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8/7/2019 Kimia Bab 3

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CHAPTER 3

Nomenclature and Chemical Reaction Equation

By : Putri Ardiana Puspita Sari (X-8/29)


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Chemical Nomenclature

Chemical nomenclature is the term given to the naming of compounds. Chemists use

specific rules and "conventions" to name different compounds. This section is

designed to help you review some of those rules and conventions.

Oxidation and Reduction - Chemical Reaction EquationForming Ionic Compounds - Equalizes Reaction Coefficient

Arrangement of Atoms

Naming Ionic Compounds

Naming Binary Molecular Compounds

Naming Inorganic Acids

Naming Compounds


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Oxidation and Reduction

When forming compounds, it is important to know something about the way atoms willreact with each other. One of the most important manners in which atoms and/or

molecules react with each other is the oxidation/reduction reaction.

Oxidation/Reduction reactions are the processes of losing and gaining electrons

respectively. Just remember, "LEO the lion

says GER:" Lose Electrons Oxidation, Gain Electrons Reduction. Oxidation numbers are

assigned to atoms and compounds as a way to tell scientists where the electrons are ina reaction. It is often referred to as the "charge" on the atom or compound. The

oxidation number is assigned according to a standard set of rules. They are as

follows:An atom of a pure element has an oxidation number of zero.

For single atoms in an ion, their oxidation number is equal to their charge.

Fluorine is always -1 in compounds.

Cl, Br, and I are always -1 in compounds except when they are combined with O or F.

H is normally +1 and O is normally -2.

The oxidation number of a compound is equal to the sum of the oxidation numbers for

each atom in the compound.

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Forming Ionic Compounds

Knowing the oxidation number of a compound is very important when discussing ionic

compounds. Ionic compounds are combinations of positive and negative ions. They aregenerally formed when nonmetals and metals bond. To determine which substance is

formed, we must use the charges of the ions involved. To make a neutral molecule, the

positive charge of the cation (positively-charged ion) must equal the negative charge of the

anion (negatively-charged ion). In order to create a neutral charged molecule, you must

combine the atoms in certain proportions. Scientists use subscripts to identify how many of

each atom makes up the molecule. For example, when combining magnesium and nitrogenwe know that the magnesium ion has a "+2" charge and the nitrogen ion has a "-3" charge.

To cancel these charges, we must have three magnesium atoms for every two nitrogen

atoms:

3Mg2+ + 2N3- --> Mg3N2

Knowledge of the charges of ions is crucial to knowing the formulas of the compoundsformed.

alkalis (1st column elements) form "+1" ions such as Na+ and Li+

alkaline earth metals (2nd column elements) form "2+" ions such as Mg2+ and Ba2+

halogens (7th column elements) form "-1" ions such as Cl- and I-

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Naming Ionic Compounds

The outline below provides the rules for naming ionic compounds:

Positive Ions

1. Monatomic cations (a single atom with a positive charge) take the name of the

element plus the word "ion"

Examples:

Na+ = sodium ion

Zn+2 = zinc ion

2. If an element can form more than one (1) positive ion, the charge is indicated by the

Roman numeral in parentheses followed by the word "ion"

Examples:

Fe2+ = iron(II) ion

Fe3+ = iron (III) ion

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Negative Ions

1. Monatomic anions (a single atom with a negative charge) change their ending to "-ide"

Examples:

O2- = oxide ion

Cl- = chloride ion

2. Oxoanions (negatively charged polyatomic ions which contain O) end in "-ate".

3. Polyatomic anions (a negatively charged ion containing more than one type of element)

often add a hydrogen atom; in this case, the anion's name either adds "hydrogen-" or "bi-" to

the beginning

Example:

CO

3

2-

becomes HCO

3

-

"Carbonate" becomes either "Hydrogen Carbonate" or "Bicarbonate"


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4. When combining cations and anions into an ionic compound, you

always put the cation name first and then the anion name (the

molecular formulas are also written in this order as well.)

Examples:

Na+ + Cl- --> NaCl

sodium + chloride --> sodium chloride

Cu2+ + SO42- -->CuSO4copper(II) + sulfate --> copper(II) sulfate

Al3+ + 3NO3- --> Al(NO3)3

aluminum + nitrate --> aluminum nitrate


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Arrangement of Atoms

In naming ions, it is important to consider "isomers." Isomers are compounds with thesame molecular formula, but different arrangements of atoms. Thus, it is important to

include some signal within the name of the ion that identifies which arrangement you

are talking about. There are three main types of classification, geometric, optical and

structural isomers.

1. Geometric isomers refers to which side of the ion atoms lie. The prefixes used todistinguish geometric isomers are cis meaning substituents lie on the same side of

the ion and trans meaning they lie on opposite sides. Below is a diagram to help you

remember.

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2. Optical isomers differ in the arrangement of four groups around a chiral carbon.

These two isomers are differentiated as L and D.

3. Structural isomers differentiate between the placement of two chlorine atoms

around a hexagonal carbon ring. These three isomers are identified as o, m, and p.Once

again we have given you a few clues to help your memory.


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Naming Binary Molecular Compounds

Molecular compounds are formed from the covalent bonding between non-metallicelements. The nomenclature for these compounds is described in the following set

of rules.

1. The more positive atom is written first (the atom which is the furthest to the left

and to the bottom of the periodic table)

2. The more negative second atom has an "-ide" ending.

3. Each prefix indicates the number of each atom present in the compound.

Number of Atoms Prefix Number of Atoms Prefix

1 Mono 6 Hexa

2 Di 7 Hepta

3 Tri 8 Octa

4 Tetra 9 Nona

5 Penta 10 Deca

Examples:

CO2 = carbon dioxide

P4S10 = tetraphosphorus decasulfide

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Naming Inorganic Acids

1. Binary acids (H plus a nonmetal element) are acids that dissociate into hydrogen

atoms and anions in water. Acids that only release one hydrogen atom are knownasmonoprotic. Those acids that release more than one hydrogen atom are

called polyproticacids. When naming these binary acids, you merely add "hydro-"

(denoting the presence of a hydrogen atom) to the beginning and "-ic acid" to the

end of the anion name.

Examples:

HCl = hydrochloric acidHBr = hydrobromic acid

2. Ternary acids (also called oxoacids, are formed by hydrogen plus another

element plus oxygen) are based on the name of the anion. In this case, the -

ate, and -itesuffixes for the anion are replaced with -ic and -ous respectively. The

new anion name is then followed by the word "acid." The chart below depicts thechanges in nomenclature.

Anion Name Acid Name

Hypo__ite Hypo__ous acid

__ite __ous acid

__ate __ic acid

Per__ate Per__ic acid

Example:

ClO4

- to HClO4

=> perchlorate to

perchloric acid

ClO- to HClO => hypochlorite to

hypochlorous acid

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Chemical Reaction Equation

Equalizes Reaction Coefficient

NN22 (g)(g) + H+ H22 (g)(g) NH NH33(g)(g)Directly:

NN22 (g)(g) + 3H+ 3H22 (g)(g) 2NH 2NH33 (g)(g)

-- AlAl (s)(s) + O+ O22 (g)(g) Al Al22OO33 (s)(s)

Suppose a, b, c, ... ...

aAlaAl (s)(s) + bO+ bO22 (g)(g) cAl cAl22OO33 (s)(s)

Al :Al : a = 2ca = 2cO :O : 2b = 3c2b = 3c

MisalMisal c = 1,c = 1, makamaka ::

aa = 2c = 2.1 = 2= 2c = 2.1 = 2

2b = 3c = 3.12b = 3c = 3.1

b = 3/2b = 3/2

DidapatkanDidapatkan ::

a = 2a = 2 aa

= 4= 4b = 3/2b = 3/2 x2x2 bb

= 3= 3

c = 1c = 1 cc= 2= 2jadijadi ::

4Al4Al (s)(s) + 3O+ 3O22 (g)(g) 2Al 2Al22OO33 (s)(s)

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Equalizes Reaction Coefficient

Cu(s) + HNO3(aq) Cu(NO3)2(aq) + NO2(g) + H2O(l)

With the help of oxidation-reduction:

Cu(s) + HNO3(aq) Cu(NO3)2(aq) + NO2(g) + H2O(l)00 ++55 +2+2 +

4+4

+2+2 --11

x2x2CuCu(s)(s) + HNO+ HNO3(3(aqaq)) Cu(NO Cu(NO33))2(2(aqaq)) + 2NO+ 2NO2(g)2(g) + H+ H22OO(l)(l)

So , ...So , ...

CuCu(s)(s) +4

HNO

+4

HNO

3(3(aqaq)) Cu(NO

Cu(NO

33))2(2(aqaq)) + 2NO

+ 2NO

2(g)2(g) + 2H+ 2H22OO

(l)(l)

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THE END

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