CHEMICAL FORMULAS AND REACTIONS OF MATTER
CHEMICAL FORMULAS
We
use a chemical formula to save time and space in writing about chemistry. For
example, instead of writing “magnesium chloride contains one atom of magnesium
and two atoms of chlorine”, we simply write MgCl2. “The hydrogen
molecule contains two atoms of hydrogen is simply written as H2”.
Therefore a chemical formula consists of a symbol; or group of symbols with
proper subscripts, representing one molecule of an element or a compound.
Valence and Oxidation Number
Valence is defined as the number of
electrons one atom may gain or lose in completing its shell when it combines
with another atom. Therefore it is the combining capacity of an atom in a
compound. For example, the valence of magnesium is =2, while chlorine is -1.
Another related term to valence is the oxidation
number that is the positive and the negative charges that gives an
indication of how electrons are arranged in the compound. The oxidation number
of magnesium is +2 and of chlorine is -1, so we can use valence and oxidation
number interchangeably.
LIST OF CATIONS
1.
Cations
with fixed oxidation number +1
Name Symbol
Hydrogen H+
Lithium ion Li+
Sodium ion Na+
Potassium ion K+
Rubidium ion R b+
Cesium ion Cs+
Silver ion Ag+
Ammonium NH4+
2.
Cations
with fixed oxidation number of +2
Name
Symbol
Beryllium ion Be+2
Magnesium ion Mg+2
Calcium ion Ca+2
Strontium ion Sr+2
Barium ion Ba+2
Radium ion Ra+2
Zinc ion Zn+2
3.
Cations
with fixed oxidation number of +3
Name Symbol
Aluminum ion Al+3
4.
Cations
with variable oxidation numbers
A.
Cations
with oxidation number of +1 and +2
Name Symbol
Copper (I); copper (II) Cu+1; Cu+2
Mercury (I); mercury
(II) Hg+1; Hg+2
B.
Cations
with oxidation of +2 and +3C
Name Symbol
Chromium (II); chromium
(III) Cr+2; Cr+3
Cobalt
(II); cobalt (III) Co+2;
Co+3
Iron
(II); iron (III) Fe+2;
Fe+3
Manganese (II);
manganese (III) Mn+2; Mn+3
Nickel (II); nickel
(III) Ni+3;
Ni+3
C.
Cations
with oxidation of +2 and +4
Name Symbol
Lead (II); lead
(IV) Pb+2;
Pb+2
Tin
(II); tin (IV) Sn+2;
Sn+4
D.
Cations
with oxidation number of +3 and +5
Name Symbol
Arsenic
(III); arsenic (V) As+3; As+5
Antimony
(III); antimony (V) Sb+3;
Sb+5
Bismuth
(III); bismuth (V) Bi+3;
Bi+5
LIST OF ANIONS
1.
Anions
ending in ide
Name Symbol Names Symbol
Arsenide As- nitride N-3
Bromide Br- Oxide O‑2
Chloride Cl‑ Peroxide O2-2
Cyanide CN‑ phosphide P‑3
Fluoride F‑ Selenide Se‑2
Hydride H‑ Sulfide S‑2
Hydroxide HO‑ telluride Te‑2
2.
Anions
ending in ite
Name Symbol Name Symbol
Bisulfite HSO3‑ nitrite NO2-
Chlorite CLO2- sulfite SO3‑2
hypobromite BrO- phosphate PO3‑3
hypoclorite ClO‑
3.
Anions
ending in ate
Name Symbol Name Symbol
Acetate CH3COO or Manganate MnO4‑2
C2H3O2
Bicarbonate HCO3‑ Nitrate NO3‑
Bisulfate HSO4‑ Oxalate C2O4‑2
Borate BO3-3 Perchlorate CIO4-
Bromate BrO3‑ Permanganate MnO4‑
Carbonate CO3-2 Phosphate PO4‑3
Chlorate ClO3‑ Sulfate SO4‑2
Chromate CrO4‑2 Tetraborate B4O7‑2
Dichromate Cr2O7‑2
NAMING
INORGANIC COMPOUNDS
Compound maybe classified into binary
and ternary. Binary compounds are compounds containing 2 atoms while ternary
compounds contain more than 2 kinds of atoms.
I. Binary Compounds
1.
In naming compounds containing two
non-metals, the following rules are considered
a. Greek
prefixes are used in indicating the number of subscript of the atom.
Examples
Chemical formula Name
CO2 carbon
dioxide
N2O3 dinitrogen
trioxide
Greek Prefixes No. of Atoms
Mono 1
Di 2
Tri 3
Tetra 4
Penta 5
Hexa 6
Hepta 7
Octa 8
Nona 9
Deca 10
b. Mono
is used for the second element only
Examples
Chemical formula Name
CO carbon
monoxide
N2O
dinitrogen monoxide
c. The
last letter “a” or “o” is dropped when the Greek prefix is attached with
the second element staring with a
towel.
Examples
Chemical
formula Name
P2O5 diphosphorus pentoxide
Cl2O7 dichlorine
heptoxide
d. The
following formulas are commonly known and the rules mentioned above may not
apply.
Examples
Chemical formula Name
H2O water
PH3
phosphene
NH3 ammonia
N2H4 hydrazine
2. Binary compounds containing cations with
fixed oxidation number are named by giving first the name of the cation
followed by the name of the anion.
Examples:
Chemical
formula Name
MgBr2 magnesium
bromide
Ca3N2 calcium
nitride
Al2S3 aluminum
sulphide
AlP aluminum
phosphide
SrI2 strontium
iodide
Examples:
Chemical
formula Name
FeCl2 iron
(II) chloride
FeCl3 iron
(III) chloride
PbI2 lead
(II) iodide
PbI4 lead
(IV) iodide
However,
an old method can also be used. This is done by using suffix-ous to indicate
lower oxidation number, while suffix-ic is used to indicate higher oxidation
number.
Examples:
Chemical
formula Name
FeCl2 ferrous
chloride
FeCl3 ferric
chloride
PbI2 plumbous
iodide
PbI4 pumbic
iodide
Examples:
Chemical
formula Name
HCl hydrogen
chloride
H2S hydrogen
sulphide
HI hydrogen
iodide
However,
in aqueous solution, the prefix hydro
is followed by the name of the non-metal ending in ic and the word acid.
Examples:
Chemical
formula Name
HCl (aq) hydrochloric
acid
H2S (aq) hydrosulfuric
acid
HI (aq) hydroiodic
acid
5. For
binary metalloid compounds, the Roman numeral system or Greek prefix system may
be used.
Examples:
Chemical
formula Name
AS2S3 diarsenic
trisullfide or arsenic (III) sulphide
SiO2 silicon dioxide or silicon (IV) sulphide
II. Ternary Compounds
Examples:
Chemical formula Name
NaNO3 sodium
nitrate
Mg(NO2)2 magnesium
nitrate
CaSO4 calcium
sulfate
Ag2SO3 silver
sulfite
Examples:
Chemical formula Name
Fe(ClO3)2 iron(II)
chlorate
Fe(ClO3)3 iron(III)
chlorate
Sn3(PO3)2 tin(II)
phosphite
Sn3(PO4)4 tin(IV)
phosphate
However, an old method can also be used.
This is done by using suffix-ous to indicate lower oxidation number, while
suffix-ic is used to indicate higher oxidation number.
Examples:
Chemical formula Name
Fe(ClO3)2 ferrous
chlorate
Fe(ClO3)3 ferric
chlorate
Sn3(PO3)2 stannous
phosphite
Sn3(PO4)4 stannic
phosphate
Examples:
Chemical formula Name
H2SO3 hydrogen
sulphite
H2SO4 hydrogen
sulfate
HNO2 hydrogen
nitrite
HNO3 hydrogen
nitrate
However, in aqueous solution, the world
hydrogen is dropped and suffix-ite is
replaced by ous while the suffix-ate with ic followed by the word acid
Examples:
Chemical formula Name
H2SO3(aq) sulfurous
acid
H2SO4(aq) sulfuric acid
HNO2(aq) nitrous
acid
HNO3(aq) nitric
acid
4. Hydrates
are named by combining the Greek prefix with the Roman numeral.
Examples:
Chemical formula Name
CuSO4.5H2O Copper
(II) sulphate pentahydrates
Copper
(II) sulphate 5-water
For hydrates with only one unit of water
in a formula unit of salt, the word hydrate is used without the number.
Examples:
Chemical
formula Name
Ba(BrO3)2.H2O barium bromate
hydrate
WRITING CHEMICAL FORMULAS
The
following are guidelines in writing chemical formulas.
Examples
Name Chemical formula
Sodium chloride NaCl
Potassium
hydroxide KOH
Note that there is no charge shown in
the formula.
Aa Bb become
AbBa
Examples
a.
Aluminum Sulfide
Al+3 S-2 become Al2S3
b.
Calcium nitride
Ca+2 N-3 become Ca3N2
Note: No charge
appears in the formula because the charges are neutralized (net charge equals zero).
Examples
a.
calcium sulfide
Aa+2 S-2 become CaS
b. aluminum phosphide
Al+3 P-3 become AIP
4. One
as subscript should not be written.
Examples
a.
magnesium fluoride
Mg+2 F-1 become MgF2
b.
Aluminum chloride
Al+3 Cl-1 become AlCl3
Examples
a. Lead (IV) oxide
Pb+4 O-2 become Pb2O4 and finally
become PbO2
b. Tin (II) sulfide
Sn+2 S-2 become Sn2S2 and finally become SnS
Examples
a.
calcium phosphate
Ca+2 PO4-3 become Ca3(PO4)2
b.
ammonium sulfate
NH4+1 SO4-2 become (NH4)2 SO4
CHEMICAL EQUATIONS
A
chemical equation is a shorthand method of representing chemical reaction using
chemical symbols and formulas to indicate the reactants and the products.
Chemical equation show:
1. The
reactants that enter in the chemical reaction.
2. The
products that are formed in the chemical reaction.
3. The
amount of each substance used and each substance produced.
2AgI + Na2S
→ Ag2S
+ 2NaI
Two important principles to remember
about chemical equations:
1. Every
compound has a formula which cannot be altered.
2. A
chemical reaction must account for every atom that is used. This is an
application of the Law of Conservation of Mass which states that in chemical
reaction atoms are neither created nor destroyed.
Symbols used in chemical equations:
1. → - means to
produce, to form
2. ⇌ - means the reaction is reversible
3. +
- means a substance is added to or reacting with other
substances
4. (g), (l), (s) –
when each is written after a chemical formula, describes the physical state of
the substance.
5. ↑ - means gas is
evolved
6. ↓ - means
precipitate is formed
7. - means heat is
applied
8. Catalyst
is written above the arrow
BALANCING SIMPLE TYPE OF CHEMICAL
EQUATIONS
Guidelines:
1. Write
the correct formula for the reactants and products.
2. Start
with the more complex part.
3. If
there is a free element, you balance it last.
4. For
reactions involving polyatomic ions, balance the ion as a group.
TYPES OF CHEMICAL REACTIONS
1. Combination Reaction – two
or more substance combine to form one product.
General
form: A + B → AB
Examples: 4Al(s) + 3O2(g) → 2Al2O3(s)
CaO(s)
+ SO2(g) → CaSO3(s)
2. Decomposition Reaction – a compound
decomposed to form two or more substances.
General
form: AB → A + B
Where
A & B are metals
Fe(s)
+ CuSO4(aq) → FeSO4aq)
+ Cu(s)
Zn(s)
+ MgSO4(aq) → no
reaction
Activity series
Li
K
Ba
Ca
Na
Mg
Al
Zn
Fe
Cd
Ni
Sn
Pb
H
Cu
Hg
Ag
Au
4.
Metathesis (Double Displacement Reaction) – the
positive ions exchange partners with the negative ions to form two new
compounds.
General
form: AX + BY → AY + BX
Examples: AgNO3(aq) + HCl(aq) → AgCl(aq) +
HNO3(aq)
Na2SO4(aq)
+ Pb(NO3)2(aq) + 2NaNO3(aq) + PbSO4(aq)
5. Neutralization Reaction
a. Acid
+ base → salt + water
b. Metal
oxide + acid → salt + water
c. Nonmetal
oxide + base → salt + water
6. Combustion Reaction –
reaction of elements and compounds with oxygen. It only takes place when there
is oxygen. The products of combustion are carbon dioxide, carbon monoxide, and
water only.
RECORDED LECTURES
How To Write Chemical Equations From Word Description
https://www.youtube.com/watch?v=npyvZSBqyc0
Balancing Chemical Equations Practice Problems
https://www.youtube.com/watch?v=eNsVaUCzvLA
Types of Chemical Reactions
https://www.youtube.com/watch?v=aMU1RaRulSo
ONLINE PUBLISHED RESEARCH
Redox reactions in food fermentations
https://doi.org/10.1016/j.cofs.2018.03.004.
(http://www.sciencedirect.com/science/article/pii/S2214799317301030)
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