ACID-BASE THEORIESSection 15 - 2

Objectives1. Define and recognize Bronsted-

Lowry acids and bases.2. Define a Lewis acid and a Lewis

base.3. Name compounds that are acids

under the Lewis definition but are not acids under the Bronsted-Lowry definitions

Bronsted-Lowry Acids and Bases Expansion of Arrhenius acid definition Bronsted-Lowry Acid

Molecule or ion that is a proton donor HCl + NH3 NH4

+ + Cl-

H+ is a proton HCl donates H+ (proton) to NH3

H Cl + H N H H N H + Cl

H H

Bronsted-Lowry Base Molecule or ion that is a proton acceptor

NH3 accepts H+ (proton) from HCl

Bronsted-Lowry acid-base reaction Protons are transferred from one reactant (the

acid) to another (the base)

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+_

H

Monoprotic and Polyprotic Acids

Monoprotic Acid that only donates one proton HCl + H2O H3O+ + Cl-

Polyprotic Acid that can donate more than one

proton per molecule. H2SO4 + H2O H3O+ + HSO4

-

HSO4- + H2O H3O+ + SO4

2-

Diprotic and triproticObvious!

Lewis Acids and Bases Lewis Acid

Atom, ion, or molecule that accepts an electron pair to form a covalent bond. Broadest of 3 definitions

Lewis Base An atom , ion, or molecule that donates an

electron pair to form a covalent bond. Lewis acid-base reaction

Formation of one or more covalent bonds between an electron-pair donor and an electron-pair acceptor

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::F B + N H F B N H F H F H

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::H H

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F F

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