AMSAT CAMSAT CHEMHEM 1H T 1H TOPICOPIC#15#15AACIDCID/B/BASESASES N NOTESOTES

TABLE OF CONTENTS

1. Ionization 2. Properties of Acids/Bases 3. Acid/Base Theories 4. Aqueous Solutions and the Concept of pH 5. Determining pH and Titrations

IONIZATION SECTION#1

● Ionizationo Ions form from solute molecules by the action of the solvent.

HCl H2O→ H+(aq) + Cl-(aq) HCl(g) is a molecular compound but ionizes when bubbled into water forming the

acid, hydrochloric acid.o Water

Self-ionizes H2O(l) + H2O(l) → H3O+(aq) + OH-(aq)

o The action of one water molecule on another water molecule causes the transfer of a H from one to the other creating the hydronium ion, H3O+

(aq).o Strong electrolytes

Full ionization of molecule into ions or a solution containing ions from a soluble ionic compound

Strong acids, strong bases, all group 1 and ammonium compounds.o Conduct electricity well

o Weak electrolytes No/partial ionization of a molecular compound or a solution containing an insoluble ionic

compound. Weak acids, weak bases, molecular compounds, insoluble ionic compounds

(Fe3(PO4)2)o Do not conduct electricity or conduct poorly

PROPERTIES OF ACIDS/BASES SECTION #2

● Acids (distinct class of compounds)o Acids are ionized by water (polar compound and polar solvent)o Acids start as molecular compounds (start with nonmetal, H) which react with water

ionization

HCl(g) + H2O(l) → H3O+(aq) + Cl-(aq)● After reacting with water, produces the hydronium ion, H3O+(aq), and an anion.

o Strong acids (SA) HCl(aq), HBr(aq), HI(aq), HNO3(aq), H2SO4(aq), HClO4(aq), and HClO3(aq) Strong electrolytes (allow electricity to pass through)

● Fully ionize into ions in a solutiono 100% ionization

HCl(aq) → H+(aq) + Cl-(aq)

1Home

0% 100%o Weak Acids (WA)

CH3COOH(aq), H2CO3(aq), HNO2(aq), HF(aq), H3PO4(aq), etc. Weak electrolytes

● Partially ionize 10%ionization

o HF(aq) + H2O(l) ↔ H3O+(aq) + F-(aq) 1M 0 0 0.9M 0.1M 0.1M

5% ionization

o CH3COOH(aq) + H2O(l) ↔ H3O+(aq) + CH3COO-(aq) 1M (5%) 0 0 0.95M 0.05M 0.05M

o How to produce an acid (definition an acid is an aqueous solution).

A gaseous molecular compound is bubble through water

● Produces a binary acido HCl(g), HF(g),

HBr(g), etc. HCl(aq) ,

HF(aq), HBr(aq), etco Naming

Anion – chloride, remove –ide, add ic, add prefix hydro and end with acid.Names of Binary Acids

Formula Acid NameHF(aq) hydrofluoric acidHCl(aq) hydrochloric acidHBr(aq) hydrobromic acidHI(aq) hydroiodic acid

H2S(aq) hydrosulfuric acid

Nonmetal oxide (acidic anhydride) reacts with water● Oxyacids

o P4O10(s) + 6H2O(l) → 4H3PO4(aq) Phosphoric acid

o N2O5(s) + H2O(l) → 2HNO3(aq) Nitric acid

o CO2(g) + H2O(l) → H2CO3(aq) Carbonic acid

o SO2(g) + H2O(l) → H2SO3(aq) Sulfurous acid

o SO3(g) + H2O(l) → H2SO4(aq) Sulfuric acid

● Namingo Take anion – if it ends in –ate, add –ic and acid

NO3- → nitrate, remove the –ate add –ic and acid to get nitric acid

NO2- → nitrite, remove the –ite add –ous and acid to get nitrous

acid

2

Names of Common Oxyacids and OxyanionsFormula Acid Name Anion

CH3COOH(aq) acetic acid CH3COO-, acetateH2CO3(aq) carbonic acid CO3

2-, carbonateHIO3(aq) iodic acid IO3

-, iodateHClO(aq) hypochlorous acid ClO-, hypochloriteHClO2(aq) chlorous acid ClO2

-, chloriteHClO3(aq) chloric acid ClO3

-, chlorateHClO4(aq) perchloric acid ClO4

-, perchlorateHNO2(aq) nitrous acid NO2

-, nitriteHNO3(aq) nitric acid NO3

-, nitrateH3PO3(aq) phosphorous acid PO3

3-, phosphiteH3PO4(aq) phosphoric acid PO4

3-, phosphateH2SO3(aq) sulfurous acid SO3

2-, sulfiteH2SO4(aq) sulfuric acid SO4

2-, sulfate

o Specific Properties(1) Sour taste (do not EVER taste an acid in the lab)(2) pH < 7(3) React with bases to produce a salt and water(4) Change the color of an acid/base indicator

● An indicator is usually a weak acid(5) Reacts with an active metal to produce H2(g)

● 2HCl(aq) + Zn(s) → H2(g) + ZnCl2(aq)(6) Can be an electrolyte

● SA (strong acids) are strong electrolytes● WA (weak acid) are weak electrolytes

(7) Turns blue litmus to red (acid:red)o Industrial acids

Sulfuric acid (H2SO4)● Most common industrial chemical in the WORLD

o Metallurgy, fertilizers, paper, dyes, detergents; effective dehydrating agent (attracts water); Dehydrates sugars

Nitric acid (HNO3)● Explosives, rubber, plastics, dyes, and pharmaceuticals

Phosphoric acid (H3PO4)● Fertilizers, dilute can be used as a flavoring agent

Hydrochloric acid (HCl)● “Pickling” of iron and steel

o Removes surface impurities Acetic acid (HC2H3O3/CH3COOH)

● Vinegar (4-8% acetic acid), plasticsCommon Aqueous Acids

Strong acids Weak AcidsH2SO4 + H2O → H3O+ + HSO4

- HSO4- + H2O ↔ H3O+ + SO4

2-

HClO4 + H2O → H3O+ + ClO4- H3PO4 + H2O ↔ H3O+ + H2PO4

-

HCl + H2O → H3O+ + Cl- HF + H2O ↔ H3O+ + F-

HNO3 + H2O → H3O+ + NO3- CH3COOH + H2O ↔ H3O+ + CH3COO-

HBr + H2O → H3O+ +Br- H2CO3 + H2O ↔ H3O+ + HCO3-

3

Home

HI + H2O → H3O+ + I- HCN + H2O ↔ H3O+ + CN-

HCO3- + H2O ↔ H3O+ + CO3

2-

● Baseso Bases dissociate in watero Most come from solid ionic compounds

NaOH(s) H2O→ Na+(aq) + OH-(aq)● Produce hydroxide ions and a cation

o Strong Bases (SB) Group I and some of Group II hydroxides (cations plus hydroxide)

● LiOH(s), NaOH(s), KOH(s), RbOH(s), CsOH(s), Ca(OH)2(s), Sr(OH)2(s), and Ba(OH)2(aq)

o CaO (quick lime) is included because it reacts with water to become Ca(OH)2(aq): CaO(s) + H2O(l) → Ca(OH)2(aq)

Strong electrolytes● Fully dissociate into cations and hydroxide ions

o 100% dissociation NaOH(s) H2O→ Na+(aq) + OH-(aq)

0% 100% o Weak Bases (WB)

A metal hydroxide other than Group I or Sr(OH)2, Ca(OH)2, and Ba(OH)2

NH3(ammonia) Weak electrolytes

● Do not fully dissociateo Mg(OH)2(s) ↔ Mg2+(aq) + 2OH-(aq)

≈ 100% ≈ 0% (1x10-8%)o How to make a basic (or alkaline) solution

Dissolve a solid hydroxide in water● Ca(OH)2(s) H2O→ Ca2+(aq) + 2OH-(aq)

React an active metal oxide (basic anhydride) with water● Na2O(s) + H2O(l) → 2Na+(aq) + 2OH-(aq)● CaO(s) + H2O(l) → Ca2+(aq) + 2OH-(aq)● BaO(s) + H2O(l) →Ba2+(aq) + 2OH-(aq)

Naming● Use ionic nomenclature

o NaOH(aq) – a solution of sodium hydroxide● Specific name

o NH3 – ammoniao CH3NH2 – methyl amineo NaOH(aq) – lye (common name)

o Specific Properties(1) Taste bitter(2) pH > 7(3) React with acids to produce water and a salt(4) Change the color of an acid/base indicator

4

Home

(5) Dilute solutions feel slippery(6) Can be an electrolyte (SB – strong electrolyte)(7) Turns litmus to blue (base:blue)

Common Aqueous BasesStrong Bases Weak Bases

Ca(OH)2 → Ca2+ + 2OH- NH3 + H2O ↔ NH4+ + OH-

Sr(OH)2 → Sr2+ + 2OH- C6H5NH2* + H2O ↔ C6H5NH3

+ + OH-

Ba(OH)2 → Ba2+ + 2OH-

NaOH → Na+ + OH-

KOH → K+ + OH-

RbOH → Rb+ + OH- * analine, a substance to make dyes is a weak base because of the N.CsOH → Cs+ + OH-

ACID/BASE THEORIES SECTION#3

● Arrhenius Acids/Baseso Acids

Directly contribute H+ to solution● Increases the [H+] in solution ([x] means concentration of x)● All of the strong acids● Most of the weak acids

o HCN(aq), HF(aq), CH3COOH(aq), etc.● Must have an acidic H

o An acidic H can be donated directly from a polar molecule as it dissolves (ionizes) in water to become an acid

o Bases Directly contributes OH- to solution

● Increases the [OH-] in solution● All strong bases● Very few weak bases

o Exception Ammonia can be considered an Arrhenius base because of its

strong attraction for the H in water NH3(g) + H2O(l) → NH4

+(aq) + OH-(aq)● Brønsted-Lowry Acids/Bases

o Acid Molecule/ion that is a proton donor (H+) After the molecule/ion has donated an H+, it becomes the conjugate base of the acid

o Base Molecule/ion that is a proton acceptor (H+) After the molecule/ion has accepted an H+, it becomes the conjugate acid of the base.

● Conjugate acid-base pairo An acid and its conjugate base or a base and its conjugate acid

Example:

● HCl + NH3 → NH4+ + Cl-

A B CA CBo The HCl donates a H+ to the NH3 molecule

5

Home

HCl is the BL acid and BL NH3 is the base HCl donates an H+ to become Cl- NH3 accepts the H+ to become NH4

+ Cl- is the conjugate base of HCl NH4

+ is the conjugate acid of NH3 Conjugate acid-base pairs

HCl and Cl-

NH3 and NH4+

o Sample Problem – 15.1 Conjugate Acid-Base PairsIdentify acid, base, conjugate acid, conjugate base, the conjugate acid-base pairs and draw an arrow to represent the transfer of H+.

(1) H3PO4(aq) + H2O(l) → H2PO4-(aq) + H3O+(aq)

(2) CO32-(aq) + H2O(l) → HCO3

-(aq) + OH-(aq)(3) NH4

+(aq) + H2O(l) → NH3(aq) + H3O+(aq)(4) HClO2(aq) + OH-(aq) → ClO2

-(aq) + H2O(l)o Polyprotic acids

Monoprotic acid● Donates one H+ (HCl, HNO3, etc.)

Polyprotic acids● Donates more than one H+ (H2SO4, H2SO3, H3PO4, H3PO3, etc.)● Conjugate base of an acid always has one less hydrogen than the acid

o H2SO4 + H2O(l) → HSO4- + H3O+

o HSO4- + H2O ↔ SO4

2- + H3O+ Notice: first ionization is strong (→), second is weak (↔),

equilibrium This means H2SO4 is a much stronger acid than HSO4

- Even though HSO4

- is the conjugate base of H2SO4 it still is a stronger acid than water, so it acts like an acid when it reacts with water.

o Sample Problem 15.2 – Ionization of a Polyprotic AcidWrite the three equations for the ionization of the weak acid, H3PO4(aq).

o Strength of Conjugate Acids and Bases Strong acids produce weak conjugate bases

● HCl(aq) + H2O(l) → H3O+(aq) + Cl-(aq) SA B A WB

o Cl- is a very weak base and H2O is a stronger baseo The stronger the acid the weaker the conjugate base.

● HClO4(aq) + H2O(l) → H3O+(aq) + ClO4-(aq)

stronger acid stronger base weaker acid weaker baseo Hydronium ion is too weak of an acid to compete with perchloric acid in

the donation of a protono H2O competes more strongly for the H+ from HClO4

● CH3COOH(aq) + H2O(l) ← H3O+(aq) + CH3COO-(aq) weaker acid weaker base stronger acid stronger base

o Due to the products being a stronger acid and base than the reactants, most of the acid does not ionize.

Confirms acetic acid is a weak acid with 5% ionization Proton transfer reactions favor the production of a weaker acid and weaker base

6

Monoprotic vs. Polyprotic

Home

Relative Strengths of Acids and Conjugate BasesConjugate Acid Formula Conjugate Base Formula

chloric acid HClO3 chlorate ion ClO3-

hydrobromic acid HBr bromide ion Br-

hydroiodic acid HI iodide ion I-

hydrochoric HCl chloride ion Cl-

nitric acid HNO3 nitrate ion NO3-

perchloric acid HClO4 perchlorate ion ClO4-

sulfuric acid H2SO4 hydrogen sulfate ion SO42-

hydronium ion H3O+ water H2Ochlorous acid HClO2 chlorite ion ClO2

-

hydrogen sulfate ion HSO4- sulfate ion SO4

2-

phosphoric acid H3PO4 dihydrogen phosphate ion H2PO4-

hydrofluoric acid HF fluoride ion F-

acetic acid CH3COOH acetate ion CH3COO-

carbonic acid H2CO3 hydrogen carbonate ion HCO3-

hydrosulfuric acid H2S hydrosulfide ion HS-

dihydrogen phosphate ion H2PO4- hydrogen phosphate ion HPO4

2-

hypochlorous acid HClO hypochlorite ion ClO-

ammonium ion NH4+ ammonia NH3

hydrogen carbonate ion HCO3- carbonate ion CO3

2-

hydrogen phosphate ion HPO42- phosphate ion PO4

3-

water H2O hydroxide ion OH-

ammonia NH3 amide ion NH2-

hydrogen H2 hydride ion H-

o Sample Problem 15.3 – Strengths of Conjugate Acids and Bases(a) Order the following bases from weakest to strongest: Cl-, H2O, F-, and CO3

2-.(b) Order the following acids from weakest to strongest: NH4

+, HPO42-, HCO3

-, and H2PO4-

o Amphoteric Compounds A species that can react as either a base or an acid

● Watero HCl(aq) + H2O(l) → H3O+(aq) + Cl-(aq)

As a base (proton accepter)o NH3(g) + H2O(l) ↔ NH4

+(aq) + OH-(aq) As an acid (proton donor)

● Hydrogen sulfate iono HSO4

-(aq) + H2O(l) → H3O+(aq) + SO42-(aq)

o HSO4-(aq) + HClO3(aq) → H2SO4(aq) + ClO3

-(aq) -OH in a Molecule

7

Str

ong

Aci

ds Very W

eak Bases

Incr

easi

ng A

cid

Stre

ngth Increasing Base Strength

Home

● Molecular compounds containing –OH can be acidic or basico –OH in an acid is called a hydroxyl group

Covalently bondedo For a compound to be acidic, a water molecule must be able to separate

the H for the –OH The more polar the O-H bond is the easier it is for water to “take”

the H The smaller, more electronegative nonmetal atoms in the upper

right of the periodic table form compounds with acidic hydroxyl groups.

They make the O-H bond more polaro The figure below shows the electron dot formulas

for the four oxyacids of chlorine. Notice all of the oxygen atoms are bonded to the chlorine and the hydrogen is bonded to an oxygen.

● A series of similar acids increases in acidic strength as oxygens are added to the anion

o HClO < HClO2 < HClO3 < HClO4

As more oxygens are added it pulls the electrons in the O-H bond closer to the O thus making it easier for water to pull the H from the O

● Behavior of a compound is affected by the number of O atoms bonded to the atom connected to the –OH group.

● The larger the number of O atoms, the more acidic the compound is likely to be.● The highly EN oxygen atoms draw electron density away from the –OH group

and making the O-H bond more polar.o For example:

basic amphoteric acidicCr(OH)2 vs. Cr(OH)3 vs. H2CrO4

chromium (II) chromium(III) chromic acid hydroxide hydroxide

o Sample Problem 15.4 – Strength of OxyacidsOrder the following acids weakest to strongest: HIO3(aq), HIO2(aq), HIO(aq), and HIO4(aq).

● Neutralization Reactionso A reaction between a base and an acid

Sodium bicarbonate and tartaric acid found in baking powder

● Do not react in their solid state● React and produce CO2 when added to water to

form a solutiono Gives baked products their fluffy texture

o SA-SB Neutralization Complete conversion into products, water and a salt

HCl(aq) + NaOH(aq) → H2O(l) + NaCl(aq)HCl(aq) → H3O+(aq) + Cl-(aq)NaOH(aq) → Na+(aq) + OH-(aq)

H3O+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) → Na+(aq) + Cl-(aq) + 2H2O(l)

8

Home

Net: H3O+(aq) + OH-(aq) → 2H2O(l)A reaction between hydronium and hydroxide ions

o Acid Rain Gas produce from an industrial process (NO, NO2, CO2, SO2, and SO3)

● Combine with H2O in the air: SO2(g) + H2O(l) → H2SO3(aq) Acid rain reacts with marble, CaCO3 (ancient sea shells from aquatic animals)

● CaCO3(s) + H2SO3(aq) → Ca2+(aq) + CO2(g) + 2H2O(l)● Lewis Acids/Bases

o Acids An atom, ion, or molecule that accepts an e- pair to form a covalent bond

● H+(aq) + :NH3(aq) → [H-NH3+](aq) or NH4

+(aq) Does not require an H to be available

● Ag+(aq) + 2:NH3(aq) → [H3N-Ag-NH3]+(aq) or [Ag(NH3)2]+ (aq)o Many transition metal cations are Lewis acids

o Base Atom, ion, or molecule that donates an e- pair to form a covalent bond

● BF3(aq) + :F-(aq) → BF4-(aq)

o B has only six valence e-‘s in BF3 so it can add another pair of electrons BF3 is a Lewis acid reacting with F-

In the above reactions, NH3 and F- are Lewis baseso Lewis acid/base reaction

Formation of one/more covalent bonds between an e--pair donor and an e--pair acceptor.

AQUEOUS SOLUTIONS AND THE CONCEPT OF PH SECTION#4

● Self Ionization of Pure Water (Hydronium and Hydroxide Ions)o In pure water, water molecules react with each other.

H2O(l) + H2O(l) → H3O+(aq) + OH-(aq); Produces the hydronium ion and hydroxide ion. Water acts like an acid and a base (amphoteric)

o [H3O+] will equal the concentration of hydroxide, [OH-] in pure water [H3O+] = [OH-] = 1.0x10-7 M

o The equilibrium constant (or equilibrium product) for water, Kw. Kw = [H3O+] x [OH-] = 1.0x10-14 or = [H3O+][OH-] = 1.0x10-14

● Usually no units with an equilibrium constant, just remember concentrations have a unit of M(molarity)

● [H3O+] = _Kw_ and [OH-] = _Kw_

[OH-] [H3O+] Acidic solution

● [H3O+] > 1.0x10-7 and [OH-] < 1.0x10-7 o [H3O+] > [OH-] and [H3O+] x [OH-] = 1.0x10-14

Basic solution● [H3O+] < 1.0x10-7 and [OH-] > 1.0x10-7

o [H3O+] < [OH-] and [H3O+] x [OH-] = 1.0x10-14 Neutral solution

● [H3O+] = 1.0x10-7 and [OH-] = 1.0x10-7 and [H3O+] x [OH-] = 1.0x10-14 o Sample Problem 16.1 – Calculating [H3O+] and [OH-]

9

Acid-Base SystemsType Acid Base

Arrhenius H+ or H3O+ producer OH- producerBrønsted-Lowry proton (H+) donor proton (H+) acceptor

Lewis e-- pair acceptor e-- pair donor

Home

A 1.0x10-4M solution of HNO3(aq) has been prepared for a laboratory experiment. Calculate the [H3O+] and [OH-]. Ans: 1.0x10-4M, and 1.0x10-10M

Practice (1) Determine the [H3O+] and [OH-] in a solution that is 1x10-4M HCl.

Ans: [H3O+] = 1x10-4M, [OH-] = 1x10-10M(2) Determine the [H3O+] and [OH-] in a solution that is 3.0x10-2M NaOH.

Ans: [H3O+] = 3.3x10-13M, [OH-] = 3.0x10-2M(3) Determine the [H3O+] and [OH-] in a solution that is 1x10-4M Ca(OH)2.

Ans: [H3O+] = 5.0x10-11M, [OH-] = 2.0x10-4M The pH Scale

pH 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

[H3O+] 1 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-14

Increasing acidity neutral Increasing basicity pH < 7 pH = 7 pH > 7

● Comes from the French word, pouvoir hydrogene, meaning “hydrogen power.”● The negative logarithm of the hydronium concentration

o pH = -log[H3O+] or –log[H+]● Scale goes from 0-14

o 0 to 7 acidic solution [H3O+] > [OH-]

o 7 neutral solution (pH of pure water) [H3O+] = [OH-]

o 7 to 14 basic solution [H3O+] < [OH-]

● The opposite of the pH scale is the pOH scaleo The hydroxide powero pOH = -log[OH-]

● pH + pOH = 14o acidic: pH < 7 and pOH > 7

[H3O+] > 1.0x10-7M and [OH-] < 1.0x10-7Mo neutral: pH = 7 = pOH

[H3O+] = 1.0x10-7M and [OH-] = 1.0x10-7Mo basic: pH >7 and pOH < 7

[H3O+] < 1.0x10-7M and [OH-] > 1.0x10-7M Relationship of [H3O+] to [OH-]

[H3O+], [OH-], pH, and pOH of SolutionsSolution General Condition At 25oCNeutral [H3O+] = [OH-]

pH = pOH[H3O+] = [OH-] = 1x10-7M

pH = pOH = 7Acidic [H3O+] > [OH-] [H3O+] > 1x10-7M

10

Home

pH < pOH [OH-] < 1x10-7MpH < 7 and pOH > 7

Basic [H3O+] < [OH-]pH > pOH

[H3O+] < 1x10-7M[OH-] > 1x10-7M

pH > 7 and pOH < 7

Concentrations and Kw

● Determining [H3O+] from pHo pH = -log[H3O+]

[H3O+] = 10-pH [OH-] = Kw/[H3O+]

● Determining [OH-] from pOHo pOH = -log[OH-]

[OH-] = 10-pOH [H3O+] = Kw/[OH-]

o Sample Problem 16.2 – pH from [H3O+] or [OH-] without a CalculatorWhat is the pH of a 1.0x10-3M NaOH solution? Ans: pH = 11.00

Practice Determine the pH of the following solutions:

(a) 1x10-3M HCl Ans: 3.0 (b) 1.0x10-2M KOH Ans: 12.00

o Sample Problem 16.3 – pH from [H3O+] or [OH-] with a CalculatorWhat is the pH of a solution if the [H3O+] is 3.4x10-5M? Ans: 4.47

Practice (1) Determine the pH of a 2.5x10-6M HNO3 solution. Ans: 5.60(2) Determine the pH of a 2.0x10-2M Sr(OH)2 solution. Ans: 12.60

o Sample Problem 16.4 – Calculating [H3O+] or [OH-] from pHDetermine the hydronium ion concentration of an aqueous solution with a pH of 4.0.

Ans: [H3O+] = 1x10-

4M o Sample Problem 16.6 – Calculating [H3O+] or [OH-] from pH

The pH of a solution is measured and determined to be 7.52.(a) What is the hydronium ion concentration? Ans: 3.0x10-8M H3O+ (b) What is the hydroxide concentration? Ans: 3.3x10-7M OH- (c) Is the solution acidic or basic? Ans: basic

Practice (1) The pH of a solution is determined to be 1.50. Calculate the [H3O+] and [OH-]. Is the

solution acidic, basic, or neutral? Ans: [H3O+] = 3.2x10-2M, [OH-] = 3.2x10-13M

pH Values for a Specified [H3O+] Approximate pH Range of Common Materials

11

Home

DETERMINING PH AND TITRATIONS SECTION#5

● Indicators and pH meterso Acid-base Indicators

Compounds whose colors are sensitive to pH Weak acid or weak base molecule HIn ↔ H+ + In-

● In- symbol for the anion part of the indicator In an acidic solution

● The indicator exists as HIn In a basic solution

● The indicator exists as an H+ and In-

In basic solutionHIn ↔ H+ + In-

In acidic solution Transition Interval

● pH range of color change in an indicator

Universal indicator componentsIndicator Low pH color Transition pH range High pH color

Thymol blue (first transition) Red 1.2 – 2.8 YellowMethyl red Red 4.4 – 6.2 YellowBromothymol blue Yellow 6.0 – 7.6 BlueThymol blue (second transition) Yellow 8.0 – 9.6 BluePhenolphthalein Colorless   8.3 – 10.0 Fuchsia

Color Ranges of Various Indicators Used in Titrations

12

Home

o pH paper paper treated with acid-base indicator

● Paper changes color due to concentration of [H3O+] and [OH-]● Gives a general idea of pH

o pH Meters Determines the pH of a solution by measuring the voltage the solution can transmit

● All solutions have some ability to transmit electricity● Gives an accurate measurement of pH

● Titrationo Controlled addition of a solution of known molarity to an unknown amount of a solution until all

of the unknown has reactedo Equivalence point (stoichiometric point)

The point where the two solutions used in a titration have chemically equivalent amounts

For acid and bases● [H3O+] = [OH-] @ the equivalence point● Strong acid/strong base titration

o [H3O+] = [OH-] = 1.0x10-7M pH = 7

o End point

13

Home

Point where the color of the indicator changes coloro Titration curve

A graph of the pH versus amount of acid/base(mL) added S-shaped with a vertical line in the middle

● Represents the pH change around the equivalence pointo Very sudden pH changeo End point (color change of indicator) occurs along the vertical line, too.

SA/SB Titration● Curve starts with a pH of 0-1● Ends with a pH of 12-14● Equivalence point is at pH of 7

WA/SB● Curve starts with a pH of 2-6● Ends with a pH of 12-14● Equivalence point is at pH > 7

Titration Curve for a SA and a SB Titration Curve for a WA and SB

SB/SA Titration● Curve starts with a pH of 12-14● Ends with a pH of 0-1● Equivalence point is at pH of 7

WB/SA● Curve starts with a pH of 8-11● Ends with a pH of 0-1● Equivalence point is at pH < 7

Performing a Titration Part #1

14

Home

Home

15Home

Performing a Titration Part#2

Transition Ranges for Some Indicators

16Home

● Molarity and Titrationo Standard solution

Precisely known concentrationo Primary standard

Highly purified solid compound used to check the concentration of the known solution in a titration

o NaVa = NbVb (Acid/base Titration Equation) Na the molarity of the acid * by the number of hydrogens in the acid (Na = Macid x V) Va the volume of the acid Nb the molarity of the base * by the number of hydroxides in the base (Nb = Mbase x #OH) Vb the volume of the base

o Sample Problem 16.6 – TitrationsIn a titration, 27.4mL of 0.0154 M Ba(OH)2 is added to a 20.0mL sample of HCl solution of unknown concentration. What is the M of the acid solution?

Ans: 4.22x10-

2M HCl Practice - Titrations

(1) A 15.5mL sample of 0.215 M KOH solution required 21.2mL of aqueous acetic acid solution in a titration experiment. Calculate the molarity of the acetic acid solution.

Ans: 0.157 M (2) By titration, 17.6mL of aqueous H2SO4 neutralize 27.4mL of 0.0165M LiOH

solution. What was the molarity of the aqueous acid solution? Ans: 0.0128M

17

Home