CHAPTER 4 Reactions in Aqueous Solutions. Aqueous Solutions aqueous solutions -solute dissolved in...

CHAPTER 4CHAPTER 4

Reactions in Aqueous Reactions in Aqueous Solutions Solutions

Aqueous Solutions Aqueous Solutions aqueous solutions -solute dissolved in wateraqueous solutions -solute dissolved in water

nonelectrolytes - aqueous solutions do not nonelectrolytes - aqueous solutions do not conduct electricityconduct electricity

CC22HH55OH - ethanolOH - ethanol

CH3 CH2OH

Aqueous Solutions Aqueous Solutions CC66HH1212OO66 - glucose (blood sugar) - glucose (blood sugar)

C

OC

C

C C

C

H

H

OH

H OH

OH

H

OH

OH H

Aqueous Solutions Aqueous Solutions CC1212HH2222OO1111 - sucrose (table sugar) - sucrose (table sugar)

C

OC

C

C C

CH

2

H

H

OH

H

OH

OH

HO

H

OH

C C

C

O

C

CH2

H

OH

H

OH

H

H

OH

Molecular compounds in water (e.g., CHMolecular compounds in water (e.g., CH33OH): OH): no ions are formed.no ions are formed.

If there are no ions in solution, there is If there are no ions in solution, there is nothing to transport electric charge.nothing to transport electric charge.

Properties of Aqueous Solution

Ionic Compounds in WaterIonic Compounds in Water

Ions dissociate in water.Ions dissociate in water.

In solution, each ion is surrounded by water In solution, each ion is surrounded by water molecules.molecules.

Transport of ions through solution causes Transport of ions through solution causes flow of current.flow of current.


Strong electrolytes: completely dissociate in Strong electrolytes: completely dissociate in solution.solution.For example:For example:

Weak electrolytes: produce a small Weak electrolytes: produce a small concentration of ions when they dissolve.concentration of ions when they dissolve.These ions exist in These ions exist in equilibriumequilibrium with the with the unionized substance.unionized substance.For example:For example:


HCl(aq) H+(aq) + Cl-(aq)

HC2H3O2(aq) H+(aq) + C2H3O2-(aq)


strong electrolytes - extremely good strong electrolytes - extremely good conductors of electricityconductors of electricity

HCl, HNOHCl, HNO33, etc., etc. strong soluble acidsstrong soluble acids

NaOH, KOH, etc.NaOH, KOH, etc.strong soluble basesstrong soluble bases

NaCl, KBr, etc.NaCl, KBr, etc.soluble ionic saltssoluble ionic saltsionize in water essentially 100%ionize in water essentially 100%


weak electrolytesweak electrolytes

CHCH33COOH, (COOH)COOH, (COOH)22 weak acidsweak acids

NHNH33, Fe(OH), Fe(OH)33 weak basesweak bases

some soluble covalent saltssome soluble covalent saltsionize in water much less than 100%ionize in water much less than 100%

Strong and Weak Acidsacids generate Hacids generate H++ in aqueous solutions in aqueous solutions

strong acids ionize 100% in waterstrong acids ionize 100% in water

Strong and Weak Acidsacids generate Hacids generate H++ in aqueous solutions in aqueous solutions

strong acids ionize 100% in waterstrong acids ionize 100% in water

-

aq3aqOH

3

-aq3aq3

100%2 3

NO + H HNO

or

NO + OH OH HNO

2

-aqaq

%100g Cl H HCl

Strong and Weak Acids

entire list of strong water soluble entire list of strong water soluble acidsacids

HCl - hydrochloric acidHCl - hydrochloric acidHBr - hydrobromic acidHBr - hydrobromic acidHI - hydroiodic acidHI - hydroiodic acid

HNOHNO33 - nitric acid - nitric acid

HH22SOSO44 - sulfuric acid - sulfuric acid

HClOHClO33 - chloric acid - chloric acid

HClOHClO44 - perchloric acid - perchloric acid

Strong and Weak Acidsweak acids ionize less than 100% in waterweak acids ionize less than 100% in water

10% or less!10% or less!

some common weak acidssome common weak acidsHF - hydrofluoric acidHF - hydrofluoric acid

CHCH33COOH - acetic acid (vinegar)COOH - acetic acid (vinegar)

HH22COCO33 - carbonic acid (soda water) - carbonic acid (soda water)

HH22SOSO33 - sulfurous acid - sulfurous acid

HNOHNO22 - nitrous acid - nitrous acid

HH33POPO44 - phosphoric acid - phosphoric acid

Strong and Weak Acids

weak acids ionize as reversible or weak acids ionize as reversible or equilibrium reactionsequilibrium reactionsCHCH33COOH acetic acid COOH acetic acid

why they ionize less than 100%why they ionize less than 100%

COH

O

CH3

aq-aq3

7%

3 H + COOCH COOHCH

Strong Soluble BasesStrong Soluble Basesbases produce OHbases produce OH-- ions in solution ions in solution

strong soluble bases ionize 100% in strong soluble bases ionize 100% in waterwater

KOH K (aq) + OH (aq)

Ba(OH) Ba (aq) + 2 OH (aq)

+ -

22+ -

Strong Soluble Basesentire list of strong soluble basesentire list of strong soluble bases

LiOH - lithium hydroxideLiOH - lithium hydroxideNaOH - sodium hydroxideNaOH - sodium hydroxideKOH - potassium hydroxideKOH - potassium hydroxideRbOH - rubidium hydroxideRbOH - rubidium hydroxideCsOH - cesium hydroxideCsOH - cesium hydroxideCa(OH)Ca(OH)22 - calcium hydroxide - calcium hydroxide

Sr (OH)Sr (OH)22 - strontium hydroxide - strontium hydroxide

Ba (OH)Ba (OH)22 - barium hydroxide - barium hydroxide

Insoluble Bases

ionic but insoluble in water ionic but insoluble in water

not very basicnot very basicCu(OH)Cu(OH)22 - copper (II) hydroxide - copper (II) hydroxide

Fe(OH)Fe(OH)22 - iron (II) hydroxide - iron (II) hydroxide

Fe(OH)Fe(OH)3 3 - iron (III) hydroxide- iron (III) hydroxide

Zn(OH)Zn(OH)22 - zinc (II) hydroxide - zinc (II) hydroxide

Mg(OH)Mg(OH)22 - magnesium hydroxide - magnesium hydroxide

Weak Bases

covalent compounds that ionize slightly covalent compounds that ionize slightly in waterin water

NHNH33 - ammonia is most common - ammonia is most common

-(aq)aq42g3 OH + NH OH + NH

Solubility Rulesstrong acidsstrong acids

completely water solublecompletely water soluble

strong basesstrong basescompletely water solublecompletely water soluble

soluble ionic saltssoluble ionic saltsFigure 4.3, page 80 of textbookFigure 4.3, page 80 of textbook

Dissociation = pre-formed ions in solid Dissociation = pre-formed ions in solid move apart in solution.move apart in solution.

Ionization = neutral substance forms Ionization = neutral substance forms ions in solution.ions in solution.

AcidAcid = substances that ionizes to = substances that ionizes to form form HH++ in solution in solution (e.g. (e.g. HCl, HNOHCl, HNO33, CH, CH33COCO22HH, , lemon, lime, vitamin C).lemon, lime, vitamin C).

Bases Bases = = substances that substances that react withreact with the Hthe H++ ions formed by acids (e.g. ions formed by acids (e.g. NHNH33, , Drano™, Milk of Magnesia™).Drano™, Milk of Magnesia™).

Acids, Bases, and Salts

Reactions in Aqueous Solutions

molecular equationsmolecular equations all reactants & products in molecular or all reactants & products in molecular or

ionic formionic form

total ionic equationtotal ionic equation ions as they exist in solutionions as they exist in solution

(s)(aq)4(aq)4(s) Cu + ZnSO CuSO + Zn

(s)-2aq4

2aq

-2aq4

2aq(s) Cu +SO+ ZnSO+ Cu+Zn

Reactions in Aqueous Solutions

net ionic equationnet ionic equation shows ions that participate in reaction and removes shows ions that participate in reaction and removes

spectator ionsspectator ions

spectator ions do not participate in the reactionspectator ions do not participate in the reaction

(s)2aq

2aq(s) Cu + ZnCu + Zn

Metathesis reactions involve swapping ions in Metathesis reactions involve swapping ions in solution:solution:

AX + BY AX + BY AY + BX. AY + BX.Metathesis reactions will lead to a change in Metathesis reactions will lead to a change in solution if one of three things occurs:solution if one of three things occurs:

an insoluble solid is formed (precipitate),an insoluble solid is formed (precipitate),

weak or nonelectrolytes are formed, orweak or nonelectrolytes are formed, or

an insoluble gas is formed.an insoluble gas is formed.

Displacement Reactions

Displacement Reactions

Precipitation Reactionsform an insoluble compoundform an insoluble compound

crystalscrystals

molecular equationmolecular equation

(s)3)aq(3aq)(32(aq)23 CaCO +KNO 2 COK + )Ca(NO

Precipitation Reactionsform an insoluble compoundform an insoluble compound

crystalscrystals


total ionic reactiontotal ionic reaction

(s)3)aq(3aq)(32(aq)23 CaCO +KNO 2 COK + )Ca(NO

Precipitation Reactionstotal ionic reactiontotal ionic reaction

s3-

aq3aq

-2aq3aq

-aq3

2aq

CaCO NO 2K 2

COK 2 NO 2 Ca

Precipitation Reactionstotal ionic reactiontotal ionic reaction

net ionic reactionnet ionic reaction

s3-

aq3aq

-2aq3aq

-aq3

2aq

CaCO NO 2K 2

COK 2 NO 2 Ca

Precipitation Reactionsnet ionic reactionnet ionic reaction

(s)3-2aq3

2aq CaCO CO +Ca

Neutralization occurs when a solution of an Neutralization occurs when a solution of an acidacid and a and a basebase are mixed: are mixed:

HCl(HCl(aqaq)) + + NaOH(NaOH(aqaq)) H H22O(O(ll) + NaCl() + NaCl(aqaq))

Notice we form a salt (NaCl) and water.Notice we form a salt (NaCl) and water.

Salt = ionic compound whose cation comes Salt = ionic compound whose cation comes from a base and anion from an acid.from a base and anion from an acid.

Neutralization between acid and metal Neutralization between acid and metal hydroxide produces water and a salt.hydroxide produces water and a salt.


Acid-Base Reactionsacid + base salt + wateracid + base salt + water

recall the acids and bases from beforerecall the acids and bases from before


Acid-Base Reactionsacid + base salt + wateracid + base salt + water

recall the acids and bases from beforerecall the acids and bases from before


total ionic equationtotal ionic equation

)(2 (aq)(aq)(aq) OH + KBr KOH + HBr

Acid-Base Reactionstotal ionic equationtotal ionic equation

net ionic equationnet ionic equation

)(2-aqaq

-aqaq

-aqaq OH + Br+KOH+K+Br+H

Acid-Base Reactionsnet ionic equationnet ionic equation

)(2-aqaq OH OH +H

Acid-Base Reactionsmolecular equationmolecular equation

)(2aq)(23(aq)3(aq)2 OH 2 + )Ca(NOHNO 2 + Ca(OH)

Acid-Base Reactionsmolecular equationmolecular equation

total ionic equationtotal ionic equation

)(2aq)(23(aq)3(aq)2 OH 2 + )Ca(NOHNO 2 + Ca(OH)

Acid-Base Reactionstotal ionic equationtotal ionic equation

net ionic equationnet ionic equation

)(2-

aq32aq

-aq3aq

-aq

2aq OH 2 +NO 2+ CaNO 2+ H 2+OH 2+Ca

Acid-Base Reactionsnet ionic equationnet ionic equation

)(2aq-aq

)(2aq-aq

OH H+OH

betteror

OH 2 H 2+OH 2

Solution = solute dissolved in solvent.Solution = solute dissolved in solvent. Solute: present in smallest amount.Solute: present in smallest amount. Water as solvent = aqueous solutions.Water as solvent = aqueous solutions. Change concentration by using different Change concentration by using different

amounts of solute and solvent.amounts of solute and solvent.Molarity: Moles of solute per liter of Molarity: Moles of solute per liter of

solution.solution. If we know: molarity and liters of If we know: molarity and liters of

solution, we can calculate moles (and solution, we can calculate moles (and mass) of solute.mass) of solute.

Solution Composition

Molarity: Moles of solute per liter of Molarity: Moles of solute per liter of solution.solution.

Solution Composition

Concentration of Solutions solution - one substance dissolved in solution - one substance dissolved in

another, commonly one is a liquidanother, commonly one is a liquid concentration - amount of solute concentration - amount of solute

dissolved in a solventdissolved in a solvent• ““sweet tea”sweet tea”• mixed drinksmixed drinks

units of concentrationunits of concentration

% by mass of solute = mass of solute

mass of solutionmass of solution = mass of solute + mass of solvent

100%

Molarity (Molar Concentration) molarity = mol solute/L of solution = molarity = mol solute/L of solution = MM

Calculate the molarity of a solution that Calculate the molarity of a solution that contains 12.5 g of sulfuric acid in 1.75 L contains 12.5 g of sulfuric acid in 1.75 L of solution.of solution.

Molarity (Molar Concentration) molarity = mol solute/L of solution = molarity = mol solute/L of solution = MM

Calculate the molarity of a solution that Calculate the molarity of a solution that contains 12.5 g of sulfuric acid in 1.75 L contains 12.5 g of sulfuric acid in 1.75 L of solution.of solution.

? mol H SO

L sol'n

12.5 g H SO

L sol'n

1 mol H SO

98.1 g H SO

mol H SO

L M H SO

2 4 2 4 2 4

2 4

2 42 4

175

0 07280 0728

.

..

Molarity (Molar Concentration) Determine the mass of calcium nitrate Determine the mass of calcium nitrate

required to prepare 3.50 L of 0.800 M required to prepare 3.50 L of 0.800 M Ca(NOCa(NO33))2 2 . .

Molarity (Molar Concentration) Determine the mass of calcium nitrate Determine the mass of calcium nitrate

required to prepare 3.50 L of 0.800 M required to prepare 3.50 L of 0.800 M Ca(NOCa(NO33))2 2 . .

? g Ca(NO L 0.800 mol Ca(NO

L164 g Ca(NO

mol Ca(NO g Ca(NO

33

3

33

) .)

)

))

22

2

22

3 50

1459

Dilution of Solutions take a concentrated solution and add water to ittake a concentrated solution and add water to it

• make tea “less sweet”make tea “less sweet” number of moles of solute remains constantnumber of moles of solute remains constant MM11VV11 = M = M22VV22 works because # of moles is works because # of moles is

constantconstant If 10 mL of 12 M HCl is added to enough water If 10 mL of 12 M HCl is added to enough water

to give 100 mL of solution, what is concentration to give 100 mL of solution, what is concentration of solution?of solution?

Dilution of Solutions take a concentrated solution and add water to ittake a concentrated solution and add water to it

• make tea “less sweet”make tea “less sweet” number of moles of solute remains constantnumber of moles of solute remains constant MM11VV11 = M = M22VV22 works because # of moles is constant works because # of moles is constant If 10 mL of 12 M HCl is added to enough water to If 10 mL of 12 M HCl is added to enough water to

give 100 mL of solution, what is concentration of give 100 mL of solution, what is concentration of solution?solution?

(10 mL)(12 M) = M(10 mL)(12 M) = M22(100 mL)(100 mL)

MM2 2 = 1.2 M HCl= 1.2 M HCl

Dilution of Solutions What volume of 18.0 M sulfuric acid is What volume of 18.0 M sulfuric acid is

required to make 2.50 L of a 2.40 M required to make 2.50 L of a 2.40 M sulfuric acid solution?sulfuric acid solution?

Dilution of Solutions What volume of 18.0 M sulfuric acid is What volume of 18.0 M sulfuric acid is

required to make 2.50 L of a 2.40 M required to make 2.50 L of a 2.40 M sulfuric acid solution?sulfuric acid solution?

M x V M x V VM x V

M

V2.50 L x 2.40 M

18.0 M0.333 L or 333 mL

1 1 2 2 12 2

1

1

Stoichiometry with Solutions

There are two different types of units: •laboratory units (macroscopic units: measure in lab);•chemical units (microscopic units: relate to moles).

Always convert the laboratory units into chemical units first.

•Grams are converted to moles using molar mass.•Volume or molarity are converted into moles using M = mol/L.

Use the stoichiometric coefficients to move between reactants and product.

Stoichiometry with Solutions

Stoichiometry with Solutions What volume of 0.500 M BaClWhat volume of 0.500 M BaCl22 is is

required to completely react with 4.32 g required to completely react with 4.32 g of Naof Na22SOSO44??

L0.0608 BaClmol 0.500

BaCl L1

SONa mol 1

BaClmol 1

SONa g 142

SONa mol 1 SOgNa 4.32 BaCl L?

NaCl 2 + BaSO BaCl+ SONa

2

2

42

2

42

42422

4242

Stoichiometry with Solutions What volume of 0.200 M NaOH will react with What volume of 0.200 M NaOH will react with

50.0 mL 0f 0.200 M aluminum nitrate? What 50.0 mL 0f 0.200 M aluminum nitrate? What mass of aluminum hydroxide precipitates?mass of aluminum hydroxide precipitates?

Al(NOAl(NO33))33 + 3 NaOH + 3 NaOH Al(OH) Al(OH)33 + 3 NaNO + 3 NaNO33

Stoichiometry with Solutions What volume of 0.200 M NaOH will react with What volume of 0.200 M NaOH will react with

50.0 mL 0f 0.200 M aluminum nitrate? What 50.0 mL 0f 0.200 M aluminum nitrate? What mass of aluminum hydroxide precipitates?mass of aluminum hydroxide precipitates?

Al(NOAl(NO33))33 + 3 NaOH + 3 NaOH Al(OH) Al(OH)33 + 3 NaNO + 3 NaNO33

? mL NaOH = 50.0 mL Al(NO ) sol' n

0.200 mol Al(NO ) sol' n

1 L Al(NO ) sol' n

3 mol NaOH1 mol Al(NO )

L NaOH0.200 mol NaOH

150 mL NaOH sol' n

3 3

3 3

3 3 3 3

1

Stoichiometry in Solution

What mass of Al(OH)What mass of Al(OH)33 precipitates in (a)? precipitates in (a)?

Stoichiometry in Solution

What mass of Al(OH)What mass of Al(OH)33 precipitates in (a)? precipitates in (a)?

? g Al(OH) 50.0 mL Al(NO ) sol'n

0.200 mol Al(NO )

L Al(NO ) sol'n

1 mol Al(OH)

1 mol Al(NO )

g Al(OH)

1mol Al(OH)

g Al(OH)

3 3 3

3 3

3 3

3

3 3

3

3

3

1

78 0

0 780

.

.

Titrations

Titrations

Suppose we know the molarity of a NaOH solution and we want to find the molarity of an HCl solution.We know:

molarity of NaOH, volume of HCl.What do we want?

Molarity of HCl.What do we do?

Take a known volume of the HCl solution, measure the mL of NaOH required to react completely with the HCl.

Titrations

What do we get?Volume of NaOH. We know molarity of the NaOH, we can calculate moles of NaOH.

Next step?We also know HCl + NaOH NaCl + H2O. Therefore, we know moles of HCl.

Can we finish?Knowing mol(HCl) and volume of HCl (20.0 mL above), we can calculate the molarity.

Titrations What is the molarity of a KOH solution if What is the molarity of a KOH solution if

38.7 mL of KOH solution is required to 38.7 mL of KOH solution is required to react with 43.2 mL of 0.223 M HCl?react with 43.2 mL of 0.223 M HCl?

KOH + HCl KCl + H O

43.2 mL 0.223 M HCl = 9.63 mmol HCl

9.63 mmol HCl1 mol KOH1 mol HCl

mmol KOH

9.63 mmol KOH

38.7 mL KOH M KOH

2

9 63

0 249

.

.

Titrations What is the molarity of a barium What is the molarity of a barium

hydroxide solution if 44.1 mL of 0.103 hydroxide solution if 44.1 mL of 0.103 MM HCl is required to react with 38.3 mL of HCl is required to react with 38.3 mL of the Ba(OH)the Ba(OH)22 solution? solution?



23-

23-

3-

222

Ba(OH) mol 2.27x10

HCl mol 2

Ba(OH) mol 1HCl mol 1054.4

HCl mol 4.54x10 = HCl) 1L

mol 0.103)(

1000

1HCl)( mL 1(44.

OH 2 + BaCl HCl 2 + Ba(OH)

x

mL

L



22

23-

222

Ba(OH) M 0.0593 Ba(OH) mL 0.0383

Ba(OH) mol 2.27x10

OH 2 + BaCl HCl 2 + Ba(OH)

Oxidation Number Rules The oxidation number of any free, uncombined The oxidation number of any free, uncombined

element is zero.element is zero. The oxidation number of an element in a The oxidation number of an element in a

simple (monatomic) ion is the charge on the simple (monatomic) ion is the charge on the ion.ion.

In the formula for In the formula for anyany compound, the sum of compound, the sum of the oxidation numbers of all elements in the the oxidation numbers of all elements in the compound is zero. In a polyatomic ion, the compound is zero. In a polyatomic ion, the sum of the oxidation numbers of the sum of the oxidation numbers of the constituent elements is equal to the charge on constituent elements is equal to the charge on the ion.the ion.

Oxidation Number Rules

Hydrogen, H, in combined form, has Hydrogen, H, in combined form, has the oxidation number +1, the oxidation number +1, usuallyusually..

Oxygen, O, in combined form, has Oxygen, O, in combined form, has the oxidation number -2, the oxidation number -2, usuallyusually..

Oxidation Numbers assign oxidation numbers to each assign oxidation numbers to each

element in these compoundselement in these compoundsNaNONaNO33 KK22Sn(OH)Sn(OH)66 HH33POPO44



+1 +5 -2+1 +5 -2



+1 +5 -2+1 +5 -2 +1 +4 -2 +1 +1 +4 -2 +1



+1 +5 -2+1 +5 -2 +1 +4 -2 +1 +1 +4 -2 +1 +1 +5 -2 +1 +5 -2


element in these polyatomic ionselement in these polyatomic ionsSOSO33

2-2- HCOHCO33-- CrCr22OO77

2-2-




2-2-

+4 -2+4 -2




2-2-

+4 -2+4 -2 +1+4 -2+1+4 -2




2-2-

+4 -2+4 -2 +1+4 -2+1+4 -2 +6 -2 +6 -2

Redox Reactions oxidation - loss of electronsoxidation - loss of electrons

• oxidation number increasesoxidation number increases reduction - gain of electronsreduction - gain of electrons

• oxidation number decreases or reduces!oxidation number decreases or reduces! oxidizing agents - chemical species oxidizing agents - chemical species

that gain electrons and oxidize some that gain electrons and oxidize some other speciesother species• electron thieves electron thieves • they are reduced they are reduced

Redox Reactions

reducing agents - chemical species reducing agents - chemical species that lose electrons and reduce some that lose electrons and reduce some other speciesother species• victims of electron thieves victims of electron thieves • they are oxidizedthey are oxidized

How do we balance redox reactions?How do we balance redox reactions?

Balancing redox reactions.Balancing redox reactions.• Half-Reaction MethodHalf-Reaction Method

Balancing Redox ReactionsBalancing Redox Reactions

Balancing redox reactions by half reaction Balancing redox reactions by half reaction method rules:method rules:

Write the unbalanced reactionWrite the unbalanced reaction Break into 2 half reactions -Break into 2 half reactions -

• 1 for oxidation1 for oxidation• 1 for reduction1 for reduction

Mass balance each half reaction by adding Mass balance each half reaction by adding appropriate stoichiometric coefficentsappropriate stoichiometric coefficents• in acidic solutions we can add Hin acidic solutions we can add H++ or H or H22OO

• in basic solutions we can add OHin basic solutions we can add OH-- or H or H22OO

Half Reaction MethodHalf Reaction Method

Charge balance the half reactions by Charge balance the half reactions by adding appropriate numbers of adding appropriate numbers of electronselectrons

Multiply each half reaction by a number Multiply each half reaction by a number to make the number of electrons added to make the number of electrons added equal to the number of electrons equal to the number of electrons consumedconsumed

Add the two half reactionsAdd the two half reactions Eliminate any common terms Eliminate any common terms


Example: Tin (II) ions are oxidized to tin Example: Tin (II) ions are oxidized to tin (IV) by bromine. Use the half reaction (IV) by bromine. Use the half reaction method to write and balance the net ionic method to write and balance the net ionic equation.equation.

reaction starting BrSnBrSn -+42

+2



reaction halfoxidation e2Sn Sn

reaction starting BrSnBrSn-+4+2

-+42

+2



reaction halfreduction Br 2e2Br

reaction halfoxidation e2Sn Sn

reaction starting BrSnBrSn

--2

-+4+2

-+42

+2



Sn Br Sn Br starting reaction

Sn Sn e oxidation half reaction

Br e 2 Br reduction half reaction

Sn Br Sn Br balanced reaction

2+2

4+ -

2+ 4+ -

2- -

2+2

4+ -

2

2

2


Example: Dichromate ions oxidize iron (II) ions to Example: Dichromate ions oxidize iron (II) ions to iron (III) ions and are reduced to chromium (III) iron (III) ions and are reduced to chromium (III) ions in acidic solution. Write and balance the net ions in acidic solution. Write and balance the net ionic equation for the reaction.ionic equation for the reaction.

reaction starting FeCrFeOCr +3+3+2272



reaction halfoxidation 1e+ FeFe

reaction starting FeCrFeOCr-+3+2

+3+3+2272



red. OH 7Cr 2 e 6H 14OCr

ox. 1e+ FeFe

rxnstart FeCrFeOCr

2+3-+2

72

-+3+2

+3+3+2272




ox. 1e+ FeFe 6

rxnstart FeCrFeOCr

2+3-+2

72

-+3+2

+3+3+2272



OH 7Cr 2Fe 6H 14OCrFe 6


ox. 1e+ FeFe 6

rxnstart FeCrFeOCr

2+3+3+2

72+2

2+3-+2

72

-+3+2

+3+3+2272


Example: In basic solution hydrogen Example: In basic solution hydrogen peroxide oxidizes chromite ions, peroxide oxidizes chromite ions, Cr(OH)Cr(OH)44

--, to chromate ions, CrO, to chromate ions, CrO442-2-. .

Write and balance the net ionic Write and balance the net ionic equation for this reaction.equation for this reaction.


OH8CrO 2OH 3OH2Cr(OH) 2

6OH+OH8CrO 2OH 3OH8Cr(OH) 2

OH2e2OH3

3e+OH4CrOOH4Cr(OH)2

solution) (basic CrOOHCr(OH)

22

422-

4

-2

2422

-4

--22

-2

24

-4

24224


Example: When chlorine is bubbled Example: When chlorine is bubbled into basic solution, it forms chlorate into basic solution, it forms chlorate ions and chloride ions. Write and ions and chloride ions. Write and balance the net ionic equation.balance the net ionic equation.


Cl 5+ OH 3ClO OH 6Cl 3

Cl 10+ OH 6ClO 2OH 12Cl 6

Cl 2e 2Cl 5

10e + OH 6ClO 2OH 12Cl 1

solution) (basic ClClOCl

23-

2

23-

2

-2

-23

-2

32


Synthesis Question

Nylon is made by the reaction of Nylon is made by the reaction of hexamethylene diammine hexamethylene diammine

with adipic acidwith adipic acidCH2

CH2CH2

CH2CH2

CH2NH2

NH2

C

OH

O CH2

CH

2

CH2

CH

2

C

OH

O

Synthesis Question in a 1 to 1 mole ratio. The structure of in a 1 to 1 mole ratio. The structure of

nylon is:nylon is:

where the value of n is typically where the value of n is typically 450,000. On a daily basis, a DuPont 450,000. On a daily basis, a DuPont factory makes 1.5 million pounds of factory makes 1.5 million pounds of nylon. How many pounds of nylon. How many pounds of hexamethylene diamine and adipic acid hexamethylene diamine and adipic acid must they have available in the plant must they have available in the plant each day?each day?

CNH

O

CH

2

CH2

CH2

CH

2

CH2

CH

2

C

O

CH

2

CH2

CH

2

NH ** n

Group Activity

Manganese dioxide, potassium hydroxide Manganese dioxide, potassium hydroxide and oxygen react in the following fashion:and oxygen react in the following fashion:

A mixture of 272.9 g of MnOA mixture of 272.9 g of MnO22, 26.6 L of , 26.6 L of 0.250 M KOH, and 41.92 g of O0.250 M KOH, and 41.92 g of O22 is allowed is allowed to react as shown above. After the to react as shown above. After the reaction is finished, 347.6 g of Kreaction is finished, 347.6 g of K22MnOMnO44 is is separated from the reaction mixture. separated from the reaction mixture. What is the per cent yield of this reaction?What is the per cent yield of this reaction?

OH 2 KMnO 4 O 3 + KOH 4 + MnO 4 2422

CHAPTER 4 Reactions in Aqueous Solutions. Aqueous Solutions aqueous solutions -solute dissolved in...

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Transcript of CHAPTER 4 Reactions in Aqueous Solutions. Aqueous Solutions aqueous solutions -solute dissolved in...