chapter 19 notes - weebly · 2019. 8. 31. · chapter 19 notes 1 chapter 19 acids, bases, and salts...

Chapter 19 Notes

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CHAPTER 19Acids, Bases, and Salts

19.1 AcidBase TheoriesACIDS

• tart or sour taste• Electrolytes• Strong acids are corrosive

• indicators will change color• Blue litmus paper turns pink• react with metals to form H2• react with OH to form water and a salt.• Feel like water.

Acid Facts... Definitions for Acids/Bases

• Dilute: small amount of solute• Concentrated: large amount of solute• Indicator: changes color to show the

presence of acids or bases• Corrosive: eat or wear away

Common Acids in Food• Citric Acid: lemons, oranges• Malic Acid: apples• Acetic Acid: Vinegar, Catsup

(Ketchup)• Lactic Acid: sour milk• Phosphoric Acid: soda pop• Tartaric Acid: wine

Chapter 19 Notes

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Common Reactions with Acids Rule #1 for Naming Acids• ide• hydro(stem)ic acid• Ex. Hydrochloric acid

HCl: Hydrogen chloride

H2S: Dihydrogen sulfide

HBr: Hydrogen bromide

HF: Hydrogen fluoride

• ite• (stem)ous acid• Ex. Sulfurous acid H2SO3

Rule #2 for Naming Acids

H2SO3: Dihydrogen sulfite

H3PO3: Trihydrogen phosphite

HNO2: Hydrogen nitrite

• ate• (stem)ic acid• Ex. Nitric Acid HNO3

Rule #3 for Naming Acids

Chapter 19 Notes

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H2SO4: Dihydrogen sulfate

H3PO4: Trihydrogen phosphate

HNO3: Hydrogen nitrate

H2CO3: Dihydrogen carbonate

Sulfuric Acid• Fertilizer• Used to produce paint, dye, and metal• Battery Acid• Very strong and causes severe burns

Nitric Acid• Used in making explosives• Used in making plastics, rubber, dyes, and drugs• Causes serious burns

Hydrochloric Acid• Produced in the stomach• Used to remover impurities from the surface of metal

Phosphoric Acid• Flavors beverages• Used to make detergents and ceramics• If dilute, it is not toxic.

BASES• react with acids to form water and a salt• bitter taste• Strong bases are corrosive• Group 1A metals form stronger bases than Group 2A metals.

K+ + OH

Na+ + OH

Mg2+ + OH

Ca2+ +OH

Chapter 19 Notes

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• feel slippery• Alkaline solutions.• electrolytes• indicators change color• Red litmus paper blue

Base Facts... Common Bases• Household Ammonia • Cleaners, Window Cleaner• Lye and Drain Cleaner• Sodium Hydroxide• Milk of Magnesia (Laxative)• Antacids (Tums, Rolaids, etc.)

Arrhenius Acids and Bases• ACIDS: compounds containing

hydrogen that ionize to yield hydrogen ions in aqueous solution

• BASES: compounds that ionize to yield hydroxide ions in aqueous solution

H+ or H3O+

OH

BronstedLowry Acids and Bases• ACID: hydrogenion donor• BASE: hydrogenion acceptor• An acid and a base react to form a conjugate acid and a conjugate base. When dissolved

IonizationH+ NO3

Arrhenius Acids• Monoprotic: HNO31 ionizable hydrogen• Diprotic:H2SO42 ionizable hydrogen• Triprotic: H3PO43 ionizable hydrogen

Chapter 19 Notes

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• Conjugate Acid: forms when a base gains a hydrogen

• Conjugate Base: forms when an acid donates a hydrogen

• Conjugate AcidBase Pair

• HCl + H2O à H3O+ + Cl• NH3 + H2O à NH4+ + OH

• Conjugate Acid: forms when a base gains a hydrogen• Conjugate Base: forms when an acid donates a hydrogen• Conjugate AcidBase Pair

> AcidConugate Base> BaseConjugate Acid


HCl + H2O à H3O+ + Cl

NH3 + H2O à NH4+ + OH

Amphoteric• Substances that either act as a base or an acid.• Water is the best example.


Lewis Acids & BasesLewis Acids: accept an electron pair

Lewis Bases: donate an electron pair

This expands Acid/Base definitions, by allowing us to classify acids and bases in the absence of H+, H3O+, and OH.

19.2 Hydrogen Ions and Acidity

• An acid is a compound that produces hydrogen ions when dissolved in water• General formula: HX

Chapter 19 Notes

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• The reaction in which two water molecules react to give ions is the selfionization of water.

• The selfionization of water occurs to a very small extent.

H2O ↔ H+ + OH

• If Hydrogen ions are released, it causes a shift that will lower hydroxide ions. HCl àH+ + Cl• If Hydroxide ions are released, it causes a shift that will lower hydrogen ions. NaOH àNa+ + OH

Water is at EquilibriumRemember your shifting rules!!!

Hydrogen Ions and Acidity• A water molecule that loses a hydrogen ion becomes a negatively charged hydroxide ion (OH)

NH3 + H2O à NH4+ + OH

• A water molecule that gains a hydrogen ion becomes a positively charged hydronium ion (H3O+)

HCl + H2O à H3O+ + Cl

Hydrogen Ions and Acidity

• Ionproduct constant for water• 1 x 10 14

ACID• H+ greater than OH

BASE• OH greater than H+

• [OH] increases, then [H+] decreases!

• [OH] decreases, then [H+] increases!• Kw = [H+] x [OH] = 1.0 x 1014 mol/L2

Chapter 19 Notes

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Kw = [H+] x [OH] = 1.0 x 1014 mol/L2

[H+] = 1.0 x 1014 mol/L2 ÷ [OH] [OH] = 1.0 x 1014 mol/L2 ÷ [H+]

• Finding the [OH] of a solution.

• The [H+] is 1.0 x 10 –5 mol/L.• Kw = [H+] x [OH]

• Acid = [H+] greater than 1.0 x 10 –7• Base = [H+] less than 1.0 x 107• Neutral = [H+] equal to 1.0 x 107(Examples, see page 598.)

The pH Scale• pH = 0> Many H+ ions> Few or no OH ions

• pH = 14> Many OH ions> Few or no H+ ions

• pH = 7> Number of “H+ ions” and “OH ions” are equal

What is a logarithm?log 100 = 2 (This means 102 = 100)

log 50 = 1.699 (This means 101.699 = 50)

log 0.5 = .301 ( This means 10.301 = 0.5)

Calculating Logarithms

• 5.6

• 3.2

• 0.00056

• 2.5 x 106

Chapter 19 Notes

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Calculating Antilogarithms

• 3.26

• 6.9

• 0.56

• 4.8

The pH Concept• The pH of a solution is the negative logarithm of the [H+] concentration• pH = log (H+)• The [H+] concentration is the antilogarithm of the negative pH.• [H+] = antilog ( pH)

Calculating pH from [H+] concentration

• Always find the [H+] concentration first

What is the pH for the following?1. [H+] = 1.0 x 1010 mol/L2. [H+] = .0000001 M3. [OH] = 1.0 x 1012 mol/L (Two ways)4. [OH] = .0001 M5. [OH] = 1.0 x 107 6. [H+] = 6.73 x 10 11 M

Calculating [H+] concentration from pH

• Take antilog of negative pH.

What is the [H+] for the following pH?1. 4.02. 6.03. 12.04. 8.05. 7.06. 11.65

Measuring pH

• Indicators: use color• Usually a piece of paper• Litmus paper does not give the strength.• pH meters: accurate and fast measurements

H+ Concentration OH Concentration pH pOH

6.23 x 10 2

9.4

11.5

There will be a chart just like this on the Homework Quiz.

3.67 x 10 4

Chapter 19 Notes

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19.3 STRENGTHS OF ACIDS AND BASES

• Strong acids completely ionize and weak acids only partly ionize.• Strong acids are strong electrolytes and weak acids are weak electrolytes

• Chart page 605

What does strong mean?• Strong acids and bases ionize more than weak acids and bases.• 8.0 M phosphoric acid is not as dangerous as 1.0 M sulfuric acid.

• Concentration and ionization are two different things.• Ionization determines strength• Concentration is used to compare the same acids with a different molarity.

Complete vs. Partial IonizationStrong Acids have maximum ionization and have no reverse reaction.

• HCl + H2O à H3O+ + Cl

Weak Acids have partial ionization and stay at equilibrium

• HC2H3O2(aq) + H2O(l) H3O+(aq) + C2H3O2 (aq)Maximum Ionization

Strong AcidVery Little Ionization

Weak Acid

The conjugate base is pulling so strong on the H+ that it allows the reaction to reverse and stay at equilibrium

Water is pulling so strong on the H+ that the conjugate base cannot attract it enough to reverse

Acid Strength & BronstedLowry ModelWhat attracts the H+ ion more, the base or the conjugate base?

HX(aq) + H2O(l) à H3O+(aq) + X(aq)

HX(aq) + H2O(l) H3O+(aq) + X(aq)

acid base Conugate Acid

Conugate Base

acid base Conugate Acid

Conugate Base

Which is the strongest acid?

• [H+] = 1.0 x 105 M • [OH] = 1.0 x 1012 M

• [H+] = 1.0 x 1011 M

• [OH] = 1.0 x 104 M

Hint: always use pH to determine strength!!!

Chapter 19 Notes

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Strong BASES• react with acids to form water and a salt• Metallic hydroxides are strong bases• Strong bases are corrosive• Group 1A metals form stronger bases than Group 2A metals.

K+ + OH

Na+ + OH

Mg2+ + OH

Ca2+ +OH

The conjugate base is pulling so strong on the H+ that it allows the reaction to reverse and stay at equilibrium

What attracts the H+ ion more, the base or the conjugate base?

NH3(aq) + H2O(l) NH4+(aq) + OH(aq)

CH3NH2(aq) + H2O(l) CH3NH3+(aq) + OH(aq)

acidbase Conugate Acid

Conugate Base

acidbase Conugate Acid

Conugate Base

Weak Bases

Which is the strongest base?

• [H+] = 1.0 x 103 M • [OH] = 1.0 x 107 M

• [H+] = 1.0 x 1013 M

• [OH] = 1.0 x 1011 M

Hint: always use pH to determine strength!!!Strong Acids Weak Acids

HClO4 H3PO4

HCl HF

HNO3 HC2H3O2

H2SO4 HCN

H2S

H2CO3

What is the Hydrogen ion concentration if 3.5 x 10-3 M acid ionizes at 13.0%?

What is the pH & pOH?

What is the Hydroxide ion concentration if 4.7 x 10-2 M base ionizes at 8.0%?

What is the pH & pOH?

Chapter 19 Notes

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19.4 NEUTRALIZATION REACTIONS

• A reaction in which an acid and a base react in aqueous solution to produce a salt and water.

H2SO4 + 2NaOH 2H2O + Na2SO4

Neutralization Reactions

1. Determine the number of moles in the known solution.

2. Using stoichiometry, determine the moles of unknown solution needed.

3. Answer the question using what you know about the unknown solution.

n

VM

Easy way to solve for the missing component of the unknown solution.

• Neutralization reactions are also considered salt production reactions.

• After neutralizing the acid and base, heating the solution will produce salt.

AcidBase Reactions: produce salt and water

HCl + KOH

H2SO4 + Ca(OH)2

H3PO4 + Al(OH)3

Steps in aNeutralization Reactions• Titration• Equivalence Point• Standard Solution• End Point• Titration curves

TITRATIONThe addition of a known amount of solution of known concentration to determine the concentration of another solution.

H2SO4 NaOHM : 2.0M M :

V: V: 20mL

n: n:

Chapter 19 Notes

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4.0M

0.5L

HCl + NaOH H2O + NaClSTANDARD

NaOH

HCl HCl NaOHM : 4.0M M :

V: V: 0.5L

n: n:

Performing a Titration• Standard Solution• The solution of known concentrationRemember: concentration = molarity• ex.) .50M HCl

Equivalence Point• The number of moles of hydrogen ions must

equal the number of moles of hydroxide ions.• Use stoichiometry!• Mathematically neutral!!!!

• Sometimes, the indicator does not change at the equivalence point.

End Point• The point at which the indicator changes color.

• Not always equal to equivalence pointSometimes, the pH change is so drastic that it takes the indicator extra time to change.

• AKA...point of neutralization.

Phenophtalein• Universal indicator for acidbase neutralization reactions.

• Pink in a base• Colorless in an acid

Example #1How many moles of H2SO4 would you require to neutralize 0.50 mol of NaOH? (Regular stoichiometry)

• Write a balanced equation.

• Find the ratio of H2SO4 to NaOH.• Solve the problem.


Chapter 19 Notes

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Neutralization Reactions

1. Determine the number of moles in the known solution.

2. Using stoichiometry, determine the moles of unknown solution needed.

3. Answer the question using what you know about the unknown solution.

n

VM

Easy way to solve for the missing component of the unknown solution.

Example #2 AHow much 1.0M H2SO4 is needed to neutralize 1.0L of 2.0M NaOH? H2SO4 NaOH

M : M :

V: V:

n: n:


Example #2 BHow much 2.0M H2SO4 is needed to neutralize 1.0L of 2.0M NaOH? H2SO4 NaOH

M : M :

V: V:

n: n:


Example #2 CHow much 5.0M H2SO4 is needed to neutralize 1.0L of 2.0M NaOH? H2SO4 NaOH

M : M :

V: V:

n: n:


Example #3 – AIf 1.0Lof H2SO4 neutralizes 1.0L of 2.0M NaOH, what is the concentration of H 2SO4?

H2SO4 NaOHM : M:

V: V:

n: n:


Example #3 – BIf 2.0Lof H2SO4 neutralizes 1.0L of 2.0M NaOH, what is the concentration of H2SO4?

H2SO4 NaOH

M : M :

V: V:

n: n:


Chapter 19 Notes

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Example #3 – CIf 4.0Lof H2SO4 neutralizes 1.0L of 2.0M NaOH, what is the concentration of H2SO4?

H2SO4 NaOHM : M :

V: V:

n: n:


Example #4

A 25mL solution of H2SO4 is neutralized by 18 mL of 1.0 M NaOH using phenolphthalein as an indicator. What is the concentration of the H2SO4 solution?

H2SO4 NaOHM : M :

V: V:

n: n:


BronstedLowry Acids and Bases• ACID: hydrogenion donor• BASE: hydrogenion acceptor• An acid and a base react to form a

conjugate acid and a conjugate base.

• Conjugate Acid: forms when a base gains a hydrogen

• Conjugate Base: forms when an acid donates a hydrogen

• Conjugate AcidBase Pair


Buffers• A solution of weak acid and conjugate base or weak base and conjugate acid.• Able to resist drastic changes in pH better than pure water• Why is some aspirin buffered?

Buffer Capacity

The point at which a buffer can no longer resist change in pH.Dependent on the amount of acid or base that is added.

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chapter 19 notes - weebly · 2019. 8. 31. · chapter 19 notes 1 chapter 19 acids, bases, and salts...

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