NAMING FORMULAS

1

CHEMICAL EQUATIONS AND MOLES

Unit 5

NAMING

FORMULAS

NOMENCLATURE: NAMING COMPOUNDS

Determine if the compound is:

1. Ionic

2. Covalent

3. Acid

NAMING COMPOUNDS

Types of Compounds

Ionic

Metal and a negative ion

(polyatomic ions)

Covalent Binary Compound of 2

nonmetals

Acids

H___(aq)

Like ionic where H acts like the metal

IDENTIFYING COMPOUNDS

Ionic Compounds

have ionic bonds

contain a metal and a nonmetal

may contain polyatomic ions Table E

Covalent Compounds

have covalent bonds

between 2 or more nonmetals

NO ions

Acids

Start with an H

Table K

THINK ABOUT SOME OF THE NAMES YOU ALREADY KNOW:

Sodium chloride, NaCl

Carbon dioxide, CO2

Sulfuric acid, H2SO4

Carbon monoxide, CO

Copper II sulfate, CuSO4

Carbonic acid, H2CO3

Calcium carbonate, CaCO3

Hydrochloric acid, HCl

Diphosphorous pentoxide, P2O5

2

IDENTIFY THE FOLLOWING AS AN IONIC

COMPOUND, COVALENT COMPOUND OR AN ACID:

HNO3

K2SO4

Li2O

NO

Mg(SCN)2

NH4OH

NaHCO3

SO2

CH3COOH

Ca(OH)2

H3PO4

NaOH

PbSO3

PbSO4

H2SO4

Pb(SO4)2

COMMON NAMES

A lot of chemicals have common names as well

as the proper IUPAC name.

Chemicals that should always be named by

common name and never named by the IUPAC

method are:

H2O water, not dihydrogen monoxide

NH3 ammonia, not nitrogen trihydride

CATION +

ANION --->

COMPOUND

A neutral compound

requires

equal number of +

and - charges.

COMPOUNDS FORMED FROM IONS

Na+ + Cl- --> NaCl

Predicting Charges on Monatomic Ions KNOW THESE !!!!

+1 +2 -3 -2 -1 0

Cd+2

IONIC COMPOUNDS

NH4+

Cl-

ammonium chloride, NH4Cl

NO3-

nitrate ion

NO2-

nitrite ion

POLYATOMIC IONS

3

NAMING MOLECULAR COMPOUNDS

CH4 methane BCl3

boron trichloride

CO2 Carbon dioxide

All are formed

from two or

more

nonmetals.

Ionic

compounds

generally

involve a metal

and nonmetal

(NaCl)

MOLECULAR (COVALENT) NOMENCLATURE

FOR TWO NONMETALS

Prefix System (binary compounds)

1. Less electronegative atom comes first.

2. Add prefixes to indicate # of atoms. Omit mono- prefix on the FIRST element. Mono- is OPTIONAL on the SECOND element (in this class, it’s NOT optional!).

3. Change the ending of the second element to -ide.

PREFIX

mono-

di-

tri-

tetra-

penta-

hexa-

hepta-

octa-

nona-

deca-

NUMBER

1

2

3

4

5

6

7

8

9

10

MOLECULAR NOMENCLATURE PREFIXES

• CCl4

• N2O

• SF6

• carbon tetrachloride

• dinitrogen monoxide

• sulfur hexafluoride

MOLECULAR NOMENCLATURE:

EXAMPLES MIXED PRACTICE

1. Dinitrogen monoxide

2. Potassium sulfide

3. Copper (II) nitrate

4. Dichlorine heptoxide

5. Chromium (III) sulfate

6. Iron (III) sulfite

7. Calcium oxide

8. Barium carbonate

9. Iodine monochloride

4

MIXED PRACTICE

1. BaI2

2. P4S3

3. Ca(OH)2

4. FeCO3

5. Na2Cr2O7

6. I2O5

7. Cu(ClO4)2

8. CS2

9. B2Cl4

ACID NOMENCLATURE

Acids

Compounds that form H+ in water.

Formulas usually begin with ‘H’.

In order to be an acid instead of a gas, binary acids must be

aqueous (dissolved in water)

Ternary acids are ALL aqueous

Examples:

HCl (aq) – hydrochloric acid

HNO3 – nitric acid

H2SO4 – sulfuric acid

NAME THE FOLLOWING ACIDS

HI (aq)

HCl

H2SO3

HNO3

WRITE THE FORMULA!

Hydrobromic acid

Nitrous acid

Carbonic acid

Phosphoric acid

5

CHEMICAL

EQUATIONS

OBJECTIVES

Recognize evidence of chemical change.

Represent chemical reactions with equations.

Classify chemical reactions.

Describe aqueous solutions.

Write complete ionic equations for chemical

reactions in aqueous solutions.

Predict whether reactions in aqueous solutions

will produce a precipitate, water, or a gas.

KEY WORDS CHEMICAL EQUATIONS

A chemical equation is written as an

expression similar to a mathematic

equation that can be compared to a

recipe that a chemist follows in order to

produce desired results.

CHEMICAL EQUATIONS

All chemical equations have reactants and products.

We express a chemical equation as follows:

Reactants Products

The arrow is equivalent to an “=“ math. When we describe the equation we use the word “yields” or “produces” instead of equals

ANATOMY OF A CHEMICAL EQUATION

Products appear on the right

side of the equation.

CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)

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The states of the reactants and products are written in parentheses to the right of each compound.

CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)


Coefficients are inserted to

balance the equation.

CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)

SUBSCRIPTS AND COEFFICIENTS GIVE DIFFERENT

INFORMATION

Subscripts tell the number of atoms of

each element in a molecule

THE STATE OF MATTER SYMBOLS

These 4 symbols represent the state in which

the element or compound is currently in.

1. Solid: (s)

2. Liquid: (l)

3. Gas: (g)

4. Aqueous: (aq): dissolved in water. Ex. Salt in

Water.

EQUATION TYPES

Two Types of Chemical Equations:

1. Word Equations: use words to describe the

elements or compounds present.

Iron (s) + Chlorine (g) Iron (III) Chloride (s)

2. Skeleton Equations: use symbols for the

elements or compounds present.

Much less cumbersome.

Fe (s) + Cl2 (g) FeCl3 (s)

EVIDENCE OF CHEMICAL REACTIONS

First, we need a definition: Chemical Reaction:

the process by which the atoms of one or more

substances are rearranged to form different

substances.

What evidence suggests to you that a chemical

reaction has taken place?

Color change, fizz, burst, burn, temperature

change, odor, sudden appearance of a solid in a

liquid.

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REACTION

TYPES

IDENTIFYING REACTION TYPES

Reactions are classified by their products.

5 basic types of chemical reactions are:

synthesis or combination reactions

decomposition reactions

single replacement reactions

double replacement reactions

combustion reactions

SYNTHESIS (COMBINATION) REACTIONS

Examples:

N2 (g) + 3 H2 (g) 2 NH3 (g)

C3H6 (g) + Br2 (l) C3H6Br2 (l)

2 Mg (s) + O2 (g) 2 MgO (s)

Two or more

substances

react to form

one product

DECOMPOSITION REACTIONS

Examples:

CaCO3 (s) CaO (s) + CO2 (g)

2 KClO3 (s) 2 KCl (s) + O2 (g)

2 NaN3 (s) 2 Na (s) + 3 N2 (g)

One substance breaks

down into two or more

substances

SINGLE REPLACEMENT REACTIONS

Single replacement reactions occur when one

chemical takes the place of another in a

reaction.

In the typical single replacement reaction, an

element trades places with one of the ions in a

compound.

SINGLE REPLACEMENT REACTIONS

A + CD AD + C

Note: Element A replaces ion C in the reaction.

The clue in this reaction is:

Element+Compound Element + Compound

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TYPE: SINGLE DISPLACEMENT

Example: Zn + CuCl2

Zn Cl Cl Cu +

General: AB + C AC + B

Cl Cl Zn Cu +

See Reference Tables

THE ACTIVITY SERIES

THE ACTIVITY SERIES

We have looked at several reactions: Fe + CuSO4 Cu + Fe2(SO4)3 Li + H2O LiOH + H2 Such experiments reveal trends. The activity series ranks the relative reactivity of metals. It allows us to predict if certain chemicals will undergo single displacement reactions when mixed: metals near the top are most reactive and will displacing metals near the bottom.

Fe + CuSO4

Ni + NaCl

Li + ZnCO3

Al + CuCl2

Cu + Fe2(SO4)3

NR (no reaction)

Zn + Li2CO3

Cu + AlCl3

Q: Which of these will react?

H is the only nonmetal listed. H2 may be displaced from acids or can be given off when a metal reacts with H2O (producing H2 + metal hydroxide). The reaction with H2O depends on metal reactivity & water temp.

A: No for cold, yes if it is hot/steam

Mg + H2O

H2 + ZnCl2

H2 + Mg(OH)2

Q: Zn + HCl

Q: will Mg react with H2O?

DOUBLE REPLACEMENT REACTIONS

Double replacement reactions are

identified by two ions trading places and

forming new compounds.

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DOUBLE REPLACEMENT REACTIONS

AB + CD AD + CB

Note: Notice that one ion from compound AB

replaces one ion from compound CD.

Clue:

Compound+CompoundCompound+Compound

DOUBLE REPLACEMENT REACTIONS OCCUR

ONLY IF:

water is a product

A gas is produced (HCl)

A precipitate is produced

You must predict the product or there is no

reaction!

TYPE: DOUBLE REPLACEMENT

Example: MgO + CaS

General: AB + CD AD + CB

S O

Mg Ca +

O S

Mg Ca +

COMBUSTION REACTIONS

Examples:

CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (g)

C3H8 (g) + 5 O2 (g) 3 CO2 (g) + 4 H2O (g)

Rapid reactions that

produce a flame

Most often involve

hydrocarbons

reacting with oxygen

in the air

COMBUSTION REACTIONS

Combustion reactions are the ones that burn (or explode!). There are two types of combustion reactions—complete or incomplete reactions.

These reactions are identified by their products. They either produce carbon monoxide and water or carbon dioxide and water.

COMPLETE COMBUSTION REACTIONS

These reactions burn “efficiently” which

means they produce carbon dioxide and

water. These reactions typically burn

cleanly and leave very little residue

behind.

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COMPLETE COMBUSTION REACTIONS

CH4 + O2 CO2 + H2O

They may also be written:

CH4 CO2 + H2O

(O2 is usually written above the arrow.)

Clue: CO2 (carbon dioxide) in the product

along with water

CONSERVATION OF MATTER

The law of conservation of matter tells

us that matter can neither be created

nor destroyed. It is transformed from

one form to another.

We follow the conservation of matter law

when we balance equations.

BALANCING A CHEMICAL EQUATION

A chemical equation is balanced when the

ions or atoms found on the reactant side

of the equation equals that found on the

product side.

The arrow can be considered the balance

point.

COEFFICIENTS

We use coefficients in front of elements or

compounds on either side of the

reaction to balance the equation. (The

coefficients go in front of the chemical!)

We cannot change subscripts because it

would create new materials that are not

part of reaction process.

The equation is balanced only by adjusting the coefficients of the

formulas as necessary to get whole number coefficients.

NEVER introduce extraneous formulas

NEVER change subscripts of the formulas

Balancing Equations

Why?-----Atoms are conserved in chemical reactions

A chemical equation is made up of reactants on the left

And the products on the right. An arrow signifies reactants

going to products

BALANCING EQUATIONS: MGO

The law of conservation of mass states that

matter can neither be created or destroyed

Thus, the number of a particular atom is the

same on both sides of a chemical equation

Example: Magnesium + Oxygen

Mg + O2 MgO

However, this is not balanced

O Mg O + Mg O

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BALANCE EQUATIONS BY “INSPECTION”

From Mg + O2 MgO

2Mg + O2 2MgO is correct

Mg + ½O2 MgO is incorrect

Mg2 + O2 2MgO is incorrect

4Mg + 2 O2 4MgO is incorrect

BALANCE THIS EQUATION!

Na + Cl2 NaCl

Na- 1 Na-1

Cl- 2 Cl-1

**note that the number of sodiums balance but the chlorine does not. We will have to use coefficients in order to balance this equation.

INSERTING SUBSCRIPTS

Na + Cl2 2 NaCl

Na- 1 Na-1 2

Cl- 2 Cl-1 2

** Now the chlorine balances but the

sodium does not! So we go back and

balance the sodium.

FINALLY BALANCED!

2Na + Cl2 2 NaCl

Na- 1 2 Na-1 2

Cl- 2 Cl-1 2

**Since the number of each element on the reactant side and the product side of the equation are equal, the equation is balanced.

BALANCING EQUATION PRACTICE

Hints: start with elements that occur in

one compound on each side. Treat

polyatomic ions that repeat as if they

were a single entity.

Balancing Chemical Equations

1. Write the correct formula(s) for the reactants on

the left side and the correct formula(s) for the

product(s) on the right side of the equation.

Ethane reacts with oxygen to form carbon dioxide and water

C2H6 + O2 CO2 + H2O

2. Change the numbers in front of the formulas

(coefficients) to make the number of atoms of

each element the same on both sides of the

equation. Do not change the subscripts.

3.7

2C2H6 NOT C4H12

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BALANCING EQUATION PRACTICE

a) P4 + O2 P4O10

b) Li + H2O H2 + LiOH

c) Bi(NO3)3 + K2S Bi2S3 + KNO3

d) C2H6 + O2 CO2 + H2O

C2H6 + O2 CO2 + H2O

FORMULA

WEIGHTS

FORMULA WEIGHT (FW)

Sum of the atomic weights for the atoms in a chemical formula

So, the formula weight of calcium chloride, CaCl2, would be

Ca: 1(40.1 amu)

+ Cl: 2(35.5 amu)

111.1 amu

These are generally reported for ionic compounds

MOLECULAR WEIGHT (MW)

Sum of the atomic weights of the atoms in

a molecule

For the molecule ethane, C2H6, the

molecular weight would be

C: 2(12.0 amu) + H: 6(1.0 amu)

30.0 amu

PERCENT COMPOSITION

One can find the percentage of the mass of

a compound that comes from each of the

elements in the compound by using this

equation:

% element = (number of atoms)(atomic weight)

(FW of the compound) x 100

PERCENT COMPOSITION

So the percentage of carbon in ethane is…

%C = (2)(12.0 amu)

(30.0 amu)

24.0 amu

30.0 amu = x 100

= 80.0%

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MOLES

MOLES

74

Moles Mass of

Element

Mass of

Compound

Atoms of

Element

Molecules of

Compound

Volume of

gas (STP)

/ atomic mass =

= atomic mass x

= 6.02 x 1023 /

X 6.02 x 1023 =

/ 22.4

L =

= 2

2.4

L x

AVOGADRO’S NUMBER

6.02 x 1023

1 mole of 12C has a

mass of 12 g

MOLAR MASS

By definition, these are the mass of 1 mol of a

substance (i.e., g/mol)

The molar mass of an element is the mass number

for the element that we find on the periodic table

The formula weight (in amu’s) will be the same

number as the molar mass (in g/mol)

1 mole of a gas occupies 22.4 liters in volume.

USING MOLES

Moles provide a bridge from the molecular scale to

the real-world scale

MOLE RELATIONSHIPS

One mole of atoms, ions, or molecules contains

Avogadro’s number of those particles

One mole of molecules or formula units contains

Avogadro’s number times the number of atoms or

ions of each element in the compound

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FINDING

EMPIRICAL

FORMULAS

IDENTIFYING EMPIRICAL FORMULAS

Empirical formulas are the reduced formula.

Ex. Molecular formula C6H12

Empirical formula is CH2

ELEMENTAL ANALYSES

Compounds

containing other

elements are

analyzed using

methods analogous

to those used for C, H

and O

STOICHIOMETRIC CALCULATIONS

The coefficients in the balanced equation give the

ratio of moles of reactants and products

STOICHIOMETRIC CALCULATIONS

From the mass of

Substance A you can

use the ratio of the

coefficients of A and B

to calculate the mass

of Substance B formed

(if it’s a product) or

used (if it’s a reactant)

NAMING FORMULAS

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