Download CB I Chemical Bonding

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CB I
Chemical Bonding
CHEM101/3, J1
8-2
2007 10 01
Nomenclature & Stoichiometry
HT
Suitable Textbook Problems
General Advice
In each section, try the more difficult problems first.
If you have difficulties try the simpler ones also, until you are fully proficient with the topic
Nomenclature
• General
3: 55 - 59 odds
• Nomenclature Review
Mole Concept
• Stoichiometry Review
3: 5 - 13 odds
Balancing Chemical Equations
Ref
Prob
10: 1 - 2
1: 5 - 7
3: 1 - 3, 6
4: 1 - 5
4: 1 - 9 odds
Percent Composition
3: 15 - 21, 25 -33
• see list next page
• HMWK #4 and #5
Stoichiometry
4: 13 - 21, 27 - 31, 37, 39, 43, 45, 55, 57, 63, 65
Adv Rdg 10: 3 - 4
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General
At STP (standard temp. & pressure),
few elements exist as single atoms:
N. G., (noble gases) only
The rest of the elements have bonds:
metals: metallic bond
non-metals: covalent bond
In compounds, 2 kinds of bonds exist
ionic
transfer of e–’s
covalent
Ionic Bonding
metal
loses e–’s
cation
non-metal
gains e–’s
anion
Ions held together (bound) by
electrostatic (“Coulombic”) forces.
Notes:
In solids, 3- D lattice (grid, network) exists
(no “one - on - one” relationship !)
see Pet. Fig. 12.38
sharing of e–’s
Driving force:
to get “octet” of e–’s
= “full shells”
=“max Zeff” on each atom
ion pairs, Na+ Cl– , may exist in
gas state or liquid (molten) phase
generally, in aqueous solution
cations and anions are separated by H2O
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Pet. Fig. 12.38 3 - D Lattice of Ionic Solids
Covalent Bonding
•
e–’s shared to get “octet”
for every atom
•
lowest energy at
“certain distance” = bond length
•
this energy = bonding energy,
= energy required to separate
bonded atoms completely
•
Ex. Covalent bonding in H2 molecule
see Pet. Fig. 11.1
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Pet. Fig. 3.4 Covalent Bonding in S and P
Pet. Fig. 11.1 Covalent Bonding in H2
S8
P4
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1. Know symbol ↔ name & find position in P.T. quickly for
Cs Ba
HF (aq) __________________
HI (aq) ____________________
5. Binary Ionic Cmpds
first 36 elements plus
Sr
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4. Binary acids in H2O: hydro …ic acid
Nomenclature
Pd Ag Cd
Sn Sb
Pt
Pb Bi
Au Hg
A. main group elements
I Xe
U
2. Diatomic/ Multiatomic Elements in their “standard states”:
•
cation, anion (…ide)
•
determine charge on ions (group in P.T.)
•
smallest whole number ratio, balance for electroneutrality
= “crossover method”
“ Cl i f Br o h n “ → Cl2, I2, F2, Br2, O2, H2, N2
also S8 , P4
3. Binary Covalent Cmpds ( “nonmetal + nonmetal”)
•
less electronegative element first
•
more electronegative element second (ending …ide)
•
use Latin/Greek prefixes ((mono), di, tri, tetra, penta, hexa, hepta, octa,
CaO _____________________
beryllium fluoride ____________
SrI2 _____________________
magnesium nitride ____________
K2S _____________________
barium sulfide ____________
B. transition metals, also Sn, Pb
nona, deca)
CO ____________________
SF6 ____________________
P4O10 ____________________
Indicate charge on cation w/ Roman numeral
TiCl4 _____________________
chromium(II) chloride ___________
NiS _____________________
copper(I) oxide ____________
Fe2S3 _____________________
iron(III) sulfide ____________
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8. Acidic Anions
6. Standard Oxoacids & Derived Anions
H2CO3 carbonic acid
CO32– carbonate
HNO3 nitric acid
NO3–
______________
HSO4– _____________________ sodium hydrogen sulfate _________
H3PO4 phosphoric acid
PO43–
______________
NaHSO3 ____________________ dihydrogen phosphate anion ______
H2SO4 sulfuric acid
SO42–
______________
K2HPO3 ____________________ sodium hydrogen carbonate _______
HClO3 chloric acid
ClO3–
______________
HBrO3 bromic acid
BrO3– _______________
HIO3
IO3–
(incomplete loss of H from acid): hydrogen ….ate, ite, …
9. Hydrates: indicate # of H2O by Greek/Latin letters
CuSO4 • 5H2O copper(II) sulfate pentahydrate
iodic acid
_______________
Na2SO4• 10H2O _______________________________________
10. Special Cases
7. More or Less O than “standard” acid/anion
2 less O : hypo…..ous acid;
1 less O :
…..ous acid;
1 more O: per…..ic acid;
hypo…..ite
…..ite
per…..ate
HClO2 _____________________ potassium perchlorate ___________
HIO4 _____________________
sodium nitrite ____________
HNO2 _____________________ sodium sulfite ____________
KBrO _____________________ ammonium phosphite ___________
NH3 ammonia
OH –
NH4+ ammonium
CN –
H2O water
C2H3O2– acetate
cyanide
MnO4
H2O2 hydrogen peroxide
HC2H3O2 (= CH3CO2H)
hydroxide
acetic acid
–
2–
CrO4
permanganate
chromate
Cr2O72– dichromate
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4. Binary acids in H2O: hydro …ic acid
Nomenclature w/ Answers
HF (aq) hydrofluoric acid
1. Know symbol ↔ name & find position in P.T. quickly for
HI (aq) hydroiodic acid
5. Binary Ionic Cmpds
first 36 elements plus
A. main group elements
Sr
Cs Ba
Pd Ag Cd
Sn Sb
Pt
Pb Bi
Au Hg
I Xe
U
•
cation, anion (…ide)
•
determine charge on ions (group in P.T.)
•
smallest whole number ratio, balance for electroneutrality
= “crossover method”
2. Diatomic/ Multiatomic Elements in their “standard states”:
“ Cl i f Br o h n “ → Cl2, I2, F2, Br2, O2, H2, N2
also S8 , P4
CaO calcium oxide
beryllium fluoride BeF2
SrI2 strontium iodide
magnesium nitride Mg3N2
K2S potassium sulfide
barium sulfide BaS
3. Binary Covalent Cmpds ( “nonmetal + nonmetal”)
•
less electronegative element first
•
more electronegative element second (ending …ide)
•
use Latin/Greek prefixes ((mono), di, tri, tetra, penta, hexa, hepta, octa,
B. transition metals, also Sn, Pb
Indicate charge on cation w/ Roman numeral
nona, deca)
TiCl4 titanium(IV) chloride
chromium(II) chloride CrCl2
NiS nickel(II) sulfide
copper(I) oxide Cu2O
Fe2S3 iron(III) sulfide
iron(III) sulfide Fe2S3
CO carbon monoxide
SF6 sulfur hexafluoride
P4O10 tetraphosphorus decaoxide
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8. Acidic Anions
6. Standard Oxoacids & Derived Anions
(incomplete loss of H from acid): hydrogen ….ate, ite, …
HSO4– hydrogen sulfate
sodium hydrogen sulfate NaHSO4
H2CO3 carbonic acid
CO32– carbonate
HNO3 nitric acid
NO3–
nitrate
NaHSO3 sodium hydrogen sulfite dihydrogen phosphate anion H2PO4 –
H3PO4 phosphoric acid
PO43–
phosphate
K2HPO3 potassium hydrogen phosphite
H2SO4 sulfuric acid
SO42–
sulfate
HClO3 chloric acid
ClO3–
chlorate
HBrO3 bromic acid
BrO3– bromate
HIO3
IO3–
sodium hydrogen carbonate NaHCO3
9. Hydrates: indicate # of H2O by Greek/Latin letters
CuSO4 • 5H2O copper(II) sulfate pentahydrate
Na2SO4• 10H2O sodium sulfate decahydrate
10. Special Cases
iodic acid
iodate
7. More or Less O than “standard” acid/anion
2 less O : hypo…..ous acid;
1 less O :
…..ous acid;
1 more O: per…..ic acid;
hypo…..ite
…..ite
per…..ate
HClO2 chlorous acid
potassium perchlorate KClO4
HIO4 perchloric acid
sodium nitrite NaNO2
HNO2 nitrous acid
sodium sulfite Na2SO3
KBrO potassium hypobromite
ammonium phosphite (NH4)3PO3
OH –
NH3 ammonia
+
NH4
ammonium
CN
H2O2 hydrogen peroxide
C2H3O2– acetate
cyanide
MnO4 –
H2O water
HC2H3O2 (= CH3CO2H)
hydroxide
–
acetic acid
2–
CrO4
permanganate
chromate
Cr2O72– dichromate
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Derivation of Avogadro’s Number, NA
Chem. Formulas
Ex. hydrogen peroxide
• empirical
The following are definitions:
(arbitrary, but optimal selection)
• (relative) atomic mass of C-12 = 12 u (exact)
(HO)
smallest whole number
ratio of atoms
• 1 mol of C-12 = 12 g C-12 (exact)
• molar mass (MM) of C-12 = 12 g/mol
• molecular
gives the number
To find the number of atoms per mol (NA),
H2O2
of each atom in molecule
we need to determine the absolute mass (m)
of a C-12 atom;
• structural
(this can be done by mass spectrometry, X-ray crystalography ...)
shows all bonds,
H–O–O–H
m of C-12 (by experiment) = 1.993 x 10–23 g
may include geometric info,
H
∴
O
O
MM
12 g/mol
NA = m = 1.993x10–23g
= 6.022 x 1023 mol–1
H
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Mole Concept
Mass
Moles
1 mol = 6.02 x 1023 “things”
Use MM as CF (conversion factor)
NA = Avogadro’s #; units: mol–1
Practice
can refer to
# of moles in 89.2 g NaF ?
atoms
molecules
formula units
ions
electrons
photons
electronic transitions
molecular conversions
(“dogs” ?)
Molar Mass (MM)
mass of 1 mol of “particles”;
g
units: mol
to determine, see Pet., p. 72
W
G
MM = 42.0 g/mol
1 mol
89.2 g x 42.0 g = 2.12 mol
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balancing ...
Balancing Chem. Equations
Ex.
• # of atoms of each kind same on both sides
__ PCl5 + __ H2O
• total charges same on both sides
• “systematic trial & error method”
P: 1
- start with an element
in most complicated cmpd
__ H3PO4 + __ HCl
1
Cl: (1 x 5)
- balance O, H near end
5
O:
4
(4)
- do elements last
H:
- multiply/ divide to get
simplest whole number coefficients
(4 x 2)
1 PCl5 + 4 H2O
(3 x 1)
(5 x 1)
1 H3PO4 + 5 HCl
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Stoichiometric Calculations
W
G
MM
mass G
moles G
• Check how much Product each Reactant can make
MM
moles W
Limiting Reactant (L.R.)
mass W
• Reactant that makes least Product = L.R.
W
G = M.R. (molar ratio) of W/G
Yield
Ex. In the synthesis of NH3,
how many g of N2 are needed to convert 35.2 g H2?
W
G
N2 + 3 H2 → 2 NH3
1mol H2
1mol N2 28.0g N2
35.2 g H2 x 2.02g H x 3mol N x 1mol N
2
2
2
= 163 g N2
actual:
obtained in experiment ( g or mol)
theoretical: calculated by stoichiometry ( g or mol)
(take into account L.R.)
% yield:
actual
theoretical x 100%
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% Composition from Chem. Formula
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Determination of Empirical Formula
(from “mass data”, or “combustion data”, or ...)
Ex. Percentage of U in “Yellow Cake” ?
convert to mole data for each element,
then find simplest whole number ratio
“yellow cake” = U3O8
Ex. A cmpd contains 74.1% C, 8.64% H, 17.3% N.
Empirical formula ?
Imaginary Reaction:
U3O8 + ... → 3 U + ...
Base on 100g cmpd:
base on 100g compound
mass (g)
divide by
MM
moles
(mol)
divide by
“lowest moles”
nearest whole
numbers
1mol U3O8
3mol U
238g U
100g U3O8 x 842g U O x 1mol U O x 1mol U
3 8
3 8
= 84.8 g U
C 74.1
12.01
6.17
4.99
5
H 8.64
1.008
8.57
6.93
7
This corresponds to 84.8% U in “yellow cake”,
since we based our calculation on 100 g.
N 17.3
14.01
1.24
1.00
1
∴ Empirical Formula: (C5H7N)
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Molecular Formula
Miscellaneous
Need MM data (from experiment)
Density
Divide
usually:
MM of cmpd by
MM of “empirical formula”
solids, liquids : g/mL
gases:
g/L
(can be used as C.F.’s)
to get multiplication factor
Ex. Empirical formula = (CH); MM ≈ 80 g/mol
Molecular Formula?
Concentration
MM of “empirical formula”: 13.0 g/mol
usually: mol/L (“M”)
Divide:
80 g/mol
13 g/mol = 6.15
Dilution
close to 6; multiply emprical formula by 6
a.) c1V1 = c2V2 , or
Molecular formula: (CH) x 6 = C6H6
V1
V3
b.) c1 x V x V x .... = cfinal
2
4
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CB I Summary
• Distinguish between ionic and covalent bonding
• Systematic Nomenclature Review:
distiguish 8 different cases;
convert name↔ formula
• Systematic Stoichiometry Review
mole concept
balancing chem. equations
mass relations in chem. rxns
chem. compostion from formula
empirical formula from composition or
reaction data
molecular formula from molecular mass and
empirical formula