chapter 3 molecular composition. molecules these molecular compounds (molecules) tend to behave as a...

Chapter 3

Molecular Composition

Molecules

These molecular compounds (molecules) tend to behave as a single unit, not as an aggregate like ionic compounds

When nonmetals bond with other nonmetals, they do not bond as ions. Instead, they remain uncharged and share electrons to form covalent bonds.

Ethyl acetate (“non-acetone” nail-polish remover) - a molecular compound

Names of Ions

Naming binary ionic compounds

Named as: Cation + Anion:

NaCl =

MgBr =

Al2O3 =

ZnS =

Transition metal compounds are named similarly, but the charge of the metal is specified:

Fe2O3 =

FeO =

HgS =

VCl3 =

TiO2 =

Naming binary ionic compounds

Named as: Cation + Anion:

NaCl = sodium chloride

MgBr = magnesium bromide

Al2O3 = aluminum oxide

ZnS = zinc sulfide

Transition metal compounds are named similarly, but the charge of the metal is specified:

Fe2O3 =

FeO =

HgS =

VCl3 =

TiO2 =

Naming binary ionic compounds

Named as: Cation + Anion:

NaCl = sodium chloride

MgBr = magnesium bromide

Al2O3 = aluminum oxide

ZnS = zinc sulfide

Transition metal compounds are named similarly, but the charge of the metal is specified:

Fe2O3 = Iron (III) oxide

FeO = Iron (II) oxide

HgS = Mercury (II) sulfide

VCl3 = Vanadium (III) chloride

TiO2 = Titanium (IV) oxide

Ions composed of more than one atom

These are covalently bonded atoms that have charges, and act in aggregate as an ion.

Polyatomic ions

Polyatomic ions

FeSO4 =

Bi(C2H3O2) 3 =

MnCO3 =

Ti(NO3)4 =

Pt(CN)4 =

Naming Polyatomic Ions

FeSO4 = iron (II) sulfate

Bi(C2H3O2) 3 = bismuth (III) acetate

MnCO3 = manganese (II) carbonate

Ti(NO3)4 = titanium (IV) nitrate

Pt(CN)4 = platinum (IV) cyanide

Naming Polyatomic Ions

mono 1 penta 5

di 2 hexa 6

tri 3 hepta 7

tetra 4 octa 8

If a pair of atoms can form more than one mixture, then we use prefixes to describe the number of each atom type:

Binary nonmetalic compounds

Some ionic compounds may have water “associated” with the compound. We describe these compounds as hydrates and name them as such:

CoCl2 cobalt (II) chloride

CoCl2•6H2O

CuSO4 copper (II) sulfate

CuSO4•5H2O

Hydrated Compounds

Some ionic compounds may have water “associated” with the compound. We describe these compounds as hydrates and name them as such:

CoCl2 cobalt (II) chloride

CoCl2•6H2O cobalt (II) chloride hexahydrate

CuSO4 copper (II) sulfate

CuSO4•5H2O copper (II) sulfate pentahydrate

Hydrated Compounds

CoCl2CoCl2•6H2O

(Bronstead) Acids produce H3O+ ions when dissolved in water

There are different rules for naming binary acids to emphasize their acidity

HCl : not hydrogen chloride - hydrochloric acid

HI: not hydrogen iodide - hydroiodic acid

Binary Acids

Series of acids/anions formed by the successive addition of one oxygen atom

XO– hypo___ite ion HXO hypo ___ ous acid

XO2

– ___ite ion HXO2 ___ ous acid

XO3

– ___ate ion HXO3 ___ ic acid

XO4

– per ___ ate ion HXO4 per ___ric acid

Oxoacids/oxoanions

Series of acids/anions formed by the successive addition of one oxygen atom

ClO– hypochlorite ion HClO hypochlorous acid

ClO2

– chlorite ion HClO2 chlorous acid

ClO3

– chlorate ion HClO3 chloric acid

ClO4

– perchlorate ion HClO4 perchloric acid

Oxoacids/oxoanions

Law of Conservation of Mass

Lavoisier (1743-1794): The total mass of all substances present after a chemical reaction (the products) is the same as the total mass of all substances present before the reaction (the reactants)

Stoichiometry includes all the quantitative relationships involving:

atomic and formula masses

chemical formulas

amount (moles) of substances

Stoichiometry

Mass Percent

Table salt is what percent sodium by mass?

Determining Percent Composition From a Chemical Formula

The formula mass (also called molecular mass, formula weight or molecular weight) is the total mass of all the elements that make up the compound

Aspartame

An unknown compound is 26.1% carbon, 4.4% hydrogen and 69.5% oxygen by mass. What is the empirical formula?

1. Choose an arbitrary sample size (100g is a good choice)

2. Convert percent mass moles

3. Write a formula with the molar values as subscripts

4. Divide each subscript by the smallest subscript value

5. Multiply all subscripts by a small whole number to make the subscripts integral (if necessary)

Finding an Empirical Formula From Mass

Percent