Acids, Bases, and SaltsAcids, Bases, and SaltsCh 15 & 16Ch 15 & 16

Introduction to Acids and Bases.asx

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Properties of Acids Ch 15.1Properties of Acids Ch 15.1

Acid Property #1.Acid Property #1. The word acid The word acid comes from the Latin word comes from the Latin word acereacere, which , which means "sour." All acids taste sour. means "sour." All acids taste sour.

Acid Property #2.Acid Property #2. In 1663, Robert In 1663, Robert Boyle wrote that acids would make a Boyle wrote that acids would make a blue vegetable dye called "litmus" turn blue vegetable dye called "litmus" turn red. red.

Acid Property #3.Acid Property #3. Acids destroy the Acids destroy the chemical properties of bases. chemical properties of bases.

Properties of acids and bases.asx

Acid Property #4.Acid Property #4. Acids conduct an Acids conduct an electric current. electric current.

Acid Property #5.Acid Property #5. Upon chemically Upon chemically reacting with an reacting with an activeactive metal, acids will metal, acids will evolve hydrogen gas (Hevolve hydrogen gas (H22). ).

Properties of BasesProperties of Bases

Base Property #1.Base Property #1. The word "base" has The word "base" has a more complex history and its name is a more complex history and its name is not related to taste. All bases taste bitter.not related to taste. All bases taste bitter.

Base Property #2.Base Property #2. Bases are Bases are substances which will restore the original substances which will restore the original blue color of litmus after having been blue color of litmus after having been reddened by an acid. reddened by an acid.

Base Property #3.Base Property #3. Bases destroy the Bases destroy the chemical properties of acids. chemical properties of acids.

Base Property #4.Base Property #4. Bases conduct an Bases conduct an electric current. electric current.

Base Property #5.Base Property #5. Bases feel Bases feel slippery, sometimes people say soapy. slippery, sometimes people say soapy. This is because they dissolve the fatty This is because they dissolve the fatty acids and oils from your skin and this acids and oils from your skin and this cuts down on the friction between your cuts down on the friction between your fingers as you rub them together. fingers as you rub them together.

The Acid Base TheoryThe Acid Base Theory Ch 15.2Ch 15.2

The three main theories regarding The three main theories regarding acids and bases are:acids and bases are:

1. Arrhenius1. Arrhenius

2. Brønsted-Lowry2. Brønsted-Lowry

3. 3. LewisLewis

Svante Arrhenius (1859-1927)Svante Arrhenius (1859-1927)

Arrhenius Acids.asx

Svante ArrheniusSvante Arrhenius Swedish chemist (1859-1927) Swedish chemist (1859-1927)

- Nobel prize winner in - Nobel prize winner in chemistry (1903)chemistry (1903)

one of the first chemists to one of the first chemists to explain the chemical theory of explain the chemical theory of the behavior of acids and the behavior of acids and basesbases

1. Arrhenius Definition1. Arrhenius Definition

AcidsAcids produce hydrogen ions (H produce hydrogen ions (H1+1+) in ) in aqueous solution.aqueous solution.

BasesBases produce hydroxide ions (OH produce hydroxide ions (OH1-1-) ) when dissolved in water.when dissolved in water.

Limited to aqueous solutions.Limited to aqueous solutions. Only one kind of base (hydroxides)Only one kind of base (hydroxides) NHNH33 (ammonia) could be an (ammonia) could be an

Arrhenius base? NHArrhenius base? NH44OH?OH?

Polyprotic AcidsPolyprotic Acids

Some compounds have more than 1 Some compounds have more than 1 ionizable hydrogen.ionizable hydrogen.

HNOHNO3 3 nitric acid - monoproticnitric acid - monoprotic HH22SOSO44 sulfuric acid - diprotic - 2 H sulfuric acid - diprotic - 2 H++

HH33POPO44 phosphoric acid - triprotic - 3 phosphoric acid - triprotic - 3 HH++

Having more than one ionizable Having more than one ionizable hydrogen does not mean stronger!hydrogen does not mean stronger!

Johannes Bronsted / Thomas Johannes Bronsted / Thomas LowryLowry (1879-1947) (1874- (1879-1947) (1874-1936)1936)

Bronsted Acids.asx

2. Brønsted-Lowry Definitions2. Brønsted-Lowry Definitions

Broader definition than ArrheniusBroader definition than Arrhenius Acid is hydrogen-ion donor (HAcid is hydrogen-ion donor (H+ + or proton); or proton);

base is hydrogen-ion acceptor.base is hydrogen-ion acceptor. Acids and bases always come in pairs.Acids and bases always come in pairs. HCl is an acid.HCl is an acid.

When it dissolves in water, it gives it’s When it dissolves in water, it gives it’s proton to water.proton to water.

HCl(g) + HHCl(g) + H22O(l) O(l) HH33OO++ + Cl + Cl--

Water is a base; makes hydronium ion.Water is a base; makes hydronium ion.

Acids and bases come in pairs...Acids and bases come in pairs...

Conjugate acid-bases.asx

Acids and bases come in Acids and bases come in pairs...pairs...

A A conjugate baseconjugate base is the is the remainder of the original acid, remainder of the original acid, after it donates it’s hydrogen ionafter it donates it’s hydrogen ion

A A conjugate acidconjugate acid is the particle is the particle formed when the original base formed when the original base gains a hydrogen iongains a hydrogen ion

Indicators are weak acids or Indicators are weak acids or bases that have a different color bases that have a different color from their original acid and basefrom their original acid and base

Acids and bases come in Acids and bases come in pairs...pairs...

General equation is: General equation is: HA(aq) + HHA(aq) + H22O(l) O(l) H H33OO++(aq) + A(aq) + A--

(aq)(aq) Acid + Base Acid + Base Conjugate acid +Conjugate acid +

Conjugate baseConjugate base NHNH33 + H + H22O NHO NH44

1+1+ + OH + OH1-1-

base acid c.a. c.b.base acid c.a. c.b. HCl + HHCl + H22O HO H33OO1+1+ + Cl+ Cl1-1-

acid base c.a. c.b. acid base c.a. c.b. Amphoteric - acts as acid or baseAmphoteric - acts as acid or base

Bases and Conjugate AcidBases and Conjugate Acid

BaseBase NameNameConjugatConjugate acide acid NameName

CHCH33OOOO--

Acetate ionAcetate ion CHCH33COOHCOOH Acetic acidAcetic acid

NHNH33 AmmoniaAmmonia NHNH44++ AmmoniumAmmonium

HH22POPO44-- Dihydrogen Dihydrogen

phosphate ionphosphate ionHH33POPO44 Phosphoric Phosphoric

acidacid

HSOHSO44-- Hydrogen sulfate Hydrogen sulfate

ionionHH22SOSO44 Sulfuric acidSulfuric acid

OHOH-- Hydroxide ionHydroxide ion HH2200 waterwater

NONO33-- Nitrate ionNitrate ion HNOHNO33 Nitric acidNitric acid

HH22OO waterwater HH3300++ Hydronium Hydronium ionion

StrengthStrength

Strong acids and bases are strong Strong acids and bases are strong electrolyteselectrolytes They fall apart (ionize) completely.They fall apart (ionize) completely. Weak acids don’t completely ionize.Weak acids don’t completely ionize.

StrengthStrength different from different from concentrationconcentration Strong-forms many ions when dissolvedStrong-forms many ions when dissolved Mg(OH)Mg(OH)22 is a strong base- it falls is a strong base- it falls

completely apart when dissolved. completely apart when dissolved. But, not much dissolves- not But, not much dissolves- not

concentratedconcentrated

Strong and weak acids.asx

What about bases?What about bases? Strong bases dissociate completely.Strong bases dissociate completely. Weak bases only slightly ionize in Weak bases only slightly ionize in

waterwater

Strength vs. ConcentrationStrength vs. Concentration The words The words concentratedconcentrated and and dilutedilute

tell how much of an acid or base is tell how much of an acid or base is dissolved in solution - refers to the dissolved in solution - refers to the number of moles of acid or base in number of moles of acid or base in a given volumea given volume

The words The words strongstrong and and weakweak refer to refer to the extent of ionization of an acid the extent of ionization of an acid or baseor base

Is a concentrated weak acid Is a concentrated weak acid possible?possible?

Strong AcidsStrong Acids

*HNO*HNO33 - nitric acid - nitric acid *HCl - hydrochloric *HCl - hydrochloric

acid acid*H*H22SOSO44- sulfuric acid - sulfuric acid *HClO*HClO44 - perchloric - perchloric

acid acid *HBr - hydrobromic *HBr - hydrobromic

acid acid*HI - hydroiodic acid*HI - hydroiodic acid

Strong BasesStrong Bases

*LiOH - lithium hydroxide*LiOH - lithium hydroxide*NaOH - sodium hydroxide*NaOH - sodium hydroxide*KOH - potassium hydroxide*KOH - potassium hydroxide*RbOH - rubidium hydroxide*RbOH - rubidium hydroxide*CsOH - cesium hydroxide*CsOH - cesium hydroxide*Mg(OH)*Mg(OH)22 - magnesium hydroxide - magnesium hydroxide*Ca(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

Self-Ionization of WaterSelf-Ionization of Water

H2O + H2O H3O+ + OH-

KKww – Ionization Constant for Water – Ionization Constant for Water

Kw = (1 x 10-7)(1 x 10-7) = 1 x 10-14

In pure water at 25 C:

[H3O+] = 1 x 10-7 mol/L

[OH-] = 1 x 10-7 mol/L

Kw is a constant at 25 C:

Kw = [H3O+][OH-]

pH ScalepH Scale

The pH scale is a measure of The pH scale is a measure of hydronium ion (Hhydronium ion (H33OO++) concentration.) concentration.

Hydronium ion concentration Hydronium ion concentration indicates acidity. indicates acidity.

The higher the HThe higher the H33OO++, the higher the , the higher the acidity.acidity.

pH scale in nature.asx

pH Lab InstructionspH Lab Instructions

Copy down the chart below on a Copy down the chart below on a separate sheet of paper. 10 Samplesseparate sheet of paper. 10 Samples

SAMPLE # pH Acid Base Guess Identity

Calculating pH, pOHCalculating pH, pOH

pH = -log (H3O+)

pOH = -log (OH-)

Relationship between pH and Relationship between pH and pOHpOH pH + pOH = 14

Finding [HFinding [H33OO++], [OH], [OH--] from pH, pOH] from pH, pOH

[H3O+] = 10-pH

[OH-] = 10-pOH

pH scale.asx

pH and pOHpH and pOH

See Packet See Packet

Calculator FunctionsCalculator Functions

See Book page 488See Book page 488

H+, OH-, and pHH+, OH-, and pH

pH pH ScaleScale

Measuring pH with wide-range Measuring pH with wide-range paperpaper

Narrow-Range pH PaperNarrow-Range pH Paper

pH pH Indicators Indicators and theirand theirrangesranges

ACID-BASE EquilibriaACID-BASE Equilibria

KKaa =Acid- Ionization Constant- =Acid- Ionization Constant- KKbb =Base Ionization Constant =Base Ionization Constant Constant meaning the point at which Constant meaning the point at which

equilibria is reached.equilibria is reached. Weak Acid- Small constant value Weak Acid- Small constant value

because of small dissociation.because of small dissociation. Strong Acid- Large Constant value Strong Acid- Large Constant value

because of large dissociation.because of large dissociation.

ACID-BASE EQULIBRIA ACID-BASE EQULIBRIA CONT:CONT:

Steps to Acid- Base Equlibria Steps to Acid- Base Equlibria problem.problem.

1. Write out acid/ base equation-1. Write out acid/ base equation- HA + HHA + H22O O H H33OO++ + A + A--

2. Write out constant expresssion.2. Write out constant expresssion. KKb/ab/a =[H=[H33OO++ ] [A ] [A--]]

[HA[HA--]]

ACID BASE STEPS:ACID BASE STEPS:

Step 3: Remember : Concentration of Step 3: Remember : Concentration of HH33OO++ ion and the Conjugate base will ion and the Conjugate base will have the same concentration values.have the same concentration values.

KKaa = = (X) (X)(X) (X)

[conc][conc]

Step 4. Plug in values and solve.Step 4. Plug in values and solve.

Ammonia is a weak base. If the initial Ammonia is a weak base. If the initial concentration of ammonia is .150M and the concentration of ammonia is .150M and the equilibrium concentration of OHequilibrium concentration of OH-- is 1.6 x 10 is 1.6 x 10-3-3, , calculate Kcalculate Kbb for ammonia? for ammonia? Step 1. Equation- NHStep 1. Equation- NH33 + H + H22O -> NHO -> NH44

+ OH+ OH--

Step 2: Apply KStep 2: Apply Kbb expression- products expression- products over reactants.over reactants.

Step 3:plug in and solveStep 3:plug in and solve Answer: 1.7 X 10Answer: 1.7 X 10-5-5

2.6 mol of a weak acid is added to 1.0 L of 2.6 mol of a weak acid is added to 1.0 L of water. At equilibrium the concentration of water. At equilibrium the concentration of HH33OO++ is .34M What is the K is .34M What is the Kaa for the acid? for the acid?

5.1 e-25.1 e-2

What is the pH of 1.0 X 10What is the pH of 1.0 X 10-3 -3 M M NaOH solution?NaOH solution?

1111