
Ex:
1. Determine the products
Determine if the products either dissolve
in water, is it a gas or is it water
If one of the products is a solid, gas or
water, it goes to completion (GTC)
If both products dissolve in water, it
does not go to completion (DNGTC)
ANSWER:
NaCl (aq) + AgNO3 (aq) 
NaNO3 (aq) + AgCl (s)
A solid is formed so it does go to completion

32. Ex: NaCl (aq) + H2SO4 (aq)  HCl(aq) + Na2SO4 (aq)
Both products dissolve in water according
to Table F…does not go to completion
Ex: NaOH + HCl 
NaCl (aq) + HOH (l)
Notice the HOH…this is water…H2O
Also…notice the reactants do not have (aq) next to them.
chemists agree that all double replacement reactions take
place in water and therefore do not have to indicate it with
the (aq)

33. A chemical change in which an element or a compound
Combustion
A chemical change in which an element or a compound
reacts with oxygen, often producing energy in
the form of light and heat
2 types of combustion
1. Incomplete
2. Complete
Incomplete: fuel + oxygen  carbon monoxide + water
Ex: CH4 + O2  CO + H2O
Complete: fuel + excess oxygen  carbon dioxide + water
Ex: CH4 + O2  CO2 + H2O

34. conserved. Mass is neither created or destroyed,
Conservation of Mass
In any physical change or chemical reaction, mass is
conserved. Mass is neither created or destroyed,
Mass of reactants = Mass of products
2NaBr  2Na Br2
2( )  (2)(23)
(2)(103) 