Ch9-Stoichiometry 2

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    1

    Stoichiometry

    Chapter 9

    StoichiometryChapter 9

    Version 1.0

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    Objectives

    Define stoichiometry

    Solve stoichiometric problems involving

    mole-ratio method

    Mass-mass relation

    Mass-volume relation

    Volume-volume relation

    Define excess reagent, limiting reagent, and

    percent yield

    Differentiate theoretical from actual yield 2

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    A Short ReviewA Short Review

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    The molar mass of an element is its

    atomic mass in grams. It contains 6.022 x 1023 atoms

    (Avogadros number) of the element.

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    The molar mass of an element or compound isthe sum of the atomic masses of all its atoms.

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    Formula Weight

    Formula weightFormula weight: the sum of the atomicweights in atomic mass units (amu) of all

    atoms in a compounds formula:

    Ionic Compounds

    Sodium chloride (NaCl) 23.0 amu Na + 35.5 amu Cl = 58.5 amu

    Aspirin (C9H8O4) 9(12.0 amu C) + 8(1.0 amu H) +4(16.0 amu O) = 180.0 amu

    Water (H2O) 2(1.0 amu H) + 16.0 amu O = 18.0 amu

    Nickel(II) chloride hydrate(NiCl26H2O)

    58.7 amu Ni + 2(35.5 amu Cl) +12(1.0) amu H) + 6(12.0 amu O) = 237.7 amu

    Molecular Compounds

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    Formula Weight

    Formula weightFormula weight can be used for both ionicand molecular compounds; it tells nothing

    about whether a compound is ionic or

    molecular. Molecular weightMolecular weight should be used only for

    molecular compounds.

    For comparison, we use formula weight forionic compounds and molecular weight for

    molecular compounds.

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    grams of a substancemolar mass =number of moles of the substance

    grams of a monoatomic elementmolar mass =number of moles of the element

    23number of moleculesnumber of moles =

    6.022 x 10 molecules/mole

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    Avogadros

    Number ofParticles

    6 x 1023

    Particles

    Molar Mass

    1 MOLE

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    2 2Al + Fe2O3 Fe + Al2O3

    For calculations of mole-mass-volume

    relationships.

    The chemical equation mustbe balanced.

    2 mol 2 mol1 mol 1 mol

    The equation is balanced.

    The number in front of a formula

    represents the number of moles of the

    reactant or product.

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    Stoichiometry: The area of chemistry

    that deals with the quantitativerelationships between reactants and

    products.

    Mole Ratio: a ratio between the molesof any two substances involved in a

    chemical reaction.

    The coefficients used in mole ratioexpressions are derived from the

    coefficients used in the balanced

    equation.

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    Stoichiometry

    Stoichiometry:Stoichiometry: the study of mass relationshipsin chemical reactions

    following is an overview of the types of

    calculations we study

    M o l e s o f AG r a m s o f AG r a m s o f BM o l e s o f B

    F r o m m o l e s t o m o l e s ,u s e t h e c o e f f i c i e n t s i n

    t h e b a l a n c e d e q u a t i o na s a c o n v e r s i o n f a c t o r

    F r o m g r a m s t o m o l e s ,u s e m o l a r m a s s ( g / m o l )

    a s a c o n v e r s i o n f a c t o r

    F r o m m o l e s t o g r a m s ,u s e m o l a r m a s s ( g / m o l )

    a s a c o n v e r s i o n f a c t o r

    Y o u a r e g i v e n o n e o f t h e s e A n d a s k e d t o f i n d o n e o f t h e s e

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    ExamplesExamplesExamplesExamples

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    2

    23 m

    1 mol

    olH

    N

    N2 + 3H2 2NH31 mol 2 mol3 mol

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    1 mol 2 mol3 mol

    N2 + 3H2 2NH3

    2

    32 mo

    3 molH

    l NH

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    The mole ratio is used to convert thenumber of moles of one substance to

    the corresponding number of moles of

    another substance in a stoichiometryproblem.

    The mole ratio is used in the solution of

    every type of stoichiometry problem.

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    Stoichiometry

    Problem: how many grams of nitrogen, N2, arerequired to produce 7.50 g of ammonia, NH3

    first find how many moles of NH3 are in7.50 g of NH3

    next find how many moles of N2 arerequired to produce this many moles of NH3

    7.50 g NH3 x1 mol NH3

    17.0 g NH3= mol NH3

    7.50 g NH3 x1 mol NH3

    17.0 g NH3

    x1 mol N2

    2 mol NH3= mol N2

    N2 (g) + 2NH3 ( g)3H2 (g)

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    Stoichiometry

    Finally convert moles of N2 to grams of N2and now do the math

    x28.0 g N2

    1 mol N2= 6.18 g N27.50 g NH3 x

    1 mol NH3

    17.0 g NH3

    x1 mol N2

    2 mol NH3

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    Identify the starting substance from the

    data given in the problem statement.

    Convert the quantity of the starting

    substance to moles, if it is not already

    done.1 mole

    moles = gramsmolar mass

    Step 1. Determine the number of moles of starting

    substance.

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    The number of moles of each substance in the

    balanced equation is indicated by thecoefficient in front of each substance. Use

    these coefficients to set up the mole ratio.

    moles of desired substance in the equationmole ratio =

    moles of starting substance in the equation

    Step 2. Determine the mole ratio of the desired

    substance to the starting substance.

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    moles of desired substance

    in the equationmoles of desired substance = moles of starting substance

    moles of starting substance

    in the equation

    Step 2. Determine the mole ratio of the desired

    substance to the starting substance.

    Multiply the number of moles of starting

    substance (from Step 1) by the mole ratio

    to obtain the number of moles of desired

    substance.

    h f ll i i h l f bCl

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    moles of desired substance in the equationmoles of desired substance = moles of starting substance

    moles of starting substance in the equation

    In the following reaction how many moles of PbCl2are formed if 5.000 moles of NaCl react?

    2NaCl(aq) + Pb(NO3)2(aq) PbCl2(s) + 2NaNO3(aq)

    5.000 moles NaCl2moles of PbCl = 22.500 mol PbCl2

    1 mol PbCl

    2 mol NaCl

    =

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    Step 3. Calculate the desired substance in the

    units specified in the problem.

    If the answer is to be in moles, the

    calculation is complete

    If units other than moles are wanted,

    multiply the moles of the desired substance

    (from Step 2) by the appropriate factor to

    convert moles to the units required.

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    Step 3. Calculate the desired substance in the

    units specified in the problem.

    molar mass1. To calculate : grams =gr moles x

    1 moams

    l

    22 2

    2

    18.02 g H O90.10 grams H O = 5.000 mol H O

    1 mol H

    O

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    236.022 x 10 atoms

    2. To calculate : atoms = moles1 mo

    atomsl

    2324 6.022 x 10 Na atoms3.011 x 10 Na atoms = 5.000 moles Na atoms

    1 mol Na atoms

    Na

    Step 3. Calculate the desired substance in the

    units specified in the problem.

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    236.022 x 10 molecules

    3. To calculate : molecules =mol moles x1 mol

    ecules

    2324 2

    2 2

    2

    6.022 x 10 H O molecules3.011 x 10 molecules H O = 5.000 moles H O

    1 mol H O

    Step 3. Calculate the desired substance in the

    units specified in the problem.

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    Stoichiometry

    Problem 1. What mass of aluminum oxide isrequired to prepare 27 g of aluminum?

    Problem 2. How many grams each of CO22

    and NH33

    are produced from 0.83 mol of

    urea?

    Al2O3 ( s)electrolysis Al(s) + O2 ( g)

    (NH2 )2CO(aq) + 2NH3 (aq) + CO2 (g)H2O

    Urea

    urease

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    Mole-MoleMole-MoleCalculationsCalculations

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    Phosphoric Acid

    Phosphoric acid (H3PO4) is one of the most

    widely produced industrial chemicals in the

    world.

    Most of the worlds phosphoric acid is

    produced by the wet process which involves

    the reaction of phosphate rock, Ca5(PO4)3,F

    with sulfuric acid (H2SO4).

    Ca5(PO4)3F(s) + 5H2SO4 3H3PO4 + HF + 5CaSO4

    C l l t th b f l f h h i id

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    Mole Ratio

    Calculate the number of moles of phosphoric acid

    (H3PO4) formed by the reaction of 10 moles of sulfuric

    acid (H2SO4).

    Ca5(PO4)3F + 5H2SO4 3H3PO4 + HF + 5CaSO4

    Step 1 Moles starting substance: 10.0 mol H2SO4

    Step 2 The conversion needed is

    moles H2SO4 moles H3PO4

    1 mol 5 mol 3 mol 1 mol 5 mol

    3 42 4

    2 4

    3 mol H PO10 mol H SO x =

    5 mol H SO3 4

    6 mol H PO

    C l l t th b f l f lf i id

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    Step 2 The conversion needed is

    moles Ca5(PO4)3F moles H2SO4

    Calculate the number of moles of sulfuric acid

    (H2SO4) that react with 10 moles of Ca5(PO4)3F.

    Ca5(PO4)3F + 5H2SO4

    3H3PO4 + HF + 5CaSO4

    Mole Ratio

    Step 1 The starting substance is 10.0 mol Ca5(PO4)3F

    1 mol 5 mol 3 mol 1 mol 5 mol

    2 45 4 3

    5 4 3

    5 mol H SO10 mol Ca (PO ) F x =

    1 mol Ca (PO ) F2 450 mol H SO

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    Mole-Mass CalculationsMole-Mass Calculations

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    1. The object of this type of problem is

    to calculate the mass of onesubstance that reacts with or is

    produced from a given number of

    moles of another substance in achemical reaction.

    2. If the mass of the starting substance

    is given, we need to convert it to

    moles.

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    3. We use the mole ratio to convert

    moles of starting substance to molesof desired substance.

    4. We can then change moles of desiredsubstance to mass of desired

    substance if called for by the

    problem.

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    ExamplesExamplesExamplesExamples

    Calculate the number of moles of H SO necessary to

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    38Mole Ratio

    2 4

    3 4

    5 mol H SO=

    3 mol H PO

    Calculate the number of moles of H2SO4 necessary to

    yield 784 g of H3PO4.

    Ca5(PO4)3F+ 5H2SO4

    3H3PO4 + HF + 5CaSO4Method 1 Step by Step

    Step 1 The starting substance is 784 grams of H3PO4.

    Step 2 Convert grams of H3PO4 to moles of H3PO4.

    Step 3 Convert moles of H3PO4 to moles of H2SO4 by themole-ratio method.

    3 4

    3 4

    1 mol H PO=

    98.0 g H PO

    3 48.00 mol H PO

    2 413.3 mol H SO

    3 4784 g H PO

    3 48.00 mol H PO

    Calculate the number of moles of H SO necessary to

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    Mole Ratio

    2 4

    3 4

    5 mol H SO=

    3mol H PO

    Calculate the number of moles of H2SO4 necessary to

    yield 784 g of H3PO4

    Ca5(PO4)3F+ 5H2SO4

    3H3PO4 + HF + 5CaSO4Method 2 Continuous

    grams H3PO4 moles H3PO4 moles H2SO4

    The conversion needed is

    3 4

    784 g H PO 3 4

    3 4

    1 mol H PO

    98.0 g H PO

    2 413.3 mol H SO

    Calculate the number of grams of H required to form

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    2

    36.0

    40

    Method 1 Step by Step

    Step 1 The starting substance is 12.0 moles of NH3

    Step 2 Calculate moles of H2 by the mole-ratio method.

    Step 3 Convert moles of H2 to grams of H2.

    Calculate the number of grams of H2 required to form

    12.0 moles of NH3.

    N2 + 3H2

    2NH3

    312.0 mol NH 218.0 mol H

    2

    1

    8.0

    Mole Ratio

    2

    3

    3 mol H=

    2 mol NH

    22

    2.0

    2g

    1m

    ol

    =

    Calculate the number of grams of H required to form

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    Mole Ratio

    2

    3

    3 mol H

    2 mol NH

    moles NH3 moles H2 grams H2

    Calculate the number of grams of H2 required to form

    12.0 moles of NH3.

    N2 + 3H2

    2NH3Method 2 Continuous

    The conversion needed is

    312.0 mol NH2

    2

    2.02 gH=

    1mol H

    236.0 g H

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    Mass-Mass CalculationsMass-Mass Calculations

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    Solving mass-mass stoichiometry problems

    requires all the steps of the mole-ratiomethod.

    1. The mass of starting substance is

    converted to moles.

    2. The mole ratio is then used to determine

    moles of desired substance.

    3. The moles of desired substance are

    converted to mass of desired substance.

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    Mass-mass Relations

    44

    g

    u

    g

    ugu

    NN

    MmMmmm =

    mu = mass of unknown substancemg = mass of given substance

    Mmu = molar mass of the given substance

    Mmg = molar mass of the given substance

    Nu = coefficient of the unknown in the balanced

    equation

    Ng = coefficient of the given substance in the

    balanced equation

    Calculate the number of grams of NH formed by the

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    Calculate the number of grams of NH3 formed by the

    reaction of 112 grams of H2.

    N2

    + 3H2

    2NH3Method 1 Step by Step

    Step 1 The starting substance is 112 grams of H2. Convert

    112 g of H2 to moles.

    grams moles2

    2

    1 mol H

    2.02 gH

    =

    2112 g H 255.4 moles H

    Step 2 Calculate the moles of NH3 by the mole ratio method.

    3

    2

    2 mol NH=

    3 mol H

    255.4 moles H 336.9 moles NH

    Calculate the number of grams of NH formed by the

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    Calculate the number of grams of NH3 formed by the

    reaction of 112 grams of H2.

    N2

    + 3H2

    2NH3Method 1 Step by Step

    Step 3 Convert moles NH3 to grams NH3.

    moles grams

    336.9 moles NH3

    3

    17.0 g NH =1 mol NH

    3629 g NH

    Calculate the number of grams of NH formed by the

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    Calculate the number of grams of NH3 formed by the

    reaction of 112 grams of H2.

    N2

    + 3H2

    2NH3

    grams H2 moles H2 moles NH3 grams NH3

    2

    2

    1 mol H2.02 g H

    2112 gH 32

    2 mol NH3 mol H

    Method 2 Continuous

    3

    3

    17.0 g NH =1 mol NH

    3629 g NH

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    Mass-VolumeMass-VolumeCalculationsCalculations

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    Mass-volume Relations

    Remember:1 mole of any substance occupies 22.4 L

    Gases are assumed to behave as ideal

    gasesThe reaction must take place at STP

    (standard temperature and pressure)

    where T = 0o C = 273 KP = 1 atm = 760 mm Hg

    As gas not in STP must be converted to49

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    Mole-Volume CalculationsMole-Volume Calculations

    Mass-Volume CalculationsMass-Volume Calculations

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    Mass-volume Relations

    53

    giveng

    u

    g

    gumol1

    L4.22

    N

    N

    Mm

    1mvol =

    L22.4mol1

    NNMmvm given

    g

    uugu =

    For unknown volume

    For unknown mass

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    Mass-volume Relations

    54

    volu = volume of unknown substance

    mu = mass of unknown substance

    mg = given mass

    vg = given volumeMmg = molar mass of the given substance

    Mmu = molar mass of the unknown substance

    Nu

    = coefficient of the unknown in the balanced

    equation

    Ng = coefficient of the given substance in the

    balanced equation

    What volume of oxygen (at STP) can be formed

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    Step 1 Write the balanced equation

    2 KClO3 2 KCl + 3 O2

    Step 2 The starting amount is 0.500

    mol KClO3. The conversion is

    moles KClO3 moles O2 liters O2

    What volume of oxygen (at STP) can be formed

    from 0.500 mol of potassium chlorate?

    What volume of oxygen (at STP) can be formed

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    2

    3

    3 mol O

    2 mol KClO

    Step 3. Calculate the moles of O2, using the

    mole-ratio method.

    3(0.500 mol KClO )

    What volume of oxygen (at STP) can be formed

    from 0.500 mol of potassium chlorate?

    Step 4. Convert moles of O2 to liters of O2

    2= 0.750 mol O

    2(0.750 mol O )22.4 L

    1 mol

    2= 16.8 L O

    2 KClO3 2KCl + 3 O2

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    Volume-VolumeVolume-VolumeCalculationsCalculations

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    Volume-volume Relations

    59

    g

    ugu

    N

    Nvv =

    This can be solved by ratio and proportion

    vu= volume of unknown substance

    vg= volume of given substance

    Nu

    = number of moles of unknown substance from

    the balanced equation

    ng = number of moles of given substance from the

    balanced equation

    For reacting gases at constant temperature and

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    H2(g) + Cl2(g) 2HCl(g)

    1 mol H2 1 mol Cl2 2 mol HCl22.4 L

    STP

    22.4 L

    STP

    2 x 22.4 L

    STP

    1 volume 1 volume 2 volumes

    Y volume Y volume 2Y volumes

    g g p

    pressure: Volume-volume relationships are the same

    as mole-mole relationships.

    What volume of oxygen will react with 150 L of

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    yg

    hydrogen to form water vapor? What volume of water

    vapor will be formed?

    2H2(g) + O2(g)

    2H2O(g)

    Assume that both reactants and products are measured at

    STP. Calculate by using reacting volumes:

    2 mol 1 mol 2 mol

    2 x 22.4 L 22.4 L 2 x 22.4 L

    2 volumes 1 volume 2 volumes

    What volume of oxygen will react with 150 L of

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    yg

    hydrogen to form water vapor? What volume of water

    vapor will be formed?

    2H2(g) + O2(g) 2H2O(g)

    ( ) 22

    22 OL75

    Hvol2Ovol1HL150 =

    ( ) OHL150Hvol2

    OHvol2HL150 2

    2

    22 =

    What volume of nitrogen will react with 600. mL of

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    g

    hydrogen to form ammonia? What volume of

    ammonia will be formed?

    N2(g) + 3H2(g) 2NH3(g)

    2600. ml H 2

    2

    1 vol N3 vol H

    2= 200. mL N

    2600. ml H3

    2

    2 vol NH3 vol H

    3= 400. mL NH

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    Limiting-Reactant andLimiting-Reactant andYield CalculationsYield Calculations

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    Limiting Reactant/ReagentLimiting Reactant/ReagentLimiting Reactant/ReagentLimiting Reactant/Reagent

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    It is called the limiting reactant

    because the amount of it present isinsufficient to react with the amounts

    of other reactants that are present.

    The limiting reactant limits the amountof product that can be formed.

    The limiting reactant/reagent is one of

    the reactants in a chemical reaction.

    How many bicyclesFrom eight wheels four

    From four frames fourFrom three pedal assemblies

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    can be assembled

    from the parts

    shown?

    bikes can be constructed.bikes can be constructed.three bikes can be constructed.

    The limiting part is thenumber of pedal

    assemblies.

    9.2

    H + Cl 2HCl

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    H2 + Cl2 2HCl

    +

    7 molecules H2 can

    form 14 molecules HCl

    4 molecules Cl2 can form

    8 molecules HCl 3 molecules of H2 remain

    H2 is in excess

    Cl2 is the limiting

    reactant9.3

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    Steps Used to Determine theSteps Used to Determine theLimiting ReactantLimiting ReactantSteps Used to Determine theSteps Used to Determine theLimiting ReactantLimiting Reactant

    1 Calculate the amount of product (moles or

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    1. Calculate the amount of product (moles or

    grams, as needed) formed from each

    reactant.2. Determine which reactant is limiting. (Thereactant that gives the least amount of

    product is the limiting reactant; the other

    reactant is in excess.3. Calculate the amount of the other reactant

    required to react with the limiting reactant,

    then subtract this amount from the startingquantity of the reactant. This gives the

    amount of the substance that remains

    unreacted.

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    ExamplesExamplesExamplesExamples

    How many moles of HCl can be produced by reacting

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    4.0 mol H2 and 3.5 mol Cl2? Which compound is the

    limiting reagent?

    Step 1 Calculate the moles of HCl that can form

    from each reactant.

    24.0 mol H

    2

    2 mol HCl1 mol H

    =

    8.0 mol HCl

    23.5 mol Cl

    2

    2 mol HCl

    1 mol Cl

    =

    7.0 mol HCl

    H2 + Cl2 2HCl

    Step 2 Determine the limiting reactant.

    The limiting reactant is Cl2because it

    producesless HCl than H2.

    How many grams of silver bromide (AgBr) can be

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    formed when solutions containing 50.0 g of MgBr2

    and 100.0 g of AgNO3 are mixed together? How

    many grams of the excess reactant remain unreacted?

    Step 1 Calculate the grams of AgBr that can form

    from each reactant.

    MgBr2(aq) + 2AgNO3 (aq) 2AgBr(s) + Mg(NO3)2(aq)

    The conversion needed is

    g reactant mol reactant mol AgBr g

    AgBr( )250.0 g MgBr 102 g AgBr

    2

    2

    1 mol MgBr

    184.1 g MgBr

    2

    2 mol AgBr

    1 mol MgBr

    187.8 g AgBr

    1 mol AgBr

    =

    ( )3100.0 g AgNO 110.5 g AgBr3

    3

    1 mol AgNO

    169.9 g AgNO

    3

    2 mol AgBr

    2 mol AgNO

    187.8 g AgBr

    1 mol AgBr

    =

    How many grams of silver bromide (AgBr) can be

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    formed when solutions containing 50.0 g of MgBr2

    and 100.0 g of AgNO3 are mixed together? How

    many grams of the excess reactant remain unreacted?

    Step 2 Determine the limiting reactant.

    MgBr2(aq) + 2AgNO3 (aq) 2AgBr(s) + Mg(NO3)2(aq)

    ( )250.0 g MgBr 102 g AgBr2

    2

    1 mol MgBr

    184.1 g MgBr

    2

    2 mol AgBr

    1 mol MgBr

    187.8 g AgBr

    1 mol AgBr

    =

    ( )3100.0 g AgNO 110.5 g AgBr3

    3

    1 mol AgNO

    169.9 g AgNO

    3

    2 mol AgBr

    2 mol AgNO

    187.8 g AgBr

    1 mol AgBr

    =

    The limiting reactant is MgBr2 because it

    forms less Ag Br.

    How many grams of the excess reactant (AgNO3)

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    remain unreacted?

    Step 3 Calculate the grams of unreacted AgNO3.

    First calculate the number of grams of

    AgNO3 that will react with 50 g of MgBr2.

    MgBr2

    (aq) + 2AgNO3

    (aq)

    2AgBr(s) + Mg(NO3

    )2

    (aq)

    ( )250.0 g MgBr 392.3 g AgNO22

    1 mol MgBr

    184.1 g MgBr

    3

    2

    2 mol AgNO

    1 mol MgBr

    3

    3

    169.9 g AgNO

    1 mol AgNO

    =

    The conversion needed is

    g MgBr2 mol MgBr2 mol AgNO3 g AgNO3

    The amount of MgBr2 that remains is

    100.0 g AgNO3

    - 92.3 g AgNO3

    = 7.7 g AgNO3

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    Reaction YieldReaction YieldReaction YieldReaction Yield

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    The quantities of products calculated

    from equations represent the maximumyield (100%) of product according to the

    reaction represented by the equation.

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    Many reactions fail to give

    a 100% yield of product.

    This occurs because of side reactions

    and the fact that many reactions are

    reversible.

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    The theoretical yield of a reaction isthe calculated amount of product that

    can be obtained from a given amount

    of reactant. The actual yield is the amount of

    product finally obtained from a given

    amount of reactant.

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    The percent yield of a reaction is theratio of the actual yield to the theoretical

    yield multiplied by 100.

    actual yieldx 100 = percent yield

    theoretical yield

    Silver bromide was prepared by reacting 200.0 g of

    i b id d d f il

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    187.8 g AgBr

    1 mol AgBr

    =

    magnesium bromide and an adequate amount of silver

    nitrate. Calculate the percent yield if 375.0 g of silver

    bromide was obtained from the reaction:MgBr2(aq) + 2AgNO3 (aq) 2AgBr(s) + Mg(NO3)2(aq)

    Step 1 Determine the theoretical yield by

    calculating the grams of AgBr that can beformed.

    The conversion needed is

    g MgBr2 mol MgBr2 mol AgBr g AgBr

    ( )2200.0 g MgBr 408.0 g AgBr2

    2

    1 mol MgBr

    184.1 g MgBr

    2

    2 mol AgBr

    1 mol MgBr

    Silver bromide was prepared by reacting 200.0 g of

    i b id d d f il

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    magnesium bromide and an adequate amount of silver

    nitrate. Calculate the percent yield if 375.0 g of silver

    bromide was obtained from the reaction:MgBr2(aq) + 2AgNO3 (aq) 2AgBr(s) + Mg(NO3)2(aq)

    Step 2 Calculate the percent yield.

    actual yieldpercent yield = x 100

    theoretical yield

    percent yield =375.0 g AgBr

    x 100 =408.0 g AgBr

    91.9%

    must have same units

    must have same units

    Solve the following problems correctly.

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    g p y

    1. Given the equation

    Al4C3 + 12 H2O 4 Al(OH)3 + 3 CH4

    a. How many moles of water are needed to react

    with 100 g of Al4C3 ?

    b. How many moles of Al(OH)3 will be produced

    when 0.600 mol of CH4 is formed?

    2. How many grams of zinc phosphate are formed

    when 10.0 g of Zn are reacted with phosphoric

    acid?

    3 Zn + 2 H3PO4 Zn3(PO4)2 + 3 H2 83

    Solve the following problems correctly.1 Gi th ti

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    1. Given the equation

    4 FeS2 + 11 O2 2 Fe2O3 + 8 SO2

    a. How many moles ofFe2O3 can be made from 1.00 mol

    of FeS2?

    b. How many moles of O2

    are required to react with

    4.5 mol of FeS2?

    c. If the reaction produces 1.55 mol ofFe2O3 , how

    many mol of SO2

    are produced?

    d. How many grams of SO2 can be formed from 0.512

    mol of FeS2?

    e. How many grams of FeS2 are needed to produce 22184

    In the following equations, determine which reactant

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    is the limiting reactant and which reactant is in excess.

    1. 2 Bi(NO3)3 + 3 H2S Bi2S3 + 6 HNO3

    50.0 g 6.00 g

    2. 3 Fe + 4 H2O Fe3O4 + 4 H2

    40.0 g 16.0 g

    85

    In the following equations, determine which reactant

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    is the limiting reactant and which reactant is in excess.

    Acetylene (C2H2) can be manufactured bythe reaction of water and calcium carbide,

    CaC2:

    CaC2 + 2 H2O C2H2 + Ca(OH)2

    When 44.5 g of commercial grade (impure)

    calcium carbide is reacted, 0.540 mol of C2H2, isproduced. Assuming that all CaC2 was reacted to

    C2H2 , what is the percent of CaC2 in the

    commercial grade material?86

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