Types of Problems

ACIDS, BASES & SALTS

The Arrhenius Theory of Acids and Bases

Arrhenius Theory of Acids and Bases:an acid contains hydrogen and ionizes in solutions to produce H+ ions:

HCl H+(aq) + Cl-(aq)Arrhenius Theory of Acids and Bases:a base contains an OH- group and ionizes in solutions to produce OH- ions:

NaOH Na+(aq) + OH-(aq)NeutralizationNeutralization: the combination of H+ with OH- to form water.

H+(aq) + OH-(aq) H2O (l)

Hydrogen ions (H+) in solution form hydronium ions (H3O+)In RealityH+ + H2O H3O+Hydronium Ion(Can be used interchangeably with H+)Commentary on Arrhenius TheoryOne problem with the Arrhenius theory is that its not comprehensive enough. Some compounds act like acids and bases that dont fit the standard definition.

Bronsted-Lowry Theory of Acids & Bases

Bronsted-Lowry Theory of Acids & Bases:An acid is a proton (H+) donor

A base is a proton (H+) acceptorfor exampleHCl(aq) + H2O(l) H3O+(aq) + Cl-(aq)Proton transferAcidBaseNH3(aq) + H2O(l) NH4+ (aq) + OH- (aq)BASEACIDCONJUGATE ACIDCONJUGATE BASEAmmonia is a proton acceptor, and thus a baseanother exampleWater is a proton donor, and thus an acid.Conjugate acid-base pairsConjugate acid-base pairs differ by one proton (H+)A conjugate acid is the particle formed when a base gains a proton.A conjugate base is the particle that remains when an acid gives off a proton.

Examples: In the following reactions, label the conjugate acid-base pairs:H3PO4 + NO2- HNO2 + H2PO4-

CN- + HCO3- HCN + CO32-

HCN + SO32- HSO3- + CN-

H2O + HF F- + H3O+

acidbasec. acidc. baseacidbasec. acidc. baseacidbasec. acidc. baseacidbasec. acidc. baseAmphoteric SubstancesA substance that can act as both an acid and a base (depending on what it is reacting with) is termed amphoteric.

Water is a prime example.Properties of Acids and BasesACIDSHave a sour tasteChange the color of many indicatorsAre corrosive (react with metals)Neutralize basesConduct an electric currentBASESHave a bitter tasteChange the color of many indicatorsHave a slippery feelingNeutralize acidsConduct an electric currentOther Household Acids and BasesAntacid: a weak base that neutralizes excess stomach acid.

The pH of shampoo is generally kept between 5 and 8.

Lemon juice is an acid that is sometimes used to help keep fruit looking fresh.

What will happen to left apple?

Indicators-Way Cool Cyber-lab:http://www.miamisci.org/ph/phlemon.html

Strength of Acids and BasesA strong acid dissociates completely in soln:HCl H+(aq) + Cl-(aq)A weak acid dissociates only partly in soln:HNO2 H+(aq) + NO2-(aq)A strong base dissociates completely in soln:NaOH Na+(aq) + OH-(aq)A weak base dissociates only partly in soln:NH3(aq) + H2O(l) NH4+(aq) + OH-(aq)

The Lewis Theory of Acids and Bases

The Lewis Theory of Acids & BasesLewis acid: a substance that can accept an electron pair to form a covalent bond (electron pair acceptor).

Lewis base: a substance that can donate an electron pair to form a covalent bond (electron pair donor).

NeutralizationNeutralization: the formation of a coordinate covalent bond in which both electrons originated on the same (donor) atom.Example 1:Ionization of NH3:NH3 + H2O NH4+ + OH-NNHHHOHH+HHHHH+O..........+-acidbaseExample 2:Auto-ionization of water:H2O + H2O H3O+ + OH-OOHHOHH+HHHH+O..........+-acidbase....Example 3:Reaction of NH3 with HBr (a Lewis AND a Bronsted-Lowry acid-base reaction):NH3 + HBr NH4+ + Br-NNHHHBrH+HHHH+Br..........+-acidbaseAcid Base TheoriesLewisBronsted-LowryArrheniusSUMMARY OF ACID-BASE THEORIESTheoryAcid DefinitionBase DefinitionArrhenius TheoryAny substance which releases H+ ions in water solution.Any substance which releases OH- ions in water solutionBrnsted-Lowry TheoryAny substance which donates a proton.Any substance which accepts a proton.Lewis TheoryAny substance which can accept an electron pair.Any substance which can donate an electron pair.Acid-Base ReactionsNeutralization reactions: reactions between acids and metal hydroxide bases which produce a salt and water.

H+ ions and OH- ions combine to form water molecules:

H+(aq) + OH-(aq) H2O(l)Example 1: the reaction of HCl and NaOH (there are 3 ways to write the chemical equation):Balanced formula unit equation:HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq)

Total ionic equation:H+(aq)+Cl-(aq)+Na+(aq)+OH-(aq)H2O(l)+Na+(aq)+Cl-(aq)

Net ionic equation:H+(aq) + OH-(aq) H2O(l)Example 2: Write the 3 types of equations for the reaction of hydrobromic acid, HBr, with potassium hydroxide, KOH.Balanced formula unit equation:HBr(aq) + KOH(aq) H2O(l) + KBr(aq)

Total ionic equation:H+(aq)+Br-(aq)+K+(aq)+OH-(aq) H2O(l)+K+(aq)+Br-(aq)

Net ionic equation:H+(aq) + OH-(aq) H2O(l)Example 3: Write the 3 types of equations for the reaction of nitric acid, HNO3, with calcium hydroxide, Ca(OH)2.Balanced formula unit equation:2HNO3(aq) + Ca(OH)2(aq) 2H2O(l) + Ca(NO3)2(aq)

Total ionic equation:2H+(aq)+2NO3-(aq)+Ca2+(aq)+2OH-(aq)2H2O(l)+Ca2++2NO3-(aq)

Net ionic equation:H+(aq) + OH-(aq) H2O(l)