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Asam dan Basa Bronsted Pasangan asam-basa konjugat : suatu asam dan basa konjugatnya atau suatu basa dan asam konjugatnya Basa konjugat : suatu asam Bronsted ialah spesi yang tersisa ketika satu proton pindah dari asam tersebut. Asam konjugat dihasilkan dari penambahan sebuah proton pada basa bronsted

A __________________ acid is a proton donor A __________________ base is a proton acceptor base acid acid base conjugate acid conjugate base base acid 16.1

Acid-Base Properties of Water H2O (l) H+ (aq) + OH- (aq) Autoionisasi air O H + - [ ] conjugate acid base H2O + H2O H3O+ + OH- conjugate base acid 16.2

Air berfungsi sebagai basa dalam reaksi-reaksi dengan asam HCl Berfungsi sebagai asam dalam NH3

The Ion Product of Water Kc = [H+][OH-] [H2O] H2O (l) H+ (aq) + OH- (aq) [H2O] = constant Kc[H2O] = Kw = [H+][OH-] Konstanta kesetimbangan Kw dinamakan hasil kali antara konsentrasi molar ion H+ dan ion OH- pada suhu tertentu Solution Is [H+] = [OH-] netral At 250C Kw = [H+][OH-] = 1,0 x 10-14 [H+] > [OH-] asam [H+] < [OH-] basa

Kw = [H+][OH-] = _____________ What is the concentration of OH- ions in an HCl solution whose hydrogen ion concentration is 1.3 M? Kw = [H+][OH-] = _____________ [H+] = _____________M [OH-] = Kw [H+] = = _____________ M 16.2

pH – A Measure of Acidity pH = - log [H3O+] atau pH = - log [H+] Solution Is At 250C neutral [H+] = [OH-] [H+] = 1 x 10-7 pH = 7 acidic [H+] > [OH-] [H+] > 1 x 10-7 pH < 7 basic [H+] < [OH-] [H+] < 1 x 10-7 pH > 7 pH [H+] 16.3

-(log [H+] + log [OH-]) =- log (1,0x 10-14) pHs of some common fluids pOH = -log [OH-] [H+][OH-] = Kw = 1,0 x 10-14 -(log [H+] + log [OH-]) =- log (1,0x 10-14) -log [H+] – log [OH-] = 14,00 pH + pOH = 14,00 16.3

-antilog (pH) = -antilog (-log [H+]) The pH of rainwater collected in a certain region of the northeastern United States on a particular day was 4.82. What is the H+ ion concentration of the rainwater? pH = -log [H+] -antilog (pH) = -antilog (-log [H+]) antilog -4.82 = [H+] [H+] = 10-pH = 10-4.82 = _____________ M 16.3

The OH- ion concentration of a blood sample is 2. 5 x 10-7 M The OH- ion concentration of a blood sample is 2.5 x 10-7 M. What is the pH of the blood? pH + pOH = _________ pOH = -log [OH-] = -log (2.5 x 10-7) = _________ pH = 14.00 – pOH = 14.00 – 6.60 = _________ 16.3

Strong Electrolyte = terionisasi sempurna dalam air Kekuatan Asam dan Basa Strong Electrolyte = terionisasi sempurna dalam air NaCl (s) Na+ (aq) + Cl- (aq) H2O Weak Electrolyte = terionisasi hanya sedikit dalam air CH3COOH CH3COO- (aq) + H+ (aq) Strong Acids are strong electrolytes HCl (aq) + H2O (l) H3O+ (aq) + Cl- (aq) HNO3 (aq) + H2O (l) H3O+ (aq) + NO3- (aq) HClO4 (aq) + H2O (l) H3O+ (aq) + ClO4- (aq) H2SO4 (aq) + H2O (l) H3O+ (aq) + HSO4- (aq) 16.4

Weak Acids are weak electrolytes HF (aq) + H2O (l) H3O+ (aq) + F- (aq) HNO2 (aq) + H2O (l) H3O+ (aq) + NO2- (aq) HSO4- (aq) + H2O (l) H3O+ (aq) + SO42- (aq) H2O (l) + H2O (l) H3O+ (aq) + OH- (aq) Strong Bases are strong electrolytes NaOH (s) Na+ (aq) + OH- (aq) H2O KOH (s) K+ (aq) + OH- (aq) H2O Ba(OH)2 (s) Ba2+ (aq) + 2OH- (aq) H2O 16.4

Weak Bases are weak electrolytes F- (aq) + H2O (l) OH- (aq) + HF (aq) NO2- (aq) + H2O (l) OH- (aq) + HNO2 (aq) Conjugate acid-base pairs: Jika asamnya kuat, basa konjugatnya sangat lemah H3O+ is the strongest acid that can exist in aqueous solution. The OH- ion is the strongest base that can exist in aqueous solution. 16.4

Relative Strengths of Conjugate Acid-Base Pairs 16.4

Strong Acid Weak Acid 16.4

What is the pH of a 1.8 x 10-2 M Ba(OH)2 solution? Ba(OH)2 is a strong base – 100% dissociation. Start 0.018 M 0.0 M 0.0 M Ba(OH)2 (s) Ba2+ (aq) + 2OH- (aq) End 0.0 M 0.018 M 0.036 M pH = 14.00 – pOH = 14.00 + log(0.036) = _______ 16.4

Weak Acids (HA) and Acid Ionization Constants HA (aq) + H2O (l) H3O+ (aq) + A- (aq) HA (aq) H+ (aq) + A- (aq) Ka = Ka is the acid ionization constant weak acid strength Ka 16.5

Asam Lemah dan Konstanta Ionisasi Asam HA(aq) + H2O(l)  H3O+(aq) + A-(aq) Konstanta kesetimbangan untuk ionisasi asam dinamakan Konstanta ionisasi asam = Ka Ka = [H3O+] [A-]/[HA] Ka = [H+] [A-]/[HA] Pada suhu tertentu , kekuatan asam HA diukur secara kuantitatif dengan Ka, semakin besar Ka semakin kuat asamnya artinya semakin tinggi konsentrasi ion H+ pada kesetimbangan karena ionisasinya

Ionization Constants of Some Weak Acids and Their Conjugate Bases at 25ºC 16.5

Kita dapat menghitung Ka dari konsentrasi awal asam dan pH larutan, dan kita dapat menggunakan Ka dan konsentrasi awal asam untuk menghitung konsentrasi kesetimbangan semua spesi dan pH larutan Dalam al ini tiga tahap dasarnya adalah : Nyatakan konsentrasi kesetimbangan dari semua spesi dalam konsentrasi-konsentrasi awalnya dan satu bilangan tak diketahui x, yang menyatakan perubahan konsentrasi Tuliskan konstanta ionisasi asam dalam konsentrasi-konsentrasi kesetimbangannya dengan mengetahui nilai Ka kita dapat menentukan x Setelah menentukan x, hitunglah konsentrasi kesetimbangan dari semua spesi dan/atau pH larutan

What is the pH of a 0.5 M HF solution (at 250C)? Ka = [H+][F-] [HF] = 7.1 x 10-4 HF (aq) H+ (aq) + F- (aq) HF (aq) H+ (aq) + F- (aq) Initial (M) 0.50 0.00 0.00 Change (M) -x +x +x Equilibrium (M) Ka = = __________ Ka << 1 0.50 – x  0.50 Ka  = __________ x2 = __________ x = _______M [H+] = [F-] = 0.019 M pH = -log [H+] = _________ [HF] = 0.50 – x = 0.48 M 16.5

When can I use the approximation? Ka << 1 0.50 – x  0.50 When x is less than 5% of the value from which it is subtracted. 0.019 M 0.50 M x 100% = 3.8% Less than 5% Approximation ok. x = 0.019 What is the pH of a 0.05 M HF solution (at 250C)? Ka  x2 0.05 = 7.1 x 10-4 x = 0.006 M 0.006 M 0.05 M x 100% = 12% More than 5% Approximation not ok. Must solve for x exactly using quadratic equation or method of successive approximation. 16.5

What is the pH of a 0.122 M monoprotic acid whose Ka is 5.7 x 10-4? HA (aq) H+ (aq) + A- (aq) Initial (M) 0.122 0.00 0.00 Change (M) -x +x +x Equilibrium (M) Ka = = __________ Ka << 1 0.122 – x  0.122 Ka  = __________ x2 = _________ x = _______ M 0.0083 M 0.122 M x 100% = 6.8% More than 5% Approximation not ok. 16.5

Ka = x2 0.122 - x = 5.7 x 10-4 x2 + 0.00057x – 6.95 x 10-5 = 0 -b ± b2 – 4ac  2a x = ax2 + bx + c =0 x = 0.0081 x = - 0.0081 HA (aq) H+ (aq) + A- (aq) Initial (M) Change (M) Equilibrium (M) 0.122 0.00 -x +x 0.122 - x x [H+] = x = 0.0081 M pH = -log[H+] = 2.09 16.5

pH larutan 0,1 M asam benzoat adalah 2,60. berapa Ka asam itu? pH larutan asam lemah monoprotik 0,060 M ialah 3,44. hitunglah Ka asam ini? Hitunglah pH larutan asam nitrit (HNO2) 0,052 M jika diketahui Ka = 4,5 x 10-4

Weak Bases and Base Ionization Constants NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq) Kb = [NH4+][OH-] [NH3] Kb is the base ionization constant weak base strength Kb Solve weak base problems like weak acids except solve for [OH-] instead of [H+]. 16.6

Ionization Constants of Some Weak Bases and Their Conjugate Bases at 25ºC 16.6

Berapa pH larutan amoniak 0,4 M? (Kb = 1,8 x 10-5) Berapa pH larutan metilamina 0,26 M (Kb = 4,4 x 10-4)

Ionization Constants of Conjugate Acid-Base Pairs HA (aq) H+ (aq) + A- (aq) Ka A- (aq) + H2O (l) OH- (aq) + HA (aq) Kb H2O (l) H+ (aq) + OH- (aq) Kw KaKb = __Kw___ Weak Acid and Its Conjugate Base Ka = Kw Kb Kb = Kw Ka Hubungan antara konstanta-konstanta ionisasi asam-basa konjugat 16.7

Contoh pada asam asetat !!!!

Acid-Base Properties of Salts Neutral Solutions: Salts containing an alkali metal or alkaline earth metal ion (except Be2+) and the conjugate base of a strong acid (e.g. Cl-, Br-, and NO3-). NaCl (s) Na+ (aq) + Cl- (aq) H2O Basic Solutions: Salts derived from a strong base and a weak acid. CH3COONa (s) Na+ (aq) + CH3COO- (aq) H2O CH3COO- (aq) + H2O (l) CH3COOH (aq) + OH- (aq) 16.10

Acid-Base Properties of Salts Acidic Solutions: Salts derived from a strong acid and a weak base. NH4Cl (s) NH4+ (aq) + Cl- (aq) H2O NH4+ (aq) NH3 (aq) + H+ (aq) 16.10

Acid-Base Properties of Salts Solutions in which both the cation and the anion hydrolyze: Kb for the anion > Ka for the cation, solution will be ________ Kb for the anion < Ka for the cation, solution will be ________ Kb for the anion  Ka for the cation, solution will be ________ Acid-Base Properties of Salts 16.10

Hitunglah pH larutan natrium asetat 0,15 M Hitunglah pH larutan natrium asetat 0,15 M. berapakah persen hidrolisisnya?(Kb CH3COO- = 5,6 x 10-10) Hitunglah pH larutan natrium format (HCOONa) 0,24 M jika diketahui Kb HCOO- = 5,9 x 10-11 Hitunglah pH dari larutan NH4Cl 0,42 M (Ka NH4+ =5,6 x 10-10)

Definition of An Acid _____________ is a substance that produces H+ (H3O+) in water A __________________ __________ is a proton donor A __________ is a substance that can accept a pair of electrons A __________ is a substance that can donate a pair of electrons + OH- • H O H • H+ acid base N H • H N H H H+ + acid base 16.12

Are any protons donated or accepted? Lewis Acids and Bases F B F N H • H F B F N H H + Which is the acid? Which is the base? Are any protons donated or accepted? 16.12