Acids bases & saltsAcids bases & salts

ObjectivesObjectives

State the Bronsted-Lowry definition of State the Bronsted-Lowry definition of acids and basesacids and basesIdentify the common physical and Identify the common physical and chemical properties of acids and baseschemical properties of acids and basesExplain what dissociation constants Explain what dissociation constants indicate about an acid or baseindicate about an acid or baseUse experimental data to calculate a Use experimental data to calculate a dissociation constantdissociation constant

Properties of acids/basesProperties of acids/bases

TasteTaste – acid comes from latin meaning – acid comes from latin meaning sour or tart/bases are bitter – soap sour or tart/bases are bitter – soap TouchTouch most dilute acids feel like water most dilute acids feel like water although they sting on broken skin bases although they sting on broken skin bases feel smooth, soothing and slippery except feel smooth, soothing and slippery except in your eyes (soap)in your eyes (soap)ReactionsReactions with metal acids react bases with metal acids react bases do not reactdo not react

Properties continuedProperties continued

Electrical conductivityElectrical conductivity water is poor – water is poor – HCl is good, NaOH is good both are HCl is good, NaOH is good both are electrolyteselectrolytesIndicatorsIndicators turn color – acid turns litmus turn color – acid turns litmus paper from blue to red base turns from red paper from blue to red base turns from red to blueto blueNeutralization reaction between an acid Neutralization reaction between an acid and a base get salt and water (double and a base get salt and water (double replacement)replacement)

Arrhenius definitionArrhenius definition

An acid is a substance that dissociates in An acid is a substance that dissociates in water to produce hydrogen ions.water to produce hydrogen ions.A base is a substance that dissociates in A base is a substance that dissociates in water to produce hydroxide ionswater to produce hydroxide ionsA salt is an ionic compound formed from A salt is an ionic compound formed from any cation other that Hany cation other that H++ and any anion and any anion other than OHother than OH-- or O or O-2-2

Arrhenius continuedArrhenius continued

Acids react with metals to produce HAcids react with metals to produce H22 gas gas

Mg +2HMg +2H++ -> Mg -> Mg+2+2 + H + H22

oxidation reduction reactionoxidation reduction reaction

Bronsted – Lowry definitionsBronsted – Lowry definitions

An acid is any substance that can donate An acid is any substance that can donate HH++ ions ionsA base is any substance that can accept A base is any substance that can accept HH++ ions a Bronsted-Lowry acid is a proton ions a Bronsted-Lowry acid is a proton donor and a base is a proton acceptordonor and a base is a proton acceptor

Hydronium IonHydronium Ion

H+ is strongly attracted to the electrons of H+ is strongly attracted to the electrons of surrounding water molecules surrounding water molecules HH++ + H + H22O -> HO -> H33OO++

More correct HCl + HMore correct HCl + H22O -> HO -> H33OO+++ Cl+ Cl--

In this case HCl is the Bronsted-Lowry acid In this case HCl is the Bronsted-Lowry acid and water is the baseand water is the baseWe still describe a solution of HCl as We still describe a solution of HCl as acidic!acidic!

NHNH33 + H + H22O -> NHO -> NH44++ + OH + OH--

Ammonia is the HAmmonia is the H++ acceptor acceptor water is the Hwater is the H++ donor (acid) donor (acid)

Amphoteric a substance that Amphoteric a substance that can act as either an acid or a can act as either an acid or a

basebase

Conjugate Acid-Base PairsConjugate Acid-Base Pairs

NHNH33 + H + H22O O NH NH44++ + OH + OH--

In 1 direction water is the acid in the reverse In 1 direction water is the acid in the reverse reaction it is the base.reaction it is the base.These cmpds become conjugate acids and These cmpds become conjugate acids and conjugate bases when HCl loses an H+ ion to conjugate bases when HCl loses an H+ ion to become its conjugate base Clbecome its conjugate base Cl- - when the when the conjugate base of water is the hydroxide ion OHconjugate base of water is the hydroxide ion OH--

When ammonia gains HWhen ammonia gains H++ to become its to become its conjugate acid NHconjugate acid NH44

++ and the conjugate acid of and the conjugate acid of OHOH-- is H is H22O O

Conjugate pairsConjugate pairs

A pair of compounds that differ by only A pair of compounds that differ by only one Hone H++ ion such as H ion such as H22O and OHO and OH-- or NH or NH33 and NHand NH44

++ are called conjugate acid base are called conjugate acid base pairspairsNHNH33 + H + H22O O NH NH44 ++ + OH + OH--

Base acid conj. Acid conj. baseBase acid conj. Acid conj. base

Determining the strengths of acids Determining the strengths of acids and basesand bases

A strong acid HCl readily transfers A strong acid HCl readily transfers hydrogen ions to water to form Hhydrogen ions to water to form H33OO++

If you place 1M of HCl in 1 liter of water If you place 1M of HCl in 1 liter of water you would form 1 M Hyou would form 1 M H33OO++ ions and 1 M Cl ions and 1 M Cl-- ionsions

weak acidsweak acidsA weak acid does not readily transfer H+ A weak acid does not readily transfer H+ ionsions1 mole of acetic acid in 1 liter of water only 1 mole of acetic acid in 1 liter of water only .4% of the acetic acid molecules would .4% of the acetic acid molecules would form Hform H33OO++ and C and C22HH33OO22

--. Which means that . Which means that 99.6% of the acetic acid molecules do not 99.6% of the acetic acid molecules do not dissociate.dissociate.

To show a strong acid from a weak To show a strong acid from a weak acid use arrowsacid use arrows

HCl + HHCl + H22O O H H33OO++ + Cl + Cl--

HCHC22HH33OO22 + H + H22O <-> HO <-> H33OO++ + C + C22HH33OO22--

Strong and Weak BasesStrong and Weak Bases

The most widely used commercial base is The most widely used commercial base is CaO. When CaO is dissolved in water the CaO. When CaO is dissolved in water the OO-2-2 ions react completely with H ions react completely with H22O to form O to form OHOH-- ions. ions.OO-2-2 + H + H22O O 2OH 2OH- - use a single arrowuse a single arrow

Strength of conjugate acid – base Strength of conjugate acid – base pairspairs

The stronger the acid the weaker its The stronger the acid the weaker its conjugate base.conjugate base.The stronger the base the weaker its The stronger the base the weaker its conjugate acid.conjugate acid.

The acid dissociation constant KThe acid dissociation constant Kaa

Weak acid HAWeak acid HAHA + HHA + H22O <--> HO <--> H33OO++ + A + A--

KKeqeq = = For a 1 M solution of a typical weak acid may be For a 1 M solution of a typical weak acid may be only .007% of the water molecules react. Move the only .007% of the water molecules react. Move the water to the left side of the equationwater to the left side of the equation

The higher the KThe higher the Kaa the more the reaction goes to the the more the reaction goes to the right . The greater the Kright . The greater the Kaa the stronger the acid the stronger the acidWeak acids have a KWeak acids have a Kaa less than 1 less than 1

Diprotic acidsDiprotic acids

2 step dissociation2 step dissociation

Base dissociation constant KBase dissociation constant Kbb

The base dissociation constant is a The base dissociation constant is a measure of the strength of a basemeasure of the strength of a baseDo calculations of dissociation constantsDo calculations of dissociation constants

ObjectivesObjectives

Explain what most acidic hydrogen atoms Explain what most acidic hydrogen atoms have in commonhave in commonExplain what most bases have in commonExplain what most bases have in commonDescribe how acids are namedDescribe how acids are named

Naming and identifying acids and Naming and identifying acids and basesbases

11stst all H’s are not acidic CH all H’s are not acidic CH44

As a rule an acidic hydrogen already has a As a rule an acidic hydrogen already has a slight positive charge while is it part of a slight positive charge while is it part of a molecule. (It is in the positive side of a molecule. (It is in the positive side of a polar covalent bond)polar covalent bond)Usually bonded with O, N, or a halogen Usually bonded with O, N, or a halogen

3 types of acids3 types of acids

Binary acidsBinary acids - H and 1 other element usually - H and 1 other element usually 6A or 7A6A or 7AStrong HCl, HBr, and HIStrong HCl, HBr, and HIWeak HF, HWeak HF, H22S and HS and H22SeSe

Oxy acids contain H, O and 1 other elementOxy acids contain H, O and 1 other elementHH22SOSO44, HNO, HNO33 and H and H33POPO44

Carboxylic Acid – organic acids COOH groupCarboxylic Acid – organic acids COOH groupAcetic acid HCAcetic acid HC22HH33OO22 vinegar vinegar

BasesBases

A Bronsted-Lowry base always contains an A Bronsted-Lowry base always contains an unshared pair of electrons NHunshared pair of electrons NH33 attracts H attracts H++

Anions: remember conjugate bases HCl ClAnions: remember conjugate bases HCl Cl--

Weak ClWeak Cl-- Br Br-- I I-- NO NO33-- HSO HSO44

-- CIO CIO44--

Strong OStrong O-2-2 OH OH-- PO PO44-3 -3 and CO and CO33

-2-2

Amines N has an unshared pr. Of electronsAmines N has an unshared pr. Of electrons

Naming Acids and BasesNaming Acids and Bases

If the name of an anion ends in ide the If the name of an anion ends in ide the name of the acid that produces it includes name of the acid that produces it includes the name of the anion, a hydo prefixthe name of the anion, a hydo prefixHydrochloric acid – all binary acidsHydrochloric acid – all binary acidsIf the name of an anion ends in ate use If the name of an anion ends in ate use and ic ending Nitric acid, carboxylic acidand ic ending Nitric acid, carboxylic acidAnion ends in ite SOAnion ends in ite SO33

-2-2 sulfite ion H sulfite ion H22SOSO33 sulfurous acid sulfurous acid