chem 101 week 4
TRANSCRIPT
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Chem 101Powerpoints
Week ending 2/10/2012End of Chapter 2Chapter 3 Part 1
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Naming Compounds that contain a Metal and a Non-Metal
• There are two types of Binary Ionic Compounds that result from the combination of an anion and a cation
I. Metal present forms only one type of cation
II. Metal present can form two or more cations with different charges
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Type I Binary Ionic Compounds
• The cation is always named first and the anion second
• A simple cation (from a single atom) takes its name from the name of the element
ie. Na+ - sodium• A simple anion (obtained from a single atom) is
named by taking the first part of the element name (root) and adding the suffix –ide
ie. Cl- - chloride
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Examples of Type I Compounds
• NaCl sodium chloride• KI potassium iodide• CaS calcium sulfide• CsBr cesium bromide• AlCl3 aluminum chloride
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Type II Binary Ionic Compounds• Recall that the transition metals can form more than one type
of cation• When a transition metal is present you must specify which
cation is involved in the compound• Newer method uses roman numerals to specify the charge
on the cationie. FeCl2 -iron can form Fe+2 and Fe+3
-it must balance the anions charge -Cl- x 2 = -2 -therefore the cation must be Fe+2
- Iron(II) chloride
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Older Method of Naming Type II Compounds
• The older method uses the endings –ic and –ous to indicate charge on the transition metal in a compound
• -ic – designates the ion with higher charge• -ous- designates the ion with the lower charge ie. Fe+2 -Ferrous and Fe+3 –Ferric FeCl2 – ferrous chloride
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More Type II Names
• Fe2O3
• Fe must cancel the charge of the oxide• O-2(3) = 6• Therefore Iron (III) oxide or ferric oxide
• PbCl4
• Lead must cancel the charge on chloride• Cl-1 (4) = 4• Therefore lead (IV) chloride not lead (II)
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Binary Compounds Containing Only Non-Metals
• Compounds that contain 2 non-metals or a non-metal and metalloid
• Rules for Naming Binary Compounds Containing Only Non-Metals
1. The first element in the formula is named first using the full element name
2. The second element is named as though it were an anion3. Greek prefixes are used to denote the numbers of atoms
present4. The prefix mono is never used for naming the first element
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Greek prefixesNumber Prefixes
1 mono
2 di
3 tri
4 tetra
5 penta
6 hexa
7 hepta
8 octa
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Examples
• CO • Compound of two non-metals • Carbon monoxide not monocarbon monoxide
• BF3 Boron trifluoride
• NO nitrogen monoxide• N2O5 dinitrogen pentoxide
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Compounds that Contain Polyatomic Ions
• Compounds like NH4NO3
• Contain polyatomic ions – charged entities composed of several atoms bound together
-polyatomic ions are given special names that must be memorized in order to name compounds containing them
-most impt. Ones are in table 2.3 on pg. 61 and in handout
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Oxyanions
• Series of polyatomic ions that contain an atom of a given element and a different number of oxygen atoms
• ClO-, ClO2-, ClO3
-, ClO4-
• SO32-, SO4
2-
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Oxyanions
• When there are 2 members: -the one with the smaller number of oxygen
atoms ends with -ite -The one with the larger number of oxygen
atoms ends in –ate• When more than two members: -hypo (less than) is added as a prefix -per (more than) is added as a prefix
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Oxyanions
• SO42- SO3
2-
sulfate sulfite
• NO3- NO2
-
nitrate nitrite
• ClO- ClO2- ClO3
- ClO4-
hypochlorite chlorite chlorate perclorate
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Naming Compounds with Polyatomic Ions
• Similar to naming Binary Ionic compounds• Must learn to recognize the common
polyatomic ions• When the polyatomic ion is combined with a
transition metal, a roman numeral is required to specify cation charge
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Compounds with Polyatomics and Oxoanions
– Na2SO4
sodium sulfate– KNO3
potassium nitrate– Mn(OH)2
manganese (II) hydroxide– Na2SO3 sodium sulfite– NH4Cl ammonium chloride
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Writing Chemical Formulas from Names
• Thus far we have focused on determining a compounds systamatic name from a chemical formula
• Being able to reverse the process is crucial!• Laboratory procedures describe compounds by name
yet reagent jars typically show the formula only• It is essential that you be able to get the formula of a
compound from its name!
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To write chemical formulas from names
• **it is essential to learn the name, composition and charge of the common polyatomic ions
• if you do not recognize these ions by formula and by the name you will not be able to write the compounds name given its formula or the compounds formula given its name
• Must also learn the names of the common acids
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Acids
• When dissolved in water certain molecules produce hydrogen ions H+ (protons)
• Such molecules are called acids• Acids have a sour taste and turn blue litmus
red• Acids can be viewed as a molecule with one or
more H+ ions attached to an anion
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Naming Acids
• An acids name will depend on whether the anion part of the acid contains oxygen
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Rules for Naming Acids
1. If the anion does not contain oxygen the acid is named using the prefix hydro- and the suffix –ic attached to the root name for the anion element followed by the word “acid”
2. When the anion contains oxygen the acid name is formed from the root name of the central element of the anion or the anion name with a suffix of –ic or –ous
–When the anion ends in –ate the suffix -ic or -ric is used –When the anion ends in –ite the suffix –ous is used
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Naming Acids
HCl (g) hydrogen chlorideHCl(aq) hydrochloric acidHCN(aq) hydrocyanic acidH2S(aq) hydrosulfuric acidH2SO4(aq) sulfuric acid (sulfate)
H3PO4(aq) phosphoric acid (phosphate)
HC2H3O2(aq) acetic acid (acetate)HNO3(aq) nitric acid (nitrate)H2SO3(aq) sulfurous acid (sulfite)HNO2 (aq) nitrous acid (nitrite)
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Oxyacids
• Acids formed from oxyanions• To name oxyacids we use Rule #2 -ate → -ic or –ric -ite → -ous
Acid Anion Name HClO4 perchlorate Perchloric acid
HClO3 chlorate Chloric acid
HClO2 chlorite Chlorous acid
HClO Hypochlorite Hypochlorous acid
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Final Note
• Thus far we have focused on determining a compounds systamatic name from its chemical formula
• REVERSING THE PROCESS IS CRUCIAL! –laboratory procedures describe compounds by
name, yet reagent jars typically show the formula only
–it is essential that you be able to write the formula of a compound from its name
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A base can be defined as a substance that yields hydroxide ions (OH-) when dissolved in water.
NaOH sodium hydroxide
KOH potassium hydroxide
Ba(OH)2 barium hydroxide
2.7
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Hydrates are compounds that have a specific number of water molecules attached to them.
BaCl2•2H2O
2.7
LiCl•H2O
MgSO4•7H2O
Sr(NO3)2 •4H2O
barium chloride dihydrate
lithium chloride monohydrate
magnesium sulfate heptahydrate
strontium nitrate tetrahydrate
CuSO4•5H2O CuSO4
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2.7
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Organic chemistry is the branch of chemistry that deals with carbon compounds
C
H
H
H OH C
H
H
H NH2 C
H
H
H C OH
O
methanol methylamine acetic acid
2.7
Functional Groups
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Chapter 3
Part 1
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Mass Relationships in Chemical Reactions
Chapter 3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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By definition: 1 atom 12C “weighs” 12 amu
On this scale
1H = 1.008 amu
16O = 16.00 amu
Atomic mass is the mass of an atom in atomic mass units (amu)
Micro Worldatoms & molecules
Macro Worldgrams
3.1
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Natural lithium is:
7.42% 6Li (6.015 amu)
92.58% 7Li (7.016 amu)
7.42 x 6.015 + 92.58 x 7.016100
= 6.941 amu
3.1
Average atomic mass of lithium:
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Average atomic mass (6.941)
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© 2009, Prentice-Hall, Inc.
Formula Weight (FW)• A formula weight is the 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
• Formula weights are generally reported for ionic compounds.
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Formula mass (formula weight) is the sum of the atomic masses (in amu) in a formula unit of an ionic compound.
1Na 22.99 amu1Cl + 35.45 amuNaCl 58.44 amu
For any ionic compound
formula mass (amu) = molar mass (grams)
1 formula unit NaCl = 58.44 amu1 mole NaCl = 58.44 g NaCl
3.3
NaCl
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Do You Understand Formula Mass?
What is the formula mass of Ca3(PO4)2 ?
3.3
1 formula unit of Ca3(PO4)2
3 Ca 3 x 40.08
2 P 2 x 30.978 O + 8 x 16.00
310.18 amu
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© 2009, Prentice-Hall, Inc.
Molecular Weight (MW)
• A molecular weight is the 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)
30.0 amu+ H: 6(1.0 amu)
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Molecular mass (or molecular weight) is the sum ofthe atomic masses (in amu) in a molecule.
SO2
1S 32.07 amu2O + 2 x 16.00 amu SO2 64.07 amu
For any molecule
molecular mass (amu) = molar mass (grams)
1 molecule SO2 = 64.07 amu
1 mole SO2 = 64.07 g SO2 3.3
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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
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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
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Avogadro’s Number
• 6.02 x 1023
• 1 mole of 12C has a mass of 12 g.
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Molar Mass
• By definition, a molar mass is 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).
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Using Moles
Moles provide a bridge from the molecular scale to the real-world scale.
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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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Molar mass is the mass of 1 mole of in gramseggsshoes
marblesatoms
1 mole 12C atoms = 6.022 x 1023 atoms = 12.00 g
1 12C atom = 12.00 amu
1 mole 12C atoms = 12.00 g 12C
1 mole lithium atoms = 6.941 g of Li
For any element
atomic mass (amu) = molar mass (grams)
3.2
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One Mole of:
C S
Cu Fe
Hg
3.2
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1 amu = 1.66 x 10-24 g or 1 g = 6.022 x 1023 amu
1 12C atom12.00 amu
x12.00 g
6.022 x 1023 12C atoms=
1.66 x 10-24 g1 amu
3.2
M = molar mass in g/mol
NA = Avogadro’s number
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x 6.022 x 1023 atoms K1 mol K
=
Do You Understand Molar Mass?
How many atoms are in 0.551 g of potassium (K) ?
1 mol K = 39.10 g K
1 mol K = 6.022 x 1023 atoms K
0.551 g K 1 mol K39.10 g K
x
8.49 x 1021 atoms K
3.2
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Do You Understand Molecular Mass?
How many H atoms are in 72.5 g of C3H8O ?
1 mol C3H8O = (3 x 12) + (8 x 1) + 16 = 60 g C3H8O
1 mol H = 6.022 x 1023 atoms H
5.82 x 1024 atoms H
3.3
1 mol C3H8O molecules = 8 mol H atoms
72.5 g C3H8O1 mol C3H8O60 g C3H8O
x8 mol H atoms
1 mol C3H8Ox
6.022 x 1023 H atoms1 mol H atoms
x =
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KE = 1/2 x m x v2
v = (2 x KE/m)1/2
F = q x v x B3.4
Ligh
t
Ligh
t
Hea
vy
Hea
vy
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Percent composition of an element in a compound =
n x molar mass of elementmolar mass of compound
x 100%
n is the number of moles of the element in 1 mole of the compound
C2H6O
%C =2 x (12.01 g)
46.07 gx 100% = 52.14%
%H =6 x (1.008 g)
46.07 gx 100% = 13.13%
%O =1 x (16.00 g)
46.07 gx 100% = 34.73%
52.14% + 13.13% + 34.73% = 100.0%
3.5
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3.5
Percent Composition and Empirical FormulasDetermine the empirical formula of a compound that has the following percent composition by mass: K 24.75, Mn 34.77, O 40.51 percent.
nK = 24.75 g K x = 0.6330 mol K1 mol K
39.10 g K
nMn = 34.77 g Mn x = 0.6329 mol Mn1 mol Mn
54.94 g Mn
nO = 40.51 g O x = 2.532 mol O1 mol O
16.00 g O
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3.5
Percent Composition and Empirical Formulas
K : ~~ 1.00.6330
0.6329
Mn : 0.6329
0.6329= 1.0
O : ~~ 4.02.532
0.6329
nK = 0.6330, nMn = 0.6329, nO = 2.532
KMnO4
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3.6
g CO2 mol CO2 mol C g C
g H2O mol H2O mol H g H
g of O = g of sample – (g of C + g of H)
Combust 11.5 g ethanolCollect 22.0 g CO2 and 13.5 g H2O
6.0 g C = 0.5 mol C
1.5 g H = 1.5 mol H
4.0 g O = 0.25 mol O