Acid –Base Acid –Base Theories 19.1Theories 19.1A. AcidsA. Acids

Describing an AcidDescribing an Acid

Tastes “sour”Tastes “sour” Common compound in fruits and Common compound in fruits and

vegetablesvegetables corrosive corrosive Forms electrolytes when in aqueous Forms electrolytes when in aqueous

solution (ions!)solution (ions!) Is a molecular compoundIs a molecular compound

Explaining Acid BehaviorExplaining Acid Behavior

Acids are Acids are hydrogen containing hydrogen containing substancessubstances, HCl, H, HCl, H22SOSO44

But not all hydrogen containing But not all hydrogen containing compounds are acids!!! CHcompounds are acids!!! CH44, C, C66HH1212OO66

Dissociate (ionize) by releasing H+ ions Dissociate (ionize) by releasing H+ ions (hydrogen ion or proton) into solution.(hydrogen ion or proton) into solution.

written as a dissociation Rxwritten as a dissociation Rx HCl HCl →H→H++ + OH + OH--

Acid Formulas Acid Formulas

Acids are ionic compounds where the Acids are ionic compounds where the cationcation is is H+ (not a metal)H+ (not a metal)

Anion:Anion: Periodic table (how many +/-) and Periodic table (how many +/-) and Memory (polyatomic ions: nitrate, Memory (polyatomic ions: nitrate, hydroxide, carbonate, chlorate, sulfate, hydroxide, carbonate, chlorate, sulfate, phosphatephosphate

Undissociated it is a neutral compoundUndissociated it is a neutral compound

Acid FormulasAcid Formulas

Example: phosphoric acidExample: phosphoric acid Made of phosphate and enough H+ to Made of phosphate and enough H+ to

neutralize itneutralize it Formula of phosphate:Formula of phosphate: POPO44

3-3-

Plus 3 H+Plus 3 H+ HH33POPO44

Types of AcidsTypes of Acids

Contains/releases Contains/releases one ionizable H+one ionizable H+ , , monoprotic acidmonoprotic acid

HCl HCl → H+ + Cl-→ H+ + Cl-Contains/releases Contains/releases two ionizable H+two ionizable H+ , ,

diprotic aciddiprotic acid HH22SOSO44 → 2H+ + SO→ 2H+ + SO44

2-2-

Contains/releases Contains/releases three ionizable H+three ionizable H+ , , triprotic acidtriprotic acid

HH33POPO44 → 3H+ + PO→ 3H+ + PO443-3-

Review ElectronegativityReview Electronegativity

Increases in this directionIncreases in this direction

Why do acids release H+?Why do acids release H+? H involved in H involved in very polar covalent bondsvery polar covalent bonds

–attached to a very electronegative –attached to a very electronegative element are released as H+ ionselement are released as H+ ions

Example HCl: Cl is very electronegativeExample HCl: Cl is very electronegative

H-Cl ---H-Cl --- H H++ + Cl + Cl--

δδ+ + δδ-- On the other hand: CH4 weakly polar On the other hand: CH4 weakly polar

molecule: C is not very electronegative, molecule: C is not very electronegative, does not release an H+!!!does not release an H+!!!

What does the H+ do?What does the H+ do?

Reacts with HReacts with H22O to form an O to form an hydronium hydronium

ionion H H33O+O+

a. H+ + Ha. H+ + H22O O → → HH33OO+ +

Hydrochloric acid Hydrochloric acid (hydrogen chloride)(hydrogen chloride)

HClHCl MonoMonoprotic acidprotic acid

H - Cl H - Cl

HCl HCl → H→ H++ + Cl + Cl--

Nitric AcidNitric Acid

HNOHNO33

Monoprotic acidMonoprotic acid HNOHNO3 3 →→H+ + NOH+ + NO33

--

Carbonic AcidCarbonic Acid

HH22COCO33

Diprotic acidDiprotic acid HH22COCO3 3 →2→2H+ + COH+ + CO33

2-2-

Phosphoric AcidPhosphoric Acid

HH33POPO44

Triprotic acidTriprotic acid HH33POPO44 →3 →3 H+ + POH+ + PO44

3-3-

Sulfuric AcidSulfuric Acid

HH22SOSO44

Diprotic acidDiprotic acid HH22SOSO44→ 2H+ + → 2H+ + SOSO44

2-2-

Formulas of Organic Acids-Formulas of Organic Acids-Acids of HydrocarbonsAcids of Hydrocarbons

Example: CHExample: CH33COOHCOOH

Not all hydrogens are released!Not all hydrogens are released! Which bonds are high/low polarWhich bonds are high/low polar

very polarvery polar

Weak polarWeak polar Monoprotic Monoprotic

Organic Acids have Organic Acids have Carboxyl GroupsCarboxyl Groups

COOH group is called a COOH group is called a carboxyl groupcarboxyl group

Makes a molecule acidicMakes a molecule acidic Dissociation: Dissociation:

CHCH33COOHCOOH→→CH3COOCH3COO-- + H + H++

Ethanoic Acid (acetic or Ethanoic Acid (acetic or vinegar acid)vinegar acid)

CHCH33COOHCOOH monoprotic acidmonoprotic acid

CHCH33COOHCOOH→H+ +→H+ +CHCH33COOCOO--

B. Describing a BaseB. Describing a Base Adjective: Adjective: basicbasic or or alkalinealkaline rare in nature/foodsrare in nature/foods taste bittertaste bitter are part of soaps –make surfaces are part of soaps –make surfaces

slipperyslippery Corrosive, often more dangerous than Corrosive, often more dangerous than

acidsacids Are part of cleaners, drain openersAre part of cleaners, drain openers Act as electrolyte if aqueousAct as electrolyte if aqueous

Base FormulasBase Formulas

Normal ionic neutral compound: metal Normal ionic neutral compound: metal cation and hydroxide anion (OH-) cation and hydroxide anion (OH-)

Formula ends with OHFormula ends with OH Name ends with ‘hydroxide’Name ends with ‘hydroxide’ NaOH –sodium hydroxideNaOH –sodium hydroxide Give the formula of Calcium HydroxideGive the formula of Calcium Hydroxide Ca(OH)Ca(OH)22

Base BehaviorBase Behavior

Dissociation into metal cation and Dissociation into metal cation and hydroxide ionhydroxide ion, OH- , OH-

A base is a hydroxide donorA base is a hydroxide donor NaOH NaOH → Na+ + OH-→ Na+ + OH-

Sodium Hydroxide NaOHSodium Hydroxide NaOH

Ionic compound Ionic compound Releases OH-Releases OH- NaOH NaOH → Na+ + OH-→ Na+ + OH- Other similar base: KOH (potassium Other similar base: KOH (potassium

hydroxide), CsOH, RbOHhydroxide), CsOH, RbOH

Magnesium hydroxideMagnesium hydroxide

Mg(OH)Mg(OH)22

Mg(OH)Mg(OH)2 2 →→MgMg2+2+ + 2(OH) + 2(OH)--

Similar are Calcium- or BariumhydroxideSimilar are Calcium- or Bariumhydroxide

Ammonia NH3Ammonia NH3

Exceptional base:Exceptional base: Does not directly release OH-Does not directly release OH- Instead breaks water apartInstead breaks water apart NH3 + H2O NH3 + H2O → NH4+ + OH-→ NH4+ + OH-

Testing for Acids and Testing for Acids and BasesBases indicator substances that change colorindicator substances that change color Litmus paperLitmus paper Commercially available test stripsCommercially available test strips

Acids and Bases togetherAcids and Bases together

React with each otherReact with each other neutralizeneutralize form a salt of the base cation and the form a salt of the base cation and the

acid anion and wateracid anion and water

HCl + NaOHHCl + NaOH→ NaCl + H2O→ NaCl + H2O

Practice: Carbonic acid reacts with Calcium Practice: Carbonic acid reacts with Calcium hydroxidehydroxide