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