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

Definition of Acid and Bases

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

Arrhenius acid Arrhenius base H+ OH-

2

1

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 pair forming dative/coordinate bond with Lewis acid

3

HCI + H2O → CI- + H3O+

H2O donate e- HCI accept e-

Lewis acid Lewis base

Physical properties of Acids

• Substance dissolves in water produce

hydrogen/H+ or hydronuim /H3O+ • HCI → H+ + CI- • Conduct electricity – free moving ions • Sour, pH < 7 • Turns blue litmus red • Turns phenolphthalein colourless • Turns methyl orange to red

Properties of Acids and Bases

Acid + Metal (above H) → Salt + H2 gas 2HCI + Mg → MgCI2 + H2

Acid + Base → Salt + Water + product. Bases are - Metal Hydroxide, Metal Oxide, Metal Carbonates Acid + Metal Hydroxide → Salt + Water Acid + Metal Oxide → Salt + Water Acid + Metal Carbonate → Salt + Water + Carbon Dioxide

Acid + Ammoniaaq and Amines → Salt + water HCI + NH4OH → NH4CI + H2O

HCI + CH3NH2 → CH3NH3 + CI-

Chemical properties of Acids / Bases

Physical properties of Acids

Physical properties of Bases • Substance dissolves in water produce hydroxide/OH- ion • NaOH → Na+ + OH- • Conduct electricity – free moving ions • Bitter, pH > 7 • Turns red litmus blue

• Turns phenolphthalein pink

• Turns methyl orange to yellow

Physical properties of Bases

Physical Properties Chemical Properties Physical Property

Chemical Property

Physical properties of Acids

• Electrolytes, produces H3O+, hydronium ion

• Conduct electricity • Sour, pH < 7 • Turns litmus red, • Turns phenolphthalein colourless • Turns methyl orange to red

Physical properties of Bases

• Bitter, pH > 7

• Turns litmus blue • Turns phenolphthalein pink • Turns methyl orange to yellow

Physical/Chemical Properties of Acids and Bases

Acid with Metal → Salt + H2 gas 2HCI + Mg → MgCI2 + H2

Acid with Base (Neutralization) → Salt + Water Bases are - Metal Hydroxide, Metal Oxide, Metal Carbonates Acid + Metal Hydroxide Acid + Metal Oxide Acid + Metal Carbonate

Acid with Ammonia(aq) and Amines → Salt + water HCI + NH4OH → NH4CI + H2O

HCI + CH3NH2 → CH3NH3 + CI-

Chemical properties of Acids / Bases Physical properties of Acids/Bases

Bases

Acid + Metal Hydroxide (Alkali) → Salt + Water LiOH + HCI → LiCI + H2O

NaOH + HNO3 → NaNO3 + H2O

KOH + H2SO4 → K2SO4 + H2O

Acid + Metal Hydroxide (Insoluble) → Salt + Water Ca(OH)2 + 2HCI → CaCI2 + 2H2O

Fe(OH)2 + 2HNO3 → Fe(NO3)2 + 2H2O

Mg(OH)2 + H2SO4 → MgSO4 + 2H2O

Acid + Metal Oxide → Salt + Water CaO + 2HCI → CaCI2 + H2O

CuO + 2HCI → CuCI2 + H2O

Acid + Alkali

Acids + Metal Oxide

Acid + Metal Hydroxide

Acid + Metal Carbonate

Acid +Metal Carbonate → Salt, Water + CO2

CaCO3 + 2HCI → CaCI2 + H2O + CO2

CuCO3 + 2HCI → CuCI2 + H2O + CO2

CH3COOH ↔ H+ + CH3COO-

(1 mole) (0.01 mole)

Strong Acid / Base Weak Acid / Base

Strong acid – ionise/dissociate completely producing H+ ion Strong base – ionise/dissociate completely producing OH- ion All are in ions state, NO molecule left Strong electrolyte with high conductivity ↑

Weak acid – ionise/dissociate partially producing H+ ion Weak base – ionise/dissociate partially producing OH- ion Most in undissociated molecule form Poor electrolyte with low conductivity ↓

HCI → H+ + CI- HBr → H+ + Br−

Monoprotic acid - 1 mole H+ ions

Diprotic acid - 2 mole H+ ions

H2SO4 → 2H+ + SO42-

(1 mole) (2 mole)

Strong Acid - HI, HBr, HCI, HNO3, H2SO4, HCIO3, HCIO4

Strong Base - LiOH, KOH, NaOH, CsOH, Ca(OH)2, Ba(OH)2 Weak Acid - CH3COOH, HF, HCN, H2CO3, H3BO3, HNO2, H3PO4

Weak Base - NH3, C2H5NH2 , CH3NH2, (CH3)2NH, C3H5O2NH2

Weak acid dissociate partially produce few H+ ion

NH3 + H2O ↔ NH4+ + OH-

C2H5NH2 + H2O ↔ C2H5NH3+ + OH-

CO32- + H2O ↔ HCO3

- + OH-

Weak base dissociate partially produce few OH- ion

Vs

Example of Strong Acid/Base Example of Weak Acid/Base

Ba(OH)2 → Ba2+ + 2OH−

(1 mole) (2 mole)

(1 mole) (1 mole) Dissociate completely No molecules left All ions form Few ions

form Dissociate partially Molecules left

Monoprotic base - Accept 1 mole H+ ions by 1 mole OH-

Na(OH) → Na+ + OH−

(1 mole) (1 mole)

All ions form

Dissociate completely No molecules left

Few ions form

Dissociate partially Molecules left

H3PO4 ↔ H+ + H2PO4

-

H2PO4- ↔ H+ + HPO4

2-

HPO42- ↔ H+ + PO4

3- H3PO4

↔ 3H+ + PO43-

Diprotic base - Accept 2 mole H+ ions by 2 mole OH-

Weak triprotic acid dissociate partially produce few H+ ion

CH3COOH ↔ H+ + CH3COO-

(1 mole) (0.01 mole)

Strong Acid / Base Weak Acid / Base

Strong acid – ionise/dissociate completely producing H+ ion Strong base – ionise/dissociate completely producing OH- ion All are in ionic ions state Strong electrolyte with high conductivity ↑

Weak acid – ionise/dissociate partially producing H+ ion Weak base – ionise/dissociate partially producing OH- ion Most in undissociated molecule form Poor electrolyte with low conductivity ↓

HCI → H+ + CI- HBr → H+ + Br−

Monoprotic acid - produce 1 mole H+ ions

Diprotic acid - 2 mole of H+

H2SO4 → 2H+ + SO42-

Strong acid - HI, HBr, HCI, HNO3, H2SO4, HCIO3, HCIO4

Strong base - LiOH, KOH, NaOH, CsOH, Ca(OH)2, Ba(OH)2

(1 mole) (2 mole)

Weak Acid - CH3COOH, HF, HCN, H2CO3, H3BO3, HNO2, H3PO4

Weak Base - NH3, C2H5NH2 , CH3NH2, (CH3)2NH, C3H5O2NH2

Weak acid dissociate partially produce few H+ ion

NH3 + H2O ↔ NH4+ + OH-

C2H5NH2 + H2O ↔ C2H5NH3+ + OH-

CO32- + H2O ↔ HCO3

- + OH-

Weak bases dissociate partially produce few OH- ion

Vs

Example Strong Acid/Base Example Weak Acid/Base

Concentrated Acid / Base Diluted Acid / Base

Concentrated Acid – High number of moles/amt of solutes per dm3

1 M HCI – 1 mole of HCI molecules in 1 dm3

10 M HCI – 10 moles of HCI molecules in 1 dm3

Diluted Acid – Low number of moles/amt of solutes per dm3

0.1M HCI – 0.1 mole of HCI molecules in 1 dm3

0.01M HCI – 0.01 moles of HCI molecules in 1 dm3

Concentrated Acid may not be a Strong Acid 10M CH3COOH – Concentrated Acid ↑ but Weak Acid ↓

Diluted Acid may be a Strong Acid 0.01M HCI – Diluted Acid ↓ but Strong Acid ↑

10M CH3COOH - CONCENTRATED WEAK acid because 10M acid molecule will dissociate partially forming few H+ ions

0.01M HCI - DILUTED STRONG acid because all 0.01M acid molecule dissociate fully forming H+ ions

Vs

Diprotic base - 2 mole of OH-

Ba(OH)2 → Ba2+ + 2OH−

(1 mole) (2 mole)

(1 mole) (1 mole)

Easier using pH scale than Conc [H+] • Conc H+ increase 10x from 0.0001(10-4) to 0.001(10-3) - pH change by 1 unit from pH 4 to 3 • pH 3 is (10x) more acidic than pH 4 • 1 unit change in pH is 10 fold change in Conc [H+]

Conc OH- increase ↑ by 10x – pH increase ↑ by 1 unit

pOH with Conc OH-

pOH = -log [OH-] [OH-] = 0.0000001M pOH = -log [0.0000001] pOH = -log1010-7 pOH = 7 pH + pOH = 14 pH + 7 = 14 pH = 7 (Neutral)

pH with Conc H+

pH = -log [H+] [H+] = 0.0000001M pH = -log [0.0000001] pH = -log1010-7

pH = 7 (Neutral)

Conc H+ increase ↑ by 10x – pH decrease ↓ by 1 unit

pH measurement of Acidity of solution

• pH is the measure of acidity of a solution in logarithmic scale •pH = power of hydrogen or minus logarithm to base ten of hydrogen ion concentration

← Acidic – pH < 7 Alkaline – pH > 7 →

pOH with Conc OH-

pOH = -log [OH-] [OH-] = 0.1M pOH = -log[0.1] pOH = 1 pH + pOH = 14 pH + 1 = 14

pH = 13 (Alkaline)

pH with Conc H+

pH = -log [H+] [H+] = 0.01M pH = -log [0.01] pH = -log1010-2

pH = 2 (Acidic)

Easier scale

pH measurement of Acidity of solution

H2O dissociate forming H3O+ and OH- (equilibrium exist)

• H2O + H2O ↔ H3O+ + OH− • Kc = [H3O+][OH−]/[H2O]2

• Kc [H2O]2 = [H3O+][OH−] Dissociation H2O small, conc [H2O] is constant Kc [H2O]2 is constant called Kw = [H3O+][OH−] Kw = 1.0 x 10-14 mol2 dm-6 - dissociation constant water at -25C Kw = [H3O+][OH−] 1.0 x 10-14 = [H3O+][OH−] 1.0 x 10-14 = [1.0 x 10-7][1.0 x 10-7] [H3O+]= 1.0 x 10-7, [OH-] = 1.0 x 10-7 Conc [H+] = 1 x 10-12

pH = -lg[H+] pH = -lg [10-12] pH = 12

Conc [OH-] = 1 x 10-2 pOH = -log10[OH-]

= -log1010-2 pOH = 2 pH + pOH = 14 pH + 2 = 14 pH = 12

Conc [H+] = 1 x 10-2 pH = -lg[H+] pH = -lg [10-2] pH = 2

Alkaline Alkaline

Acidic Acidic

Kw - dissociation constant water - ionic product water

Using conc [H+] pH = -log10[H+]

pH = -log10[H+] pOH = -log10[OH-] pH + pOH = 14 Kw = [H+][OH-]

Using conc [OH-] pOH = -log10[OH-]

Conc [OH-] = 1 x 10-12 pOH = -log10[OH-]

= -log1010-12 pOH = 12 pH + pOH = 14 pH + 12 = 14 pH = 2

Formula for acid/base calculation

Dissociation Constant or Ionic Product Constant Water, Kw

Kw - Dissociation water is endothermic and Temp dependent H2O + H2O ↔ H3O+ + OH− ΔH = +57kJ/mol Kw = [H3O+][OH−] Temp increases, equilibrium shift to right (endo), so more ions form, Kw increases ↑

Temp ↑ - shift to right – more H+/OH- – Kw ↑ Relationship – Temp ↑/ Kw ↑/Neutral pH ↓ Temp ↑ - Kw ↑ – H+ ion ↑ - pH ↓

H2O + H2O ↔ H3O+ + OH− ΔH = +57kJ/mol

At 25C, Kw - 1.0 x 10-14

•Kw = [H+][OH−] • 1.0 x 10-14 = [H+][OH−] • [H+][OH−] = [10-7][10-7] • pH = -lg[H+] • pH = -lg [1.0 x 10-7] • Neutral pH = 7

At 50C, Kw - 9.3 x 10-14

•Kw = [H+][OH−] •9.3 x 10-14 = [H+][OH−] •[H+]2 = 9.3 x 10-14 •[H+] = 3.05 x 10-7 • pH = -lg[3.05 x 10-7] • Neutral pH = 6.5

At 50C - pH 6.5 is NEUTRAL • Conc of [H+] and [OH−] the same • [H+] = [OH-] = 3.05 x 10-7

H2O dissociate forming H3O+ and OH- (equilibrium exist)

• H2O + H2O ↔ H3O+ + OH− • Kw = [H3O+][OH−]/[H2O]2 Dissociation H2O is small, conc [H2O] is constant - Kw = [H3O+][OH−] Kw = 1.0 x 10-14 mol2 dm-6 - dissociation constant water at -25C Kw = [H3O+][OH−] 1.0 x 10-14 = [H3O+][OH−] 1.0 x 10-14 = [1.0 x 10-7][1.0 x 10-7] [H3O+]= 1.0 x 10-7, [OH-] = 1.0 x 10-7

At 25C - pH 7 is NEUTRAL • Conc of [H+] and [OH−] the same • [H+] = [OH-] = 1.00 x 10-7

Calculate conc of OH- and pH for 0.001 HCI. HCI → H+ + CI- (100% dissociate) 0.001 0.001 Kw = [H+][OH−] = 10-14 (assume all H+ from HCI and H+ from water is negligible) [0.001][OH-] = 10-14 [OH-] = 10-14/0.001 = 10 -11

pH = -log1o[H]+ =-log10o.oo1

pH = 3

Calculate conc of OH- when 3.o x 10-4 [H+] was added to pure water HCI → H+ + CI- (100% dissociate) 3.o x 10-4 3.o x 10-4 Kw = [H+][OH−] = 10-14 (assume all H+ from HCI and H+ from water is negligible) [OH] = 10-14 = 10 -14 = 3.3 x 10 -11 M

[H+] 3.o x 10-4

What is the pH for [H+] = 10-12 M pH = -lg[H+] pH = -lg [10-12] pH = 12

What is the conc of H+ in solution with pH 3? pH = -lg[H+] 3 = -lg[H+] [H+] = 10 –pH

[H+] = 10 -3

What is the pH for [OH-] = 0.1 M pOH = -lg[OH-] pOH = -lg [0.1] pOH = 1 pH + pOH = 14 pH = 14 – 1 = 13

What is the pH of 1.0M NaOH ? NaOH → Na+ + OH- (100% dissociate) 1M 1M 1M Kw = [H3O+][OH−] = 10-14 (assume all OH- from NaOH and OH- from water is negligible) [H+] = 10-14 = 10 -14 = 1.0 x 10 -14

[OH] 1.0 pH = -log [H+] pH = -log [1.0 x 10 -14] pH = 14

Acid/base Calculation

pH = -log10[H+] pOH = -log10[OH-] pH + pOH = 14 Kw = [H+][OH-]

Formula acid/base calculation

Questions on Acids and Base

Which list contains only strong acids ?

A. CH3COOH, H2CO3, H3PO4

B. HCI, HNO3, H2CO3

C. CH3COOH, HNO3, H2SO4

D. HCI, HNO3, H2SO4

When equal volume of four 1M solutions are arranged in order of increasing pH (lowest pH first), what is the correct order?

A. CH3COOH < HNO3 < CH3CH2NH2 < KOH

B. HNO3 < CH3COOH < CH3CH2NH2 < KOH

C. CH3CH2NH2 < HNO3 < CH3COOH < KOH

D. KOH < CH3CH2NH2 < CH3COOH < HNO3

pH of a solution changes from pH =2 to pH =5. What happens to the concentration of H+ ions during this pH change?

A. Decrease by factor of 1000

B. Increase by factor of 1000

C. Decrease by factor of 100

D. Increase by a factor of 100

Solution of acid A has a pH of 1 and a solution of acid B has a pH of 2. Which statement is correct ?

A. Acid A is stronger than acid B

B. [A] > [B]

C. Concentration of H+ ions in A is higher than B

D. Concentration of H+ ions in B is twice the concentration of H+ in A

100ml of NaOH solution of pH 12 is mixed with 900ml of water. What is the pH of resulting solution?

A. 1

B. 3

C. 11

D. 13

1

2

3

4

5

О

О

О

О

О

List two ways to distinguish between strong and weak acid/base 6

By Conductivity measurement

1M Strong Acid – Ionise completely – More H+ ion – pH lower ↓ 1M Weak Acid – Ionise partially – Less H+ ion – pH higher ↑

1M Strong Acid – Ionise completely – More H+ ion – Conductivity higher ↑ 1M Weak Acid – Ionise partially – Less H+ ion – Conductivity lower ↓

By pH measurement

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

Video on Acid/ Base

Click here on Lewis Acid/Base

Click here on pH varies with temperature Click here on pKa and pKb calculation