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AnnouncementsAnnouncements & Agenda& Agenda (02/02/07)(02/02/07)

Quiz Today!!!Quiz Today!!!Exam NEXT FRIDAY!!!Exam NEXT FRIDAY!!! Covers Ch 1-5Covers Ch 1-5 Intermolecular Forces (Notes + bits & pieces of Ch 6)Intermolecular Forces (Notes + bits & pieces of Ch 6) Ch 7.1-7.3Ch 7.1-7.3 CHM 103 LabCHM 103 Lab

TodayToday The Mole (5.5-5.8)The Mole (5.5-5.8) Reactions Types (Especially Redox Rxns) (5.3, 5.4)Reactions Types (Especially Redox Rxns) (5.3, 5.4) Energy of Chemical Reactions (5.9)Energy of Chemical Reactions (5.9)

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Electron Electron GroupGroup

Bonded Bonded AtomsAtoms

Lone Lone PairsPairs

Bond Bond AnglesAngles

Molecular Molecular ShapeShape

ExampleExample

44 44 00 109109 tetrahedraltetrahedral CHCH44

44 33 11 ~109~109 PyramidalPyramidal NHNH33

44 22 22 ~109~109 BentBent HH22OO

Last Time: Molecular ShapesLast Time: Molecular Shapes

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Last Time: Polar MoleculesLast Time: Polar Molecules

• contain polar bonds.contain polar bonds.

• have a separation of positive and negative have a separation of positive and negative charge called a dipole indicated with charge called a dipole indicated with ++ andand --..

• have dipoles that do not cancel!have dipoles that do not cancel!

++ -- • •• •

HH–Cl–Cl H H——NN——HH

dipoledipole dipoles do dipoles do

not not cancel cancel

H

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Chapter 5!!!Chapter 5!!!Chemical ReactionsChemical Reactions

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24 Good Practice Problems (Ch 5)24 Good Practice Problems (Ch 5)

11 22 33 44 55

5.01, 5.05, 5.07, 5.11, 5.13, 5.17, 5.01, 5.05, 5.07, 5.11, 5.13, 5.17, 5.25, 5.27, 5.33, 5.37, 5.41, 5.47, 5.25, 5.27, 5.33, 5.37, 5.41, 5.47, 5.57, 5.69, 5.73, 5.75, 5.79, 5.81, 5.57, 5.69, 5.73, 5.75, 5.79, 5.81, 5.83, 5.85, 5.91, 5.93, 5.95, 5.975.83, 5.85, 5.91, 5.93, 5.95, 5.97

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Last Time: Conservation of Mass Last Time: Conservation of Mass Revisited – Balanced Reactions (Ch 5)Revisited – Balanced Reactions (Ch 5)In a In a balanced balanced chemical reactionchemical reaction

• atoms are not atoms are not gained or lost.gained or lost.

• the # of reactant the # of reactant atoms is equal to atoms is equal to the number of the number of product atoms.product atoms.

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To balance the following equation, To balance the following equation,

FeFe33OO44((ss) + H) + H22((gg) ) Fe( Fe(ss) +) + HH22O(O(ll))

• work on one element at a time.work on one element at a time.• use use onlyonly coefficients in front of formulas. coefficients in front of formulas.• do not change any subscripts.do not change any subscripts.

Fe:Fe: FeFe33OO44((ss) + H) + H22((gg) ) 3Fe3Fe((ss)) + + HH22O(O(ll))

O:O: FeFe33OO44((ss) + H) + H22((gg) ) 3Fe(3Fe(ss) +) + 44HH22OO((ll))

HH:: FeFe33OO44((ss) + ) + 4H4H22((gg)) 3Fe( 3Fe(ss) +) + 4H4H22O(O(ll))

Steps in Balancing an EquationSteps in Balancing an Equation

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Equations with Polyatomic IonsEquations with Polyatomic Ions

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Balancing with Polyatomic IonsBalancing with Polyatomic Ions

MgClMgCl22((aqaq) + Na) + Na33POPO44((aqaq) ) NaCl( NaCl(aqaq) + Mg) + Mg33(PO(PO44))22((ss))

Balance POBalance PO443- 3- as a unitas a unit

MgClMgCl22((aqaq) + ) + 22NaNa33POPO44((aqaq) ) NaCl( NaCl(aqaq) + Mg) + Mg33(PO(PO44))22((ss))

2 PO2 PO443-3- = 2 PO = 2 PO44

3-3-

Balance Mg and ClBalance Mg and Cl

33MgClMgCl22((aqaq) + ) + 22NaNa33POPO44((aqaq) ) 66NaCl(NaCl(aqaq) + Mg) + Mg33(PO(PO44))22((ss))

3 Mg3 Mg2+ 2+ = 3 Mg= 3 Mg2+2+

6 Na6 Na+ + = 6 Na= 6 Na++

6 Cl6 Cl-- = 6 Cl = 6 Cl--

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The “mole”…. Thinking about The “mole”…. Thinking about reactions on a real-world scale!reactions on a real-world scale!

1 mole is: a collection of stuff that equals the # of atoms

present in exactly 12.000 g of 12C (6.022 1023 atoms)

always 6.022 1023 somethings (Avogodro’s #, NA) New term: Molar Mass (MM)

the mass of 1 mol of an element/compound in gms. e.g. the MM of 12C is 12.000 g/mol b/c 1 mol is defined as 6.022 1023 atoms, the MM

for any element can be determined

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Collection TermsCollection Terms

A A collection termcollection term states states

a specific number of items.a specific number of items.

• 1 dozen donuts 1 dozen donuts

= 12 donuts= 12 donuts

• 1 ream of paper 1 ream of paper

= 500 sheets= 500 sheets

• 1 case 1 case = 24 cans= 24 cans

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Some One-mole QuantitiesSome One-mole Quantities

32.1 g 55.9 g 58.5 g 294.2 g 342.2 g32.1 g 55.9 g 58.5 g 294.2 g 342.2 g

One-Mole Quantities

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Avogadro’s number is used to convertAvogadro’s number is used to convert

particles of a substance to particles of a substance to moles.moles.

How many moles of COHow many moles of CO22 are in are in

2.50 x 102.50 x 102424 molecules CO molecules CO22? ?

2.50 x 102.50 x 102424 molecules CO molecules CO22 x x 1 mole CO 1 mole CO22

6.02 x 106.02 x 102323 molecules CO molecules CO22

= 4.15 mole CO= 4.15 mole CO22

Using Avogadro’s NumberUsing Avogadro’s Number

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Subscripts and MolesSubscripts and Moles

The The subscripts in a formulasubscripts in a formula show show• the relationship of atoms in the formula.the relationship of atoms in the formula.• the moles of each element in 1 mole of compound.the moles of each element in 1 mole of compound.

GlucoseGlucose

CC66HH1212OO66

In 1 molecule: 6 atoms C 12 atoms HIn 1 molecule: 6 atoms C 12 atoms H 6 atoms O6 atoms O

In 1 mole:In 1 mole: 6 mole C 6 mole C 12 mole H 12 mole H 6 mole O6 mole O

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Molar MassMolar Mass

• is the mass of one is the mass of one mole of an element mole of an element or compound.or compound.

• is the atomic mass is the atomic mass expressed in grams.expressed in grams.

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Molar Mass from Periodic TableMolar Mass from Periodic Table

Molar massMolar mass is the is the atomic mass atomic mass expressed in grams.expressed in grams.

Remember atomic masses???

1 mole Ag 1 mole C 1 mole S = 107.9 g = 12.01 g = 32.07 g

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Determining the Determining the Molar Mass…Molar Mass…

SO2

1S 32.07 g/mol

2O + 2 x 16.00 g/mol SO2 64.07 g/mol

For any molecule

molecular mass = all atomic masses

1 mole SO2 = 64.07 g SO2

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Putting the mole to work in Putting the mole to work in chemical reactions!chemical reactions!

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Molar mass factors are used to convert between the grams of a Molar mass factors are used to convert between the grams of a substance and the number of moles.substance and the number of moles.

Calculations Using Molar MassCalculations Using Molar Mass

Grams Molar mass factor Moles

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Consider the following equation:Consider the following equation:44 Fe(Fe(ss) + ) + 33 OO22((gg) ) 22 FeFe22OO33((ss))

This equation can be read in “moles” by placing theThis equation can be read in “moles” by placing theword “word “molesmoles” between each coefficient and ” between each coefficient and

formula.formula.

4 moles4 moles Fe + Fe + 3 moles3 moles O O22 2 moles2 moles Fe Fe22OO33

Reading Equations In MolesReading Equations In Moles

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Steps in Finding the Moles and Steps in Finding the Moles and Masses in a Chemical ReactionMasses in a Chemical Reaction

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The reaction between HThe reaction between H22 and O and O22 produces 13.1 g water. produces 13.1 g water.

How many grams of OHow many grams of O22 reacted? reacted?

2 H2 H22((gg) + ) + OO22((gg) ) 2 H2 H22OO ((gg) )

? g? g 13.1 g 13.1 g

The plan and factors would be The plan and factors would be

g Hg H22O mole HO mole H22O mole OO mole O22 g O g O22

molar mole-mole molarmolar mole-mole molar

mass Hmass H22O factor mass OO factor mass O22

Calculating the Mass of a ReactantCalculating the Mass of a Reactant

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Calculating the Mass of a ReactantCalculating the Mass of a Reactant

The setup would be:The setup would be:

13.1 g H13.1 g H22O x O x 1 mole H1 mole H22OO x x 1 mole O1 mole O2 2 x x 32.0 g O 32.0 g O22

18.0 g H 18.0 g H22O 2 moles HO 2 moles H22O 1 mole OO 1 mole O22

molar mole-mole molarmolar mole-mole molar

mass Hmass H22O factor mass OO factor mass O22

= 11.6 g O= 11.6 g O22

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Several Types of Reactions (5.3)Several Types of Reactions (5.3)Chemical reactions can be classified as: Chemical reactions can be classified as:

• combination reactions.combination reactions.

• decomposition reactions.decomposition reactions.

• single replacement reactions.single replacement reactions.

• double replacement reactions.double replacement reactions.

Don’t stress about these too much; be able to Don’t stress about these too much; be able to recognize the different flavors (see suggested recognize the different flavors (see suggested problems)problems)

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Oxidation-Reduction Reactions (5.4)Oxidation-Reduction Reactions (5.4)

An oxidation-reduction reaction An oxidation-reduction reaction

• provides us with energy from food.provides us with energy from food.• provides electrical energy in provides electrical energy in

batteries.batteries.• occurs when iron rusts.occurs when iron rusts.

4Fe(4Fe(ss) + 3O) + 3O22((gg) ) 2Fe 2Fe22OO33((ss))

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An oxidation-reduction reactionAn oxidation-reduction reaction

• transfers electrons from one reactant to another.transfers electrons from one reactant to another.

• loses electrons in oxidation. (LEO) loses electrons in oxidation. (LEO)

Zn(Zn(ss)) Zn Zn2+2+((aqaq)) + 2e+ 2e- - (loss of e(loss of e--))

• gains electrons in reduction. (GER)gains electrons in reduction. (GER)CuCu2+2+((aqaq) + 2e) + 2e- - Cu( Cu(ss) (gain of e) (gain of e--))

Electron Loss and GainElectron Loss and Gain

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Oxidation and ReductionOxidation and Reduction

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Write the separate oxidation and reduction reactions Write the separate oxidation and reduction reactions for the following equation.for the following equation.

2Cs(2Cs(ss) + F) + F22((gg) ) 2CsF( 2CsF(ss))

A cesium atom loses an electron to form cesium ion.A cesium atom loses an electron to form cesium ion.

Cs(Cs(ss) ) CsCs++((ss) + 1e) + 1e− − oxidationoxidation

Fluorine atoms gain electrons to form fluoride ions.Fluorine atoms gain electrons to form fluoride ions.

FF22((ss) + 2e) + 2e-- 2F 2F−−((ss) ) reductionreduction

Writing Oxidation & Reduction ReactionsWriting Oxidation & Reduction Reactions

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Cu and AgCu and Ag1+1+

Cu(s) Cu2+(aq) + 2e- oxidationOrange metal Blue

Ag1+(aq) + 2e- Ag(s) reduction Colorless Silver

COOL DEMO!COOL DEMO!

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Collision Theory of Reactions Collision Theory of Reactions

A chemical reaction occurs whenA chemical reaction occurs when

• collisions between molecules have sufficient collisions between molecules have sufficient energy to break the bonds in the reactants. energy to break the bonds in the reactants.

• bonds between atoms of the reactants (Nbonds between atoms of the reactants (N22 and and

OO22) are broken and new bonds (NO) can form. ) are broken and new bonds (NO) can form.

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3131

Activation EnergyActivation Energy

• The activation The activation energy is the energy is the minimum energy minimum energy needed for a needed for a reaction to take reaction to take place.place.

• When a collision When a collision provides energy provides energy equal to or equal to or greater than the greater than the activation energy, activation energy, product can form.product can form.

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• heat is released.heat is released.• the energy of the products the energy of the products

is less than the energy of is less than the energy of the reactants.the reactants.

• heat is a product.heat is a product.

C(s) + 2 H2(g) CH4(g) + 18 kcal

Exothermic ReactionsExothermic Reactions

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Endothermic ReactionsEndothermic Reactions

• Heat is absorbed.Heat is absorbed.• The energy of the The energy of the

products is greater than products is greater than the energy of the the energy of the reactants.reactants.

• Heat is a reactant (added).Heat is a reactant (added).

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

N2(g) + O2 (g) + 43.3 kcal 2NO(g)

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SummarySummary

Reaction Reaction Energy Energy Heat Heat TypeType Change Change in Reactionin Reaction

Endothermic Heat absorbed Endothermic Heat absorbed ReactantReactant

Exothermic Heat released Exothermic Heat released ProductProduct

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Rate of ReactionRate of Reaction

• is the speed at which reactant is used up.is the speed at which reactant is used up.

• is the speed at which product forms.is the speed at which product forms.

• increases when temperature rises because increases when temperature rises because reacting molecules move faster providing reacting molecules move faster providing more colliding molecules with energy of more colliding molecules with energy of activation.activation.

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Reaction Rate and CatalystsReaction Rate and Catalysts

A A catalystcatalyst • increases the increases the

rate of a reaction.rate of a reaction.• lowers the lowers the

energy of energy of activation. activation.

• is not used up is not used up during the during the reaction.reaction.

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Learning CheckLearning Check

State the effect of each on the rate of reaction as:State the effect of each on the rate of reaction as:

1) increases 2) decreases1) increases 2) decreases 3) no change 3) no change

A. increasing the temperature.A. increasing the temperature.

B. removing some of the reactants.B. removing some of the reactants.

C. adding a catalyst.C. adding a catalyst.

D. placing the reaction flask in ice.D. placing the reaction flask in ice.

E. increasing the concentration of one of the reactants.E. increasing the concentration of one of the reactants.