IB Chemistry on Arrhenius, Bronsted Lowry Conjugate Acid Base Pair and Lewis Acid.

Brønsted-Lowry Acid - substance that donates proton/proton donor Bronsted-Lowry Base – substance that accepts proton/proton acceptor One species donate proton – one species accept proton

Arrhenius acid - substance dissociates in water to produce H+ ions. Arrhenius base – substance dissociates in water to produce OH- ions. All Arrhenius acid are Bronsted Lowry acid and water must be present

HCI ↔ H+ + CI-

HCI + H2O ↔ H3O+ + CI-

NaOH → Na+ + OH-

NH3 + H2O ↔ NH4+ + OH-

CO32- + H2O ↔ HCO3

- + OH-

Water/aqueous medium

Water/aqueous medium Other solvent medium possible Involve H atoms

Definition of Acid and Bases

http://4photos.net/en/image:44-225901-Water_droplets_on_blue_backdrop__images

Arrhenius acid Arrhenius base H+ OH-

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gain H

Acid + Base ↔ Conjugate Base + Conjugate Acid

lose H

HCI (acid) - CI- (conjugate base)

lose H

H2O (base) - H3O+ (conjugate acid)

HCI + H2O ↔ CI- + H3O+

gain H

Lewis Acid - substance that accepts electron/electron acceptor, empty orbital/electron deficient Lewis Base – substance that donates electron/electron donor, lone pair electron Lewis Base - donate electron forming dative/coordinate bond with Lewis acid

3

HCI + H2O → CI- + H3O+

H2O donate e- HCI accept e-

Lewis acid Lewis base

Bronsted Base Bronsted Base

Bronsted Base Bronsted Base



HCI ↔ H+ + CI-


NaOH → Na+ + OH-

NH3 + H2O ↔ NH4+ + OH-

CO32- + H2O ↔ HCO3

- + OH-


Water/aqueous medium Other solvent medium possible

Acid and Bases



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Bronsted Base

HPO42- + SO3

2-↔ PO43- + HSO3

- HCOOH + CN- ↔ HCOO- + HCN


NH4+ + CO2

2- ↔ NH3 + HCO3- CH3COOH + H2O ↔ H3O+ + CH3COO-

Brønsted Acid Brønsted Acid



Brønsted Acid

Brønsted Acid

Bronsted Base

HF + H2O ↔ F- + H3O+

Bronsted Base

H2PO4 - + OH- ↔ HPO42- + H2O

Bronsted Base

H2SO4 + N2H5+ ↔ HSO4

- + N2H62+

Brønsted-Lowry Acid - proton donor - Bronsted-Lowry Base – proton acceptor Every acid has a conjugate base - Every base has a conjugate acid Acid donate proton – Base accept proton Conjugate acid has one more H than base - Conjugate base has one fewer H than acid.

Bronsted Lowry Conjugate acid base pair





CH3COOH + H2O ↔ CH3COO- + H3O+


CH3COOH (acid) - CH3COO- (conjugate base)

HF + H2O ↔ F- + H3O+


HF (acid) - F- (conjugate base)

H2SO4 + N2H5+ ↔ HSO4

- +N2H62+

H2SO4 (acid) - HSO4- (conjugate base)

N2H5+ (base) - N2H6

2+(conjugate acid)

HCOOH (acid) - HCOO- (conjugate base)

HCOOH + CN- ↔ HCOO- + HCN

CN- (base) - HCN(conjugate acid)

HPO42- + SO3

2- ↔ PO43- + HSO3

-

HPO42- (acid) - PO4

3- (conjugate base)

SO32- (base) - HSO3

- (conjugate acid)

C O N J U G A T E A C I D B A S E

lose H

lose H

lose H

lose H

lose H

lose H

gain H gain H

gain H gain H

gain H gain H

gain H

lose H

2



HCOOH (acid) - HCOO- (conjugate base)

HCOOH + CN- ↔ HCOO- + HCN

CN- (base) - HCN(conjugate acid)

HPO42- + SO3

2- ↔ PO43- + HSO3

-

HPO42- (acid) - PO4

3- (conjugate base)

SO32- (base) - HSO3

- (conjugate acid)

NH3 + H2O ↔ NH4+ + OH-

H2O (acid) - OH-(conjugate base)

NH3 (base) - NH4+ (conjugate acid)

NH4+ + CO2

2-↔ NH3 + HCO3-

NH4+ (acid) - NH3 (conjugate base)

CO22- (base) - HCO3

- (conjugate acid)

NH3 + H2S ↔ NH4+ + HS- H2PO4

- + OH- ↔ HPO42- + H2O

H2PO4- (acid) - HPO4

2-(conjugate base)

OH- (base) - H2O (conjugate acid)

NH3 (base) - NH4+ (conjugate acid)

H2S (acid) - HS-(conjugate base)

C O N J U G A T E A C I D B A S E

lose H

lose H

lose H

lose H

lose H

lose H

lose H

gain H

gain H

gain H

gain H

gain H

gain H gain H


2

Strong Acid form → Weak Conjugate Base • Strong acid HCI dissociate completely to form Cl− (weak conjugate base) • Cl− weak conjugate base won't accept H+ to form back HCI • HCI + H2O → Cl− + H3O+ (one way )


lose H

gain H


Strong acid (HCI) form

weak conjugate base (CI-)

Weak conjugate base (CI-) will not accept H+ to form back HCI

Weak Acid form → Strong Conjugate Base • CH3COOH weak acid dissociate partially to form CH3COO- (strong conjugate base) • CH3COO- (strong conjugate base) will accept H+ to form back CH3COOH molecule. • CH3COOH + H2O ↔ CH3COO- + H3O+ (reversible)

Weak acid (CH3COOH) form

strong conjugate base (CH3COO-)

Strong conjugate base (CH3COO-) accept H+ to form back CH3COOH


2


lose H

gain H


Strong base (NaOH) form

weak conjugate acid (H2O)

Weak conjugate acid (H2O) will not lose H+ to form back OH-

Weak base (NH3) form

strong conjugate acid (NH4+)

Strong conjugate acid (NH4) lose H+ to form back NH3

Strong Base form Weak Conjugate acid • Strong base NaOH dissociate completely to form OH- • OH- strong base dissolve in water to form H2O (weak conjugate acid) • OH- + H2O → H2O + OH- ( one way) • H2O (weak conjugate acid ) will not lose H+ to form back OH-

Weak Base form Strong Conjugate Acid NH3 weak base dissociate partially to form NH4

+ (strong conjugate acid) NH3 + H2O ↔ NH4

+ + OH-

NH4+ (strong conjugate acid) lose H+ to form back NH3

NH3 + H2O ↔ NH4+ + OH- (reversible)


2

Conjugate Acid

Conjugate Base

H2SO4 HSO4

HCI CI-

H2SO3 HSO3-

HF F-

HNO2 NO2-

CH3COOH CH3COO-

Conjugate Base

Conjugate Acid

OH- H2O

PO43- HPO4

2-

CO32- HCO3

-

NH3 NH4+


Strong Base + Acid → Weak Conjugate Acid + Conjugate Base

Strong acid

Weak acid

Weak conjugate base

Strong conjugate base

Strong base

Weak base Strong conjugate acid

Weak conjugate acid

Strong Acid + Base → Weak Conjugate Base + Conjugate Acid

Weak Acid + Base ↔ Strong Conjugate Base + Conjugate Acid

Weak Base + Acid ↔ Strong Conjugate Acid + Conjugate Base

reversible

reversible

one way

one way

reversible

reversible

reversible

H2O (amphiprotic) - act as acid or base

H2O + HCI ↔ H3O+ + CI-

HCO3- – Base, proton acceptor

HSO4- – Base, proton acceptor


gain H lose H

H2O – Acid, proton donor H2O – Base, proton acceptor

HCO3- (amphiprotic) - act as acid or base

HCO3- – Acid, proton donor

H2O + NH3 ↔ NH4+ + OH-

HCO3- + OH- ↔ CO3

2- + H2O

lose H

HCO3- + H3O+ ↔ H2CO3 + H2O

gain H

HSO4- (amphiprotic) - act as acid or base

HSO4- – Acid, proton donor

HSO4- + H2O ↔ H3O+ + SO4

2-

lose H

HSO4- + HCI ↔ H2SO4 + CI-

gain H

Amphiprotic substance : • Involve only H+

• Able to donate H+ or gain H+ ions

• Act as acid or base • All amphiprotic are amphoteric

Amphoteric substance: • Act as acid or base • Does not involve only H+ ions • Al2O3 is amphoteric – have no H+ ions • Al2O3(base) + 6HCI → 2AICI3 + 3H2O • AI2O3(acid) + 2NaOH + 3H2O → 2NaAl(OH)4

amphiprotic

amphoteric

Lewis Acid/Base


HCI accept e-


BF3 + NH3 → BF3 – NH3

BF3 accept e-

NH3 donate e-

Molecule acting as Lewis Acid/Base


HF accept e-

CN- donate e-


HCOOH accept e-

HF + H2O ↔ F- + H3O+

H2O donate e-

F

Lewis base Lewis acid

F

HCOOH + :CN- ↔ HCOO- + HCN

Lewis Acid - substance that accepts electron/electron acceptor, empty orbital/electron deficient Lewis Base – substance that donates electron/electron donor, lone pair electron Lewis Base - donate electron pair forming dative/coordinate bond with Lewis acid

H2O donate e-

3

SO2 + H2O → H2SO3

SO2 accept e- CO2 accept e-

Molecule acting as Lewis Acid/Base



H2O + :O2- → 2OH-

O2- donate e-

H2O accept e-


CH3COOH accept e-

CO2 + H2O → H2CO3

H2O donate e-


H2O donate e-

CH3COOH + H2O ↔ CH3COO- + H3O+

H2O donate e-

Lewis Acid/Base


3

Metal Ion as Lewis Acid Ligand as Lewis Base


Fe3+ + :SCN- → [FeSCN]2+

SCN- donate e-

Fe3+ accept e-

H2O donate e-

Fe3+ + 6H2O → [Fe(H2O)]3+


Fe3+ accept e-

AI(OH)3 + OH- → AI(OH)4

-

OH- donate e-

AI3+ accept e-


Ni2+ + :6NH3 → [Ni(NH3)6]2+

NH3 donate e-

Ni2+ accept e-


Lewis Acid/Base


3

Metal Ion as Lewis Acid Ligand as Lewis Base


Fe3+ + :SCN- → [FeSCN]2+

SCN donate e-

Fe3+ accept e-

H2O donate e-

Fe3+ + 6H2O → [Fe(H2O)]3+


Fe3+ accept e-

Metal Ion as Lewis Acid • electron acceptor • high charge density • empty 3d orbitals • attract ligands

Ligand as Lewis Base • electron donor • lone electron pair • dative bond with metal

For following species, state whether it behave as Lewis acid or Lewis base

a) PH3

b) BCI3

c) H2S d) SF4

e) Cu2+

a) PH3 – P (gp 5) - 1 lone pair electron – electron donor – Lewis base b) BCI3 – B (gp 3) - electron deficient/incomplete valence shell – electron acceptor – Lewis acid c) H2S – S (gp 6) - 2 lone pair electron – electron donor – Lewis base d) SF4 – S (gp 6) - 1 lone pair electron – electron donor – Lewis base e) Cu2+ - (transition metal) – high charge density/incomplete 3d orbital – electron acceptor – Lewis acid

Lewis Acid/Base


Question Answer

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HCI ↔ H+ + CI-


NaOH → Na+ + OH-

NH3 + H2O ↔ NH4+ + OH-

CO32- + H2O ↔ HCO3

- + OH-


Water/aqueous medium Other solvent medium possible Involve H atoms




2

1

gain H


lose H


lose H



gain H

Lewis Acid - substance that accepts electron/electron acceptor, empty orbital/electron deficient Lewis Base – substance that donates electron/electron donor, lone pair electron Lewis Base - donate electron forming dative/coordinate bond with Lewis acid

3


H2O donate e- HCI accept e-


Lewis Acid/Base


Bronsted – Lowry

Acid/Base

Arrhenius Acid/Base

Arrhenius acid/base • too limit/narrow definition • only water medium • substance must have H atoms

Bronsted Lowry acid/base • broader definition • proton donor/acceptor • other solvent medium • substance must have H atoms

Lewis acid/base • broader definition • electron acceptor/donor • doesn’t need to have H atoms

All Arrhenius acid are Bronsted Lowry acid and all Bronsted Lowry acid are Lewis acid

Click here on pH calculation Click here on Bronsted Lowry and Lewis Acid/Base

Video on Acid/ Base

Click here on Lewis Acid/Base

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IB Chemistry on Arrhenius, Bronsted Lowry Conjugate Acid Base Pair and Lewis Acid.

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Transcript of IB Chemistry on Arrhenius, Bronsted Lowry Conjugate Acid Base Pair and Lewis Acid.