3-Ch3(molekul dan senyawa).ppt

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    1

    Molecules and Compounds

    Read Chapter 3.

    Study all examples and complete all

    exercises.Complete all bold numberedproblems.

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    2

    Chapter 3 Outline

    Molecular Formula

    Molar Mass

    Empirical and MolecularFormula

    Nomenclature

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    3

    Compounds & Molecules

    NaCl,salt

    Buckyball, C60

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    4

    Compounds & Molecules

    COMPOUNDS are a combination of 2 ormore elements in definite ratios by mass.

    The character of each element is lost when

    forming a compound.

    MOLECULES are the smallest unit of acompound that retains the characteristics of

    the compound.

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    5

    MOLECULAR FORMULAS

    Formula for glycine isC2H5NO2 In one molecule there are

    2 C atoms

    5 Hatoms

    1 Natom

    2 Oatoms

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    6

    WRITING FORMULAS

    Formula

    HOCH2CH2OH

    to show atom ordering

    or in the form of a structural formula

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    7

    Molecular Modeling

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    8

    Molecular Modeling

    Ball & stick Space-filling

    Drawing of glycineC

    H

    H C

    H

    H

    O

    OHN

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    9

    Resources for

    Molecular Modeling Oxford Molecular/CAChe Scientific

    software on Saunders GeneralChemistry CD-ROM

    Rasmol and Chime on the Internet See http://www.saundercollege.com

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    10

    ELEMENTS THAT EXIST

    AS MOLECULESAllotrope ofC

    Buckyball, C60

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    11

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    12

    IONS AND IONIC COMPOUNDS

    IONS are atoms or groups of atomswith a positive or negative charge.

    Taking away an electron from an atom

    gives a CATION with a positive

    charge.

    Adding an electron to an atom gives an

    ANION with a negative charge.

    F ti f

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    13Formation ofCations & Anions

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    14

    Formation ofCations & Anions

    A cation formswhen an atom

    loses one or

    more electrons.

    An anion formswhen an atom

    gains one or

    more electrons

    Mg --> Mg2+ + 2 e- F + e- --> F-

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    PREDICTING ION CHARGES

    In general

    metals (Mg) lose electrons ---> cations

    nonmetals (F) gain electrons ---> anions

    Li1+ F1- LiF

    MONATOMIC IONS

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    Figure 3.7

    Sn4+ Pb4+Also

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    17

    METALS

    M ---> n e- + Mn+

    where n = periodic group

    Na+

    Mg2+

    Al3+

    Transition metals --> M2+ or M3+

    are most common

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    18

    NONMETALS

    NONMETAL + n e- ------> Xn-

    where n = 8 - Group number

    C4- carbideN3- nitride

    O2- oxide

    F- fluoride

    Bromine

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    19

    Groups of atoms with a charge.

    (See back of periodic chart)

    POLYATOMIC IONS

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    20

    Some Common

    Polyatomic Ions

    HNO3nitric acid

    NO3

    -

    nitrate ion

    21

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    21

    Some Common

    Polyatomic IonsNH4

    +

    ammonium ion

    One of the few commonpolyatomic cations

    22S C

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    22Some CommonPolyatomic Ions

    CO32-

    carbonate ion

    HCO3-

    bicarbonate ion

    hydrogencarbonate

    23

    S C

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    23

    Some CommonPolyatomic Ions

    PO43-

    phosphate ion

    CH3CO2-

    acetate ion

    24S C

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    24

    SO42-

    Sulfate ion

    SO32-

    Sulfite ion

    Some CommonPolyatomic Ions

    25

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    25

    NO3-

    Nitrate ion

    NO2-

    Nitrite ion

    Some CommonPolyatomic Ions

    26

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    26

    COMPOUNDS FORMED FROMIONS

    CATION + ANIONCOMPOUND

    Na+ + Cl- NaCl

    A neutral compound requires equal

    number of + and - charges.

    27

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    IONIC COMPOUNDS

    NH4+

    Cl-

    ammonium chloride,NH4Cl

    28

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    28

    Some Ionic Compounds

    Ca2+ + 2 F- CaF2Calcium fluoride

    Mg2+ + 2 NO3- Mg(NO3)2

    Magnesiumnitrate

    3 Fe2+ + 2 PO43- Fe3(PO4)2

    Iron(II) phosphate

    Calcium Fluoride

    29

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    29

    Sample Questions Predict the charges for the ions formed

    from:Se Ga

    P Sr

    Give the formula for each ion in Al2(SO4)3 Give the formula for the ionic compound

    that forms between

    Na and S

    Ga and O

    Ba and N

    Answers

    30

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    30

    Properties of Ionic CompoundsForming NaCl from Na and Cl2

    A metal atom cantransfer anelectron to a

    nonmetal. The resulting

    cation and anionare attracted toeach other by

    electrostatic

    forces.

    30

    31

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    31

    Electrostatic Forces

    The oppositely charged ions in ionic

    compounds are attracted to one another by

    ELECTROSTATIC FORCES.These forces are governed by

    COULOMBS LAW.

    32

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    Electrostatic Forces

    COULOMBS LAW

    As ion charge increases, the attractiveforce _______________.

    As the distance between ions increases,

    the attractive force ________________.This idea is important and will come

    up many times in futurediscussions!

    Force of attraction=(charge on+)(charge on-)

    (distance between ions)2

    33

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    33

    Importance of Coulombs Law

    NaCl,Na+and Cl-,

    m.p. 801 oC

    MgO,Mg2+andO2-

    m.p. 2800 oC

    AlN, Al3+

    and N3-

    m.p. 2900o

    C

    34

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    34

    Names of Compounds

    Rules for nomenclature arefound in section 3.5

    STUDY them carefully!! We will be studying

    nomenclature in the

    laboratory in Experiment MA.

    35

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    35

    Counting Atoms

    Mg burns in air (O2) to

    produce whitemagnesium oxide,MgO.

    How can we figure outhow much oxide isproduced from agiven mass ofMg?

    36

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    36

    Counting Atoms

    Chemistry is a quantitative science

    we need a counting unit.

    The MOLE 1 mole is the amount of substance

    that contains as many particles

    (atoms, molecules) as there are in12.0 g of12C.

    37

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    Particles in a Mole

    6.02 x 1023

    Avogadros Number

    Amedeo Avogadro

    1776-1856

    There is Avogadros number of

    particles in a mole of any substance.

    38

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    38

    Molein Chemistry is NOT:

    An informer / spy

    Dark spot on Cindy Crawfords upper lip

    Rodent that burrows in the ground

    A tunneling machine

    Wave break

    Spicy Mexican sauce

    39

    A l i i t

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    A mole is a convenientmeasuring tool.

    Pair Dozen Ream

    Baseballs 2 baseballs 12 baseballs 13 baseballs500

    baseballs

    Pineapples2

    Pineapples

    12

    Pineapples13 Pineapples

    500

    Pineapples

    Calculators2

    Calculators

    12

    Calculators 13 Calculators500

    Calculators

    Planets 2 Planets 12 Planets 13 Planets 500 Planets

    Bakers Dozen

    40

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    0

    Mole = mol =6.022 1023particles

    Mole

    Baseballs 6.022 1023 baseballs

    Pineapples 6.022 1023 Pineapples

    Calculators 6.022 1023 Calculators

    Planets 6.022 1023 Planets

    41

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    Just as

    1 doz eggs = 12 eggsor

    1 mol of eggs = 6.022 1023 eggs

    A mole is a Number

    1 mol of H = 6.022 1023 atoms of H

    1 mol of O = 6.022

    1023

    atoms of O1 mol of Al = 6.022 1023 atoms of Al

    1 mol of Cr = 6.022 1023 atoms of Cr

    42

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    In chemistry, the mol is

    more then just a number1 mol amu = 1.00 g

    12 2411 1.661 1012

    amu mass C g

    43

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    1 mol amu = 1.00 g

    Proof:

    1 mol = 6.022 1023

    amu = 1.661

    10-24

    g

    1 mol amu = (6.022 1023) (1.661 10-24g)= 1.00 g

    44

    M l M

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    Molar Mass1 mol of12C

    = 12.00 g of C= 6.02 x 1023 atoms

    of C

    12.00 g of12C is its

    MOLAR MASS

    Taking into account allof the isotopes of C,

    the molar mass of C is12.011 g/mol

    45

    Molar Mass

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    Molar Mass1 mol of12C = 12.00 g of C

    = 6.02 x 1023

    atoms of C12.00 g of12C is its MOLAR MASS

    Taking into account all of the isotopes of

    C, the molar mass of C is 12.011 g/mol

    Find molar

    mass fromperiodic

    table

    13

    Al

    26.9815

    atomic number

    symbol

    atomic weight

    46

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    PROBLEM: How many molesare represented by 0.200 g ofMg?

    How many atoms in this piece of Mg?

    0.200 g

    =

    1 mole

    24.3 g

    0.00823 mole

    0.00823 mole

    =

    6.02 x 1023 atom

    1 mole

    4.95 x 1021 atom

    47

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    MOLECULAR WEIGHTAND MOLAR MASS

    Molecular weight is the sum

    of the atomic weights of all atoms

    in the molecule.

    Molar mass = molecular weight

    in grams

    48

    f

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    What is the molar mass ofethanol, C2H6O?

    1 mol contains

    2 mol C (12.0 g C/1 mol) = 24.0 g C

    6 mol H (1.0 g H/1 mol) = 6.0 g H

    1 mol O (16.0 g O/1 mol) = 16.0 g O

    TOTAL = molar mass = 46.0 g/mol

    49

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    Formula =C8H9NO2

    Molar mass = 151.0 g/mol

    Tylenol

    50

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    How many moles of alcohol arethere in a standard can of beer if

    there are 21.3 g of C2H6O?

    21.3 g=

    1 mole

    46.0 g0.463 mole

    51

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    How many molecules of alcoholare there in a standard can of

    beer if there are 21.3 g of C2H6O?

    0.463 mole

    =

    6.02 x 1023

    molecule1 mole

    2.79 x 1023 molecule

    52

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    How many atoms of C are therein a standard can of beer if

    there are 21.3 g of C2H6O?

    2.79 x 1023

    molecule

    =

    2 atom C1 molecule

    5.58 x 1023 atom C

    Sample problems

    53

    Empirical and Molecular

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    Empirical and MolecularFormulas

    A pure compound always consists of thesame elements combined in the sameproportions by weight.

    Therefore, we can express molecular

    composition as PERCENT BYWEIGHT

    Ethanol, C2H6O

    52.2% C, 13% H,

    34.8% O

    54

    Percent Composition

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    Percent CompositionConsider some of the family of

    nitrogen-oxygen compounds:NO2, nitrogen dioxide and closely

    related, NO, nitrogen monoxide

    (or nitric oxide)

    Structure ofNO2 Chemistry of NO, nitrogen

    monoxide (nitric oxide)

    55

    Percen

    t Composition

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    Percent CompositionConsider NO2, Molar mass = ?

    What is the weight percent of N and of O?

    Wt.%O =2(16.0g O per mole)46.0g

    x 100%=69.6%

    Wt.% N =14.0 g N

    46.0 g NO2100% =30.4 %

    56

    Percen

    t Composition

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    Percent CompositionWhat are the weight percentages of N

    and O in NO?

    Wt. %O =16.0 g O

    30.0 g NO100%=53.3%

    Wt.% N =14.0 g N

    30.0 g NO 100% = 46.7 %

    57

    Percent Composition

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    Percent CompositionSamples Problems

    1. Calculate the percent composition of H2O.

    Wt. %O= 16.0g O

    18.0 g H2O

    100%= 88.9%

    Wt.% H =2.0 g H

    18.0 g H2O 100% = 11 %

    58

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    Percent CompositionSamples Problems

    2. Calculate the percent O in NaOH.

    Wt. %O 16.0g O

    40.0 g NaOH100%40.0%

    59

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    Percent CompositionSamples Problems

    3. Calculate the percent O and the

    percent water in CuSO4.5H2O.

    Wt. %O = 144.0g O249.6 g CuSO4 5H2O

    100%= 57.69%

    Wt. %H2O =90.0 g H2O

    249.6 g CuSO4.5H2O

    100%=36.1%

    60

    D t i i

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    Determining

    FormulasIn chemical analysis we determine

    the % by weight of each element in agiven amount of pure compound and

    derive theEMPIRICALor

    SIMPLESTformula.

    61

    A compound of B and H is

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    A compound of B and H is81.10% B. What is its empiricalformula?

    81.10 g 1 mole

    10.8 g

    18.90 g 1 mole

    1.0 g

    B H

    1.00 mole B 2.5 mole H

    7.51 mole B 19 mole H

    7.51 mole B 7.51 mole B

    2.00 mole B 5.0 mole H

    B2H

    5

    62

    A compound of B and H is 81 10% B

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    A compound of B and H is 81.10% B.

    Its empirical formula is B2H5. What is

    its molecular formula?Is the molecular formula B2H5, B4H10,

    B6H15, B8H20, etc.?

    B2

    H6

    is one example of this class of compounds.

    B2H6

    63A compound of B and H is 81.10% B.

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    A compound of B and H is 81.10% B.Its empirical formula is B2H5. What isits molecular formula?

    We need to do an EXPERIMENT to find theMOLAR MASS.

    Here experiment gives 53.3 g/mol.

    Compare with the mass of B2H5 , 26.66 g/unit

    Find the ratio of these masses.

    mol1

    HBofunits2=HBofg/unit26.66

    g/mol3.5352

    52

    Molecular formula = B4H

    10

    64

    Determine the formula of a

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    Determine the formula of acompound of Sn and I using

    the following data. Reaction of Sn and I2 is done using

    excess Sn.

    Mass of Sn in the beginning = 1.056 g

    Mass of iodine (I2) used

    = 1.947 g

    Mass of Sn remaining

    = 0.601 g

    65

    Ti d I di

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    Find the mass of Sn that combined

    with 1.947 g I2.

    Mass of Sn initially = 1.056 g

    Mass of Sn recovered = 0.601 g

    Mass of Sn used = 0.455 g

    Tin and IodineCompound

    66

    Tin and Iodine

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    0.455 g 1 mole

    118.7 g

    1.947 g 1 mole

    126.9 g

    Sn I

    1.00 mole Sn 4.01 mole I

    0.0383 mole Sn 0.1534 mole I

    0.0383 mole Sn 0.0383 mole Sn

    SnI4

    Tin and IodineCompound

    67

    More Problems

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    More Problems2. Calculate the formula for the iron sulfide

    that forms when 53.73g Fe react with

    46.27 g of sulfur.

    53.73 g 1 mole

    55.8 g

    46.27 g 1 mole

    32.1 g

    Fe S

    1.00 1.50

    0.963 1.44

    0.963 0.963

    Fe2S

    3

    2.00 3.00

    68

    More Problems

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    More ProblemsCalculate the empirical formula a compound

    containing 90.7% Pb and 9.33% O.

    90.7 g 1 mole

    207.2 g

    9.33 g 1 mole

    16.0 g

    Pb O

    1.00 1.33

    0.438 0.583

    0.438 0.438

    Pb3O

    4

    3.00 3.99

    69

    More Problems

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    More ProblemsCalculate the empirical formula for a

    compound containing 36.5% Na, 25.4% S

    and 38.1% O.

    36.5 g 1 mole

    23.0 g

    25.4 g 1 mole

    32.1 g

    Na S O

    2.01 1.00 3.01

    Na2SO

    3

    38.1 g 1 mole

    16.0 g

    1.59 0.791 2.38

    0.791 0.791 0.791

    70

    More Problems

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    More ProblemsCalculate the empirical and molecular

    formulas for nicotine, 74.0% C, 8.7% H and

    17.3% N, with a molar mass of 160 g/mole.

    74.0 g 1 mole

    12.0 g

    8.7 g 1 mole

    1.0 g

    C H N

    4.98 7.0 1.00

    17.3 g 1 mole

    14.0 g

    6.17 8.7 1.24

    1.24 1.24 1.24

    Empirical formula C5H7N

    71

    More Problems

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    More Problems7. Calculate the empirical and molecular

    formulas for nicotine, 74.0% C, 8.7% H and

    17.3% N, with a molar mass of 160 g/mole.

    Empirical formula C5H7N

    Molecular formula C10H14N2

    160= 2

    81

    72

    Practice Problems

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    Practice Problems

    Names/Formulas

    FeO

    Pb(C2H3O2)2magnesium bromide

    sodium chromate

    calcium phosphate

    ammonium carbonate

    73

    Practice Problems

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    Practice Problems

    (NH4)2SAs2O3

    SO2silicon disulfide

    As2S

    5

    dinitrogenmonoxide

    74

    Practice Problems

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    Practice Problems

    As2S3

    dinitrogenpentoxide

    silicon tetrabromidediphosphorus pentoxide

    HBrO3

    H3PO4(aq)

    H2CO3

    75

    Practice Problems

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    Practice Problems

    Calculations

    1. 26 g H2 is how many moles H2?

    2. 4.25 x 1021 molecules NH3 is howmany grams NH3?

    3. 1.5 x 102 formula units KClO3 is howmany moles KClO3

    4. 0.0042 mole Fe2O3 is how manyformula units Fe

    2

    O3

    ?

    5. 2.15 moles MgSO4.7H2O is how many g

    MgSO4.7H2O?

    76

    Practice Problems

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    Practice Problems

    6. 25 molecules HBr is how many moleHBr?

    7. .00002 g Sn is how many atoms Sn?

    8. 7.25 mole H2S is how many g H2S?

    9. 5.2 g Sr(OH)2is how many formulaunits Sr(OH)2?

    10. How many moles of CCl4 will contain2.4 g of chlorine?

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    Practice Problems

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    Practice Problems

    11. 19 g of HNO3 contains howmany

    a) molecules of HNO3? b) grams ofO?

    12. Calculate the percentcomposition of NaCl.

    13. Calculate the empirical and

    molecular formulas for acompound containing 43.7g P and56.3g O, with a molar mass of 140g/mole.

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    Practice Problems Answers

    Iron(II) oxide, ferrous oxide

    lead(II) acetate, plumbous acetate

    MgBr2 Na2CrO4 Ca3(PO4)2

    (NH4)2CO3 ammonium sulfidediarsenic trioxide sulfur dioxide

    SiS2 As2S5 N2O

    diarsenic trisulfide N2O5 SiBr4P2O5 bromic acid phosphoric acid

    carbonic acid

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    Practice Problems Answers1. 13 mole 2. 0.120 g

    3. 2.5 x 10-22 mole 4. 2.5 x 1021 atom

    5. 530. g 6. 4.2 x 10-23 mole

    7. 1 x 1017 atom 8. 247 g

    9. 2.6 x 1022 formula units

    10. 0.017 mole

    11. a) 1.8 x 1023 molecule

    b) 14 g

    12. 39.3%, 60.7% 13. C5H7N

    14. P2O5

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    Sample Questions Predict the charges for the ions formed

    from:

    Se -2 Ga +3 Al3+

    P -3 Sr +2 SO42-

    Give the formula for each ion in Al2(SO4)3 Give the formula for the ionic compound

    that forms between

    Na and S Na2S

    Ga and O Ga2O3

    Ba and N Ba3N2

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    Sample Problems

    1. 2.5 mole S = ? atom S2.5 mole

    =

    6.02 x 1023 atom

    1 mole

    1.5 x 1024 atom S

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    Sample Problems

    2. 2.1 mole Zn = ? g Zn

    2.1 mole=

    65.4 g

    1 mole140 g Zn

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    Sample Problems

    3. 1.42 g Mg = ? atom Mg

    1.42 g

    =

    1 mole

    24.3 g

    3.55 x 1022 atom

    6.02 x 1023 atom

    1 mole

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    Sample Problems

    4. 125.2 g O2

    = ? mole O2

    125.2 g=

    1 mole

    32.0 g3.91 mole O2

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    Sample Problems

    1. 1.5 mole H2O = ? g H2O

    1.5 mole=

    18.0 g

    1 mole27 g H20

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    Sample Problems

    2. 1.50 mole CCl4

    = ? molecules CCl4

    1.5 mole

    =

    6.02 x 1023 molecule

    1 mole

    9.03 x 1023 molecule

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    Sample Problems

    3. 1.25 mole CaCl2

    = ? formula units CaCl2

    1.25 mole

    =

    6.02 x 1023 formula unit

    1 mole

    7.52 x 1023 formula unit

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    Sample Problems

    4. 2.5 g K = ? g KOH

    2.5 g K

    =

    1 mole K

    39.1 g K

    3.6 g KOH

    1 mole KOH

    1 mole K

    56.1 g KOH

    1 mole KOH

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    Sample Problems

    5. 34.5 g CaCO3

    = ? g O

    34.5gCaCO3

    =

    1 moleCaCO3

    100.1gCaCO3

    16.5 g O

    3 moleO

    1 moleCaCO3

    16.0 gO

    1 moleO