Chapter 4.6-4.10 Types of Chemical Reactions and Solution Stoichiometry PHall AP info. NOT integrated into this presentation

Chapter 4.6-4.10

Types of Chemical

Reactions and Solution

Stoichiometry

PHall AP info. NOT integrated into this presentation

Chapter 4

Table of Contents

Copyright © Cengage Learning. All rights reserved 2

4.6 Describing Reactions in Solution

4.7Stoichiometry of Precipitation Reactions

4.8Acid–Base Reactions

4.9Oxidation–Reduction Reactions

4.10Balancing Oxidation–Reduction Equations

3

Chapter 4

Table of Contents

• Assignments - Tuesday - January 29, 2013• CW: Notes 4.6-4.10 • CW: Pre-lab for tomorrow determining %iodine in iodine

tincture using titrations• HW: Last week’s titration lab report due tomorrow• HW: Ch. 4 homework problems due Thursday• Test ch.3-4 on Friday.

Section 4.6

Describing Reactions in Solution

Return to TOC


• Gives the overall reaction stoichiometry but not necessarily the actual forms of the reactants and products in solution.

• Reactants and products generally shown as compounds.

• Use solubility rules to determine which compounds are aqueous and which compounds are solids.

AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)

Formula Equation (Molecular Equation)

Section 4.6


Return to TOC


• Represents as ions all reactants and products that are strong electrolytes.

Ag+(aq) + NO3−(aq) + Na+(aq) + Cl−(aq) →

AgCl(s) + Na+(aq) + NO3

−(aq)

Complete Ionic Equation

Section 4.6


Return to TOC


• Includes only those solution components undergoing a change. Show only components that actually react.

Ag+(aq) + Cl−(aq) → AgCl(s)

• Spectator ions are not included (ions that do not participate directly in the reaction). Na+ and NO3

− are spectator ions.

Net Ionic Equation

Section 4.6


Return to TOC


Concept Check

Write the correct formula equation, complete ionic equation, and net ionic equation for the reaction between cobalt(II) chloride and sodium hydroxide.

Formula Equation:

CoCl2(aq) + 2NaOH(aq) → Co(OH)2(s) + 2NaCl(aq)

Complete Ionic Equation:

Co2+(aq) + 2Cl−(aq) + 2Na+(aq) + 2OH−(aq) →

Co(OH)2(s) + 2Na+(aq) + 2Cl−(aq)

Net Ionic Equation:

Co2+(aq) + 2OH−(aq) → Co(OH)2(s)

Section 4.7

Stoichiometry of Precipitation Reactions

Return to TOC


1. Identify the species present in the combined solution, and determine what reaction if any occurs.

2. Write the balanced net ionic equation for the reaction.

3. Calculate the moles of reactants.

4. Determine which reactant is limiting.

5. Calculate the moles of product(s), as required.

6. Convert to grams or other units, as required.

Solving Stoichiometry Problems for Reactions in Solution

Section 4.7


Return to TOC


Concept Check (Part I)

10.0 mL of a 0.30 M sodium phosphate solution reacts with 20.0 mL of a

0.20 M lead(II) nitrate solution (assume no volume change).

1) What precipitate will form?

lead(II) phosphate, Pb3(PO4)2

2) What mass of precipitate will form?

Section 4.7


Return to TOC


• Where are we going? To find the mass of solid Pb3(PO4)2 formed.

• How do we get there? What are the ions present in the combined solution? What is the balanced net ionic equation for the

reaction? What are the moles of reactants present in the

solution? Which reactant is limiting? What moles of Pb3(PO4)2 will be formed?

What mass of Pb3(PO4)2 will be formed?

Let’s Think About It

Section 4.7


Return to TOC


Concept Check (Part I)

10.0 mL of a 0.30 M sodium phosphate solution reacts with 20.0 mL of a 0.20 M lead(II) nitrate solution (assume no volume change).

2) What mass of precipitate will form?2Na3PO4(aq) + 3Pb(NO3)2 (aq) 6NaNO3(aq) + Pb3(PO4)2 (s)

(.0100 L)(.30 mol/L) (.0200 L) (.20 mol/L)

.0030 mol .0040 mol

2:3 ratio so if you have .0030 mol you need .0045 mol, so lead II nitrate is the limiting reactant.

3:1 ratio between lead II nitrate and lead II phosphate .0040/3 = .001333 mol x 811.54 =

1.08 g = 1.1 g Pb3(PO4)2

Section 4.7


Return to TOC


Concept Check (Part II)


3) What is the concentration of nitrate ions left in solution after the reaction is complete?

Section 4.7


Return to TOC


• Where are we going? To find the concentration of nitrate ions left in

solution after the reaction is complete.

• How do we get there? What are the moles of nitrate ions present in the

combined solution? What is the total volume of the combined

solution?


Section 4.7


Return to TOC


Concept Check (Part II)10.0 mL of a 0.30 M sodium phosphate solution reacts with 20.0 mL of a 0.20 M lead(II) nitrate solution (assume no volume change).

3) What is the concentration of nitrate ions left in solution after the reaction is complete?

2Na3PO4(aq) + 3Pb(NO3)2 (aq) 6NaNO3(aq) + Pb3(PO4)2 (s)

3:6 ratio reactant and product .0040 mol produces .0080 mol of nitrate ions so

.0080 mol / (.01 + .02 L) = .0080/.03 = .26666 mol/L =0.27 M

Section 4.7


Return to TOC


Concept Check (Part III)


4) What is the concentration of phosphate ions left in solution after the reaction is complete?

Section 4.7


Return to TOC


• Where are we going? To find the concentration of phosphate ions left in

solution after the reaction is complete.

• How do we get there? What are the moles of phosphate ions present in

the solution at the start of the reaction? How many moles of phosphate ions were used

up in the reaction to make the solid Pb3(PO4)2?

How many moles of phosphate ions are left over after the reaction is complete?

What is the total volume of the combined solution?


Section 4.7


Return to TOC


Concept Check (Part III)10.0 mL of a 0.30 M sodium phosphate solution reacts with 20.0 mL of a 0.20 M lead(II) nitrate solution (assume no volume change). ???? can’t get to work out

4) What is the concentration of phosphate ions left in solution after the reaction is complete?2Na3PO4(aq) + 3Pb(NO3)2 (aq) 6NaNO3(aq) + Pb3(PO4)2(s)

.004 mol (ratio is 3:1) for lead II phosphate molecules but 2 phosphate ions for each molecule group, so .004/3 = moles of lead II phosphate molecules x 2 since 2 phosphate ions in each of the phosphate ions in products

(.004 mol/3)(2) = .002666 moles phosphate ions on product side

3:2 ratio on reactant side so .004 moles x 2/3 = .02666 moles phosphate ions used with reactant side but had .003 moles available at beginning so .0030 = .02666 = .024 moles left

.024 moles/ (.01 + .02 L) =

0.011 M

ACIDSACIDS AND BASES AND BASES

www.lab-initio.com

Section 4.8

Acid–Base Reactions

Return to TOC


• Acid—proton donor• Base—proton acceptor• For a strong acid and base reaction, the net

ionic equation is:

H+(aq) + OH–(aq) →H2O(l)

Arrhenius Acid-Base ReactionsAcids - produce H+ ions in water

Bases - produce OH- ions in solution

*OH-, hydroxide ions are so strong that they can be assumed to completely react with even a weak acid in solution

Acid–Base Reactions (Brønsted–Lowry)

Properties of AcidsProperties of Acids Acids are proton (hydrogen ion, HAcids are proton (hydrogen ion, H++) ) donorsdonors Acids have a pH lower than 7Acids have a pH lower than 7 Acids taste sourAcids taste sour Acids effect indicatorsAcids effect indicators

Blue litmus turns redBlue litmus turns red Methyl orange turns redMethyl orange turns red

Acids react with active metals, Acids react with active metals, producing Hproducing H22

Acids react with carbonates Acids react with carbonates

Acids neutralize basesAcids neutralize bases

Acids are Proton (Acids are Proton (HH++ ion) Donors ion) Donors

Strong acids are assumed to be 100% ionized in solution (good H+ donors).

Weak acids are usually less than 5% ionized in solution (poor H+ donors).

HCl H2SO4 HNO3

H3PO4 HC2H3O2 Organic acids

Acids Have Acids Have a pH less a pH less

than 7than 7

http://upload.wikimedia.org/wikipedia/commons/4/46/PH_scale.png

Acids Acids Effect Effect

IndicatorsIndicators

Blue litmus paper turns red in contact with an acid.

Methyl orange turns red with addition of an acid

Acids React with Active MetalsAcids React with Active Metals

Acids react with active metals to form Acids react with active metals to form salts and hydrogen gas.salts and hydrogen gas.

Mg + 2HCl MgCl2 + H2(g)

Zn + 2HCl ZnCl2 + H2(g)

Mg + H2SO4 MgSO4 + H2(g)

AcidsAcids React withReact with CarbonatesCarbonates

2HC2H3O2 + Na2CO3

2 NaC2H3O2 + H2O + CO2

Effects of Acid Rain on MarbleEffects of Acid Rain on Marble((calcium carbonatecalcium carbonate))

George Washington:BEFORE

George Washington:AFTER

Properties of BasesProperties of Bases Bases are proton (hydrogen ion, H+) acceptors Bases have a pH greater than 7 Bases taste bitter Bases effect indicators

Red litmus turns blue Phenolphthalein turns purple

Solutions of bases feel slippery Bases neutralize acids

Bases are Proton (Bases are Proton (HH++ ion) Acceptors ion) Acceptors

Sodium hydroxide (lye), Sodium hydroxide (lye), NaOHNaOH Potassium hydroxide, Potassium hydroxide, KOHKOH Magnesium hydroxide, Magnesium hydroxide, Mg(OH)Mg(OH)22

Calcium hydroxide (lime), Calcium hydroxide (lime), Ca(OH)Ca(OH)22

OH- (hydroxide) in base combines with H+ in acids to form water

HH++ + + OHOH-- HH22OO

Bases have Bases have a pH a pH

greater greater than 7than 7

http://upload.wikimedia.org/wikipedia/commons/4/46/PH_scale.png

Bases Effect IndicatorsBases Effect Indicators

Red litmus paper turns blue in contact with a base.

Phenolphthalein turns bright pink in a base.

Bases Neutralize AcidsBases Neutralize Acids

Milk of Magnesia contains magnesium hydroxide, Mg(OH)2, which neutralizes stomach acid, HCl.

2 HCl + Mg(OH)2 MgCl2 + 2 H2O

Acids Neutralize BasesAcids Neutralize Bases

HCl + NaOH NaCl + H2O

Neutralization reactions ALWAYS produce a salt and water.

H2SO4 + 2NaOH Na2SO4 + 2H2O

2HNO3 + Mg(OH)2 Mg(NO3)2 + 2H2O

Section 4.8


Return to TOC


Neutralization of a Strong Acid by a Strong Base

Section 4.8


Return to TOC


1. List the species present in the combined solution before any reaction occurs, and decide what reaction will occur.

2. Write the balanced net ionic equation for this reaction.

3. Calculate moles of reactants.

4. Determine the limiting reactant, where appropriate.

5. Calculate the moles of the required reactant or product.

6. Convert to grams or volume (of solution), as required.

Performing Calculations for Acid–Base Reactions

Section 4.8


Return to TOC


• Titration – delivery of a measured volume of a solution of known concentration (the titrant) into a solution containing the substance being analyzed (the analyte).

• Equivalence point – enough titrant added to react exactly with the analyte.

• Endpoint – the indicator changes color so you can tell the equivalence point has been reached.

Acid–Base Titrations

36

Section 4.8


Return to TOC

Click on the following link to watch a video and complete an interactive titration simulation to prepare for a future lab which is a bit different than the previous acid-base titration.

• http://www.kentchemistry.com/links/AcidsBases/titration.htm

• Complete the interactive activity and include answers to questions in your notes.

• You may also want to watch the video on titration above the interactive simulation.

36

http://www.kentchemistry.com/links/AcidsBases/titration.htm

http://www.kentchemistry.com/links/AcidsBases/titration.htm

Section 4.8


Return to TOC


Concept Check

For the titration of sulfuric acid (H2SO4) with sodium hydroxide (NaOH), how many moles of sodium hydroxide would be required to react with 1.00 L of 0.500 M sulfuric acid to reach the endpoint?

Section 4.8


Return to TOC


• Where are we going? To find the moles of NaOH required for the

reaction.

• How do we get there? What are the ions present in the combined

solution? What is the reaction? What is the balanced net ionic equation for the

reaction? What are the moles of H+ present in the solution? How much OH– is required to react with all of the

H+ present?


Section 4.8


Return to TOC


Concept Check

For the titration of sulfuric acid (H2SO4) with sodium hydroxide (NaOH), how many moles of sodium hydroxide would be required to react with 1.00 L of 0.500 M sulfuric acid to reach the endpoint?

H2SO4 + 2NaOH --> 2H2O + Na2SO4 2H+ + SO4

2- + 2Na+ + 2OH- --> 2H2O + 2Na+ SO42-

2H+ + 2OH---> 2H2O

1.00 L x .500 M = .500 moles (1:2 ratio) with NaOH so need 1.00 moles NaOH

1.00 mol NaOH

<Makes sense without the net

ionic equation?

40

Section 4.8


Return to TOC

STOPPED HERE FOR TUESDAY - 1-29-13 - VOER

• STILL NEED TO GO OVER OXIDATION REDUCTION REACTIONS.

41

Chapter 4

Table of Contents


tincture using titrations• HW: Last week’s titration lab report due tomorrow• HW: Ch. 4 homework problems due Thursday• Test ch.3-4 on Friday.• FINISH QUIZZES ON COMPUTER AND SHOW

SCORES

42

Chapter 4

Table of Contents

• Assignments - WEDNESDAY - January 30, 2013• Lab: Determining %iodine in iodine tincture using

titrations• CW: Discuss Pre-lab calculations if time permits.• Turn in Last week’s titration lab report in box.• HW: Ch. 4 homework problems due Thursday but will

not pick up until Friday. We have covered all but REDOX reactions.

• Test ch.3-4 on Friday.

Acid-Base Reactions

Copyright © Houghton Mifflin Company. All rights reserved. 4–

Proton TransferClick here to watch visualization

http://college.cengage.com/chemistry/zumdahl/chemistry/7e/assets/students/protected/fae/index.html?layer=act&src=qtiworkflowflash_4_18.xml&w=750&h=434


Neutralization of a Strong Acid by a Strong Base

Click here to watch visualization.



Acid-Base TitrationClick here to watch video.



Key Titration Terms

• Titrant - solution of known concentration used in titration.

• Analyte - substance being analyzed.• Equivalence point - enough titrant

added to react exactly with the analyte.• Endpoint - the indicator changes color

so you can tell the equivalence point has been reached.


Performing Calculations for Acid-Base Reactions

1. List initial species and predict reaction.

2. Write balanced net ionic reaction.

3. Calculate moles of reactants.

4. Determine limiting reactant.

5. Calculate moles of required reactant or product.

6. Convert to grams or volume, as required.

49

Chapter 4

Table of Contents

• Assignments - THURSDAY - January 31, 2013• CW: REDOX reactions • 1/2 Reactions Method of balancing REDOX rxns &

practice online activity with REDOX.• Turned in Last week’s titration lab report in box

yesterday.• HW: Ch. 4 homework problems turned in tomorrow• Test ch.3-4 tomorrow - Friday - handout review

concepts• Lab: Determining %iodine in iodine tincture using

titrations calculations for pre-lab discussed; lab report due next Wednesday.

50

Section 4.10

Balancing Oxidation–Reduction Equations

Return to TOC

Assignments - WED - OCT 8, 2013

• CW: Notes 4.9-4.10 (4.6 refresh - read 4.7-4.8)

• CW: REDOX Practice Problems & activities using computers

• *We will have additional time on Friday to complete this activity.

• HW: ch. 4 p.173-175 #57, 59a, 63, 65, 67a-e, 71a-e, 73ab, 75ab, 77 due Friday.

• HW: Iodine in iodine tincture titration Lab report due Tuesday

• TEST ch.3-4 Tuesday - Oct. 15th - Test starts at 7:30 a.m.

Oxidation-Reduction Oxidation-Reduction ReactionsReactions“Redox”“Redox”

LEO SAYS GERLEO SAYS GER

Lose Electrons = Oxidation

Gain Electrons = Reduction

OIL RIGOxidation is Loss of ElectronsReduction is Gain of Electrons

Section 4.9

Oxidation–Reduction Reactions

Return to TOC


• Reactions in which one or more electrons are transferred.

Redox Reactions

Section 4.9


Return to TOC


Reaction of Sodium and Chlorine

Oxidation Reduction ReactionsOxidation Reduction Reactions(Redox)(Redox)

Each sodium atom loses one electron:

Each chlorine atom gains one electron:

• →

• →

• →

PLEASE NOTE THAT THE circle R should be a reaction arrow and the R should NOT be here. This came from a different presentation and will not let me edit or delete the R as it was made with a PPT and converted to the MAC version. I tried to add arrows to show that this should be in it’s place by putting it on or near the R.

LEO says GER :LEO says GER :Lose Electrons = Oxidation

Sodium is oxidized

Gain Electrons = Reduction

Chlorine is reduced

OIL RIGOxidation is Loss of ElectronsReduction is Gain of Electrons

• →

• →

Section 4.9


Return to TOC


1. Oxidation state of an atom in an element = 0

2. Oxidation state of monatomic ion = charge of the ion

3. Oxygen = −2 in covalent compounds (except in peroxides where it = −1)

4. Hydrogen = +1 in covalent compounds (-1 with metals)

5. Fluorine = −1 in compounds

6. Sum of oxidation states = 0 in compounds

7. Sum of oxidation states = charge of the ion in ions

Rules for Assigning Oxidation States


Table 4.2 Rules for Assigning Oxidation States

Section 4.9


Return to TOC


Exercise

Find the oxidation states for each of the elements in each of the following compounds:

• K2Cr2O7

• CO32-

• MnO2

• PCl5• SF4

K = +1; Cr = +6; O = –2

C = +4; O = –2

Mn = +4; O = –2

P = +5; Cl = –1

S = +4; F = –1

59

Examples - assigning oxidation numbers

Assign oxidation states to all elements:

60

Examples - assigning oxidation numbers

Assign oxidation states to all elements:

0

0

-2+6 -2

-2

-2 -2 -2

-2-2

+1 -1+3

+6

+7

+5

+1+4+5

+6 +1 +1-2

Section 4.9


Return to TOC


• Transfer of electrons• Transfer may occur to form ions• Oxidation – increase in oxidation state

(loss of electrons); reducing agent• Reduction – decrease in oxidation state

(gain of electrons); oxidizing agent

Redox Characteristics

Section 4.9


Return to TOC


Concept Check

Which of the following are oxidation-reduction reactions? Identify the oxidizing agent and the reducing agent.

•Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)

•Cr2O72-(aq) + 2OH-(aq) → 2CrO4

2-(aq) + H2O(l)

a)2CuCl(aq) → CuCl2(aq) + Cu(s)

Section 4.10


Return to TOC


1. Write the unbalanced equation.

2. Determine the oxidation states of all atoms in the reactants and products.

3. Show electrons gained and lost using “tie lines.”

4. Use coefficients to equalize the electrons gained and lost.

5. Balance the rest of the equation by inspection.

6. Add appropriate states.

Balancing Oxidation–Reduction Reactions by Oxidation States

Section 4.10


Return to TOC


• Balance the reaction between solid zinc and aqueous hydrochloric acid to produce aqueous zinc(II) chloride and hydrogen gas.

Section 4.10


Return to TOC


• Zn(s) + HCl(aq) → Zn2+(aq) + Cl–(aq) + H2(g)

1. What is the unbalanced equation?

Section 4.10


Return to TOC


• Zn(s) + HCl(aq) → Zn2+(aq) + Cl–(aq) + H2(g) 0 +1 –1 +2 –1 0

2. What are the oxidation states for each atom?

Section 4.10


Return to TOC


1 e– gained (each atom)

• Zn(s) + HCl(aq) → Zn2+(aq) + Cl–(aq) + H2(g) 0 +1 –1 +2 –1 0 2 e– lost

• The oxidation state of chlorine remains unchanged.

3. How are electrons gained and lost?

Section 4.10


Return to TOC


1 e– gained (each atom) × 2

• Zn(s) + HCl(aq) → Zn2+(aq) + Cl–(aq) + H2(g) 0 +1 –1 +2 –1 0 2 e– lost

• Zn(s) + 2HCl(aq) → Zn2+(aq) + Cl–(aq) + H2(g)

4. What coefficients are needed to equalize the electrons gained and lost?

Section 4.10


Return to TOC


• Zn(s) + 2HCl(aq) → Zn2+(aq) + 2Cl–(aq) + H2(g)

5. What coefficients are needed to balance the remaining elements?

70

20.4 Oxidation # Changes

an increase in oxidation number of an atom signifies oxidation

a decrease in oxidation number of an atom signifies reduction

+2 to +4

0 to -1

71

Identifying Redox Reactions

Oxidation and reduction always occur together in a chemical reaction. For this reason, these reactions are called “redox” reactions.

Although there are different ways of identifying a redox reaction, the best is to look for a change in oxidation state:

I. Balancing Redox Reactionsby half-reaction method

STEP 1. Split Reaction into 2 Half-ReactionsSTEP 2. Balance Elements Other than H & OSTEP 3. Balance O by Inserting H2O into eqns. as necessary

STEP 4. Balance H with H+ or H2O (see 4a, 4b)STEP 5. Balance Charge by Inserting Electrons as needed

STEP 6. Multiply Each 1/2 Reaction by Factor needed to make no. of Electrons in each 1/2 Reaction Equal

STEP 7. Add Eqns. & Cancel Out Duplicate terms, where possible

I. Balancing Redox Reactions (continued)

STEP 4a. In ACID: Balance H by Inserting H+, as needed

STEP 4b. In BASE: Balance H by (i) inserting 1 H2O for each missing H & (ii) inserting same no. of OH- on OTHER SIDE OF REACTION as H2O’s added in (i)

74

Section 4.10


Return to TOC

Online Activity Problems - see handout sheet

• Balancing REDOX in acidic soln.- Problem #4 example - do this on board using rules.

• Balancing REDOX in basic soln - Problem #5 example- do this on board using rules.

• Students practice the online activities with these.

NEED TO UPDATE THIS!

75

Section 4.10


Return to TOC

Practice Problem #4 on handout sheet in acidic sol’n• Problem #4 - Redox in Acidic Solution, Overall ResultBalance the following redox equation in acidic solution

Cr2O72- + C2H4O → C2H4O2 + Cr3+

Step #1 - Write the half-reactions if Redox reaction.

Cr2O72- → Cr3+

C2H4O → C2H4O2

+3

+6

Reduction half-rxn

Oxidation half-rxn.

+3

0-1 +1

0

+1 -2-2 +3

+6

-2

-1

76

Section 4.10


Return to TOC

Practice Problem #4 on handout sheet in acidic sol’n

• Problem #4 - Redox in Acidic Solution, Overall ResultBalance the following redox equation in acidic solution

Cr2O72- + C2H4O → C2H4O2 + Cr3+

Step #2 - Balance the elements that are NOT oxygen & hydrogen

Cr2O72- → 2Cr3+

C2H4O → C2H4O2

77

Section 4.10


Return to TOC



Cr2O72- + C2H4O → C2H4O2 + Cr3+

Step #3 - Balance oxygen with water

Cr2O72- → 2Cr3+ + 7H2O

H2O + C2H4O → C2H4O2

78

Section 4.10


Return to TOC



Cr2O72- + C2H4O → C2H4O2 + Cr3+

Step #4 - Balance hydrogen with hydrogen ions, H+

14H+ + Cr2O72- → 2Cr3+ + 7H2O

H2O + C2H4O → C2H4O2 + 2H+

79

Section 4.10


Return to TOC



Cr2O72- + C2H4O → C2H4O2 + Cr3+

Step #5 - Balance charges with electrons, e-

6e- + 14H+ + Cr2O72- → 2Cr3+ + 7H2O

H2O + C2H4O → C2H4O2 + 2H+ + 2e-

80

Section 4.10


Return to TOC



Cr2O72- + C2H4O → C2H4O2 + Cr3+

Step #6 - Balance electrons lost and gained

6e- + 14H+ + Cr2O72- → 2Cr3+ + 7H2O

(3)(H2O + C2H4O → C2H4O2 + 2H+ + 2e-)

3H2O + 3C2H4O → 3C2H4O2 + 6H+ + 6e-

81

Section 4.10


Return to TOC



Cr2O72- + C2H4O → C2H4O2 + Cr3+

Step #7 - Sum the two half-reactions

6e- + 14H+ + Cr2O72- → 2Cr3+ + 7H2O

3H2O + 3C2H4O → 3C2H4O2 + 6H+ + 6e-

8H+ + Cr2O72- 3C2H4O → 3C2H4O2 + 2Cr3+ + 4H2O

82

Section 4.10


Return to TOC

Online Activity Problems

• Other information, videos, and practice problems• http://www.kentchemistry.com/aplinks/chapters/4chemrx

ns/BalancingRedox.htm

http://www.kentchemistry.com/aplinks/chapters/4chemrxns/BalancingRedox.htm

http://www.kentchemistry.com/aplinks/chapters/4chemrxns/BalancingRedox.htm

83

Section 4.10


Return to TOC

Assignments - WED - OCT 8, 2013

• CW: REDOX Practice Problems & activities using computers

• *We will have additional time on Friday to complete this activity.

• HW: Be sure all notes for ch. 4 are caught up and complete.

• HW: ch. 4 p.173-175 #57, 59a, 63, 65, 67a-e, 71a-e, 73ab, 75ab, 77 due Friday.

• HW: Iodine in iodine tincture titration Lab report due Tuesday

• TEST ch.3-4 Tuesday - Oct. 15th - Test starts at 7:30 a.m.

84

Chapter 4

Table of Contents


tincture using titrations• HW: Last week’s titration lab report due tomorrow• HW: Ch. 4 homework problems due Thursday• Test ch.3-4 on Friday.

Oxidation and Reduction (Redox)Oxidation and Reduction (Redox)

Electrons are transferred Spontaneous redox rxns can transfer energy

Electrons (electricity) Heat

Non-spontaneous redox rxns can be made to happen with electricity

Not All Reactions are Redox ReactionsNot All Reactions are Redox Reactions

Reactions in which there has been no change in oxidation number are not redox rxns.

Examples:

• →

• →

Rules for Assigning Oxidation NumbersRules for Assigning Oxidation NumbersRules 1 & 2Rules 1 & 2

1. The oxidation number of any uncombined element is zero

2. The oxidation number of a monatomic ion equals its charge

• →

Rules for Assigning Oxidation NumbersRules for Assigning Oxidation NumbersRules 3 & 4Rules 3 & 4

3. The oxidation number of oxygen in compounds is -2

4. The oxidation number of hydrogen in compounds is +1

Rules for Assigning Oxidation Rules for Assigning Oxidation Number Rule 5Number Rule 5

5. The sum of the oxidation numbers in the formula of a compound is 0

2(+1) + (-2) = 0 H O

(+2) + 2(-2) + 2(+1) = 0 Ca O H

Rules for Assigning Oxidation NumbersRules for Assigning Oxidation NumbersRule 6Rule 6

6. The sum of the oxidation numbers in the formula of a polyatomic ion is equal to its charge

X + 3(-2) = -1N O

∴X = +5 ∴X = +6

X + 4(-2) = -2S O

The Oxidation Number Rules - SIMPLIFIEDThe Oxidation Number Rules - SIMPLIFIED

1. The sum of the oxidation numbers in ANYTHING is equal to its charge2. Hydrogen in molecular compounds is +1 3. Oxygen in compounds is -2 except with perioxides

Reducing Agents and Oxidizing AgentsReducing Agents and Oxidizing Agents

The substance reduced is the oxidizing agent The substance oxidized is the reducing agent

Sodium is oxidized – it is the reducing agent

Chlorine is reduced – it is the oxidizing agent

• →

• →

Trends in Oxidation and ReductionTrends in Oxidation and Reduction

Active metals:• Lose electrons easily• Are easily oxidized• Are strong reducing agents

Active nonmetals: Gain electrons easily Are easily reduced Are strong oxidizing agents

Redox Reaction Prediction #1

Important Oxidizers Formed in reaction

MnO4- (acid solution)

MnO4- (basic solution)

MnO2 (acid solution)Cr2O7

2- (acid)CrO4

2-

HNO3, concentratedHNO3, diluteH2SO4, hot concMetallic IonsFree HalogensHClO4

Na2O2

H2O2

Mn(II)MnO2

Mn(II)Cr(III)Cr(III)NO2

NOSO2

Metallous IonsHalide ionsCl-

OH-

O2

Redox Reaction Prediction #2

Important Reducers Formed in reaction

Halide IonsFree MetalsMetalous IonsNitrite IonsSulfite IonsFree Halogens (dil, basic sol)Free Halogens (conc, basic sol)C2O4

2-

HalogensMetal IonsMetallic ionsNitrate IonsSO4

2-

Hypohalite ionsHalate ionsCO2

96

Strongest Oxidizing Agent Weakest Reducing AgentBa 2+ (aq) Ba (s)

Ca 2+ (aq) Ca (s)

Mg 2+ (aq) Mg (s)

Al 3+ (aq) Al (s)

Zn 2+ (aq) Zn (s)

Cr 3+ (aq) Cr (s)

Fe 2+ (aq) Fe (s)

Cd 2+ (aq) Cd (s)

Tl + (aq) Tl (s)

Co 2+ (aq) Co (s)

Ni 2+ (aq) Ni (s)

Sn 2+ (aq) Sn (s)

Cu 2+ (aq) Cu (s)

Hg 2+ (aq) Hg (s)

Ag 2+ (aq) Ag (s)

Pt 2+ (aq) Pt (s)

Au 1+ (aq) Au (s)

Weakest Oxidizing Agent Strongest Reducing Agent

Oxidation Reduction Table 12.2

Inquiry into Chemistry

97

Chapter 4

Table of Contents

• Assignments - FRIDAY - February 1, 2013• CW: Finish REDOX Computer Activity Problems with • 1/2 Reactions Method of balancing REDOX rxns &

practice online activity with REDOX.• Answer Questions on Ch. 4 homework problems may

turn in or keep until Monday to use for studying.• CW: Computer Link Activities and Problems *-required• Test ch.3-4- MONDAY - handout review concepts• Lab: Determining %iodine in iodine tincture using

titrations calculations for pre-lab discussed; lab report due next Wednesday.

• Discuss Pre-lab problems.

END OFOxidation-Reduction ReactionsAND Ch.4

Documents

Chapter 4.6-4.10 Types of Chemical Reactions and Solution Stoichiometry PHall AP info. NOT integrated into this presentation