Ainun dan winda
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Ainun dan winda

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    Ainun dan winda Ainun dan winda Presentation Transcript

    • By : Ainun Jariah Winda Hayati
    • * For centuries people had known that vinegar, lemonjuice,apple and many other food items taste sour. But they didn’tknow that their sourness comes from their specific acids. The termacid comes from the Latin word “acere” ,which means sour. In the17thcentury,the English Chemist Robert Boyle grouped substances aseither acids or bases, but he couldn’t explain their behavior. Thefirst logical definition wouldn’t be coined until 200 years later. In this presentation ,we will focus on acid-base reactions inaqueous solutions. such solutions play important roles in our dailylives. The Authors SupplementaryIntroduction Contents Material Questions Glossary References
    • Content 1. Acid-Base Theories 1.a. The Arrhenius Acid-Base Theory 1.b. The BrФnsted-Lowry Acid-Base Theory 1.c. The Lewis Theory 1.d. General Properties of Acids 1.e. General Properties of Bases 2. Ionization of Water 3. The pH Scale 4. Strength of Acids and Bases 4.a. Acid Strength 4.b. Base Strength 5. Neutralization SupplementaryIntroduction Contents Material Questions Glossary References
    • 1. Acid-Base Theories 1.a. The Arrhenius Acid-Base Theory In 1884, Swedish chemist Svante Arrhenius defined acids as compounds that produce H+ ions in aqueous solutions,and base as compounds that produce OH-- ions in aqueous solutions. For example,HCL and are HNO3 Arrhenius acids. HCL(aq) ------------→ Cl - (aq) + H+ (aq) HNO3 (aq) ---------- → NO 3- (aq) + H+ (aq) SupplementaryIntroduction Contents Material Questions Glossary References
    • 1. Acid-Base Theories NaOH and Ba(OH)2 are example of Arrhenius bases. These bases release OH-- ions in aqueous media. NaOH(aq) ------------→ Na +(aq) + OH - (aq) Ba(OH)2 (aq) ----------→ Ba 2+(aq) + 2OH - (aq) In water, the H+ ion of acid is attracted to a water(H2O) molecule to produce hydronium ion (H3O+ ) SupplementaryIntroduction Contents Material Questions Glossary References
    • 1. Acid-Base Theories • The Arrhenius acid-base theory is insufficient to explain the acidic or basic properties of some substances,such as SO2 and NH3 since these don’t have H + and OH- ions in their structures. For these molecules,another theory must be applied,since the Arrhenius acid-base theory can only be applied to aqueous solutions. SupplementaryIntroduction Contents Material Questions Glossary References
    • 1.Acid-Base Theories1.b. The The BrФnsted-Lowry Acid-Base Theory In 1923,Johannes BrФnsted and his English counterpart Thomas Lowry independently developed a more general acid-base theory. According to the BrФnsted-Lowry model,an acid is a proton donor and a base is a proton acceptor. Each proton donor(acid) has its pair(conjugate) proton acceptor base.For example: Conjugate acid- base pair NH3 H2O NH4+ OH- (Base 1) (Acid 2) (Acid 1) (Base 2) Conjugate acid- base pair Supplementary Introduction Contents Material Questions Glossary References
    • ExampleH2S (g) + H2O (l) ↔ H3O+ (aq) + HS- (aq)find the conjugate acid-base pairs for the abovereaction.Solution:H2S give H+ (proton) to H2O (proton accceptor), so itis an acid. In the same way, H2O accepts one H+(proton) from H2S (proton donor). Thus it is abase. Supplementary Introduction Contents Material Questions Glossary References
    • Example conjugate acid-base pairH2S (g) + H2O (l) ↔ H3O+ (aq) + HS- (aq)acid 1 base 2 acid 2 base 1 conjugate acid-base pair Supplementary Introduction Contents Material Questions Glossary References
    • 1.Acid-Base Theories NH3 and NH4+ form a conjugate acid-base pair,where NH3 is the conjugate base of NH4 (NH4+ is the conjugate acid of NH3). Similarly, H2O and OH- are conjugates of each other.A model of Acid-Base reaction between NH3 and H2O H N O N O H H H H H H H H H Supplementary Introduction Contents Material Questions Glossary References
    • 1.Acid-Base Theories 1.c. The Lewis Acid-Base Theory in 1923, American chemist,Gilbert N.Lewis definited acid and base considered to chemical bond theory. According to Lewis opinion that acid is compound that accept the pair of free electron. And base is compound that donor the pair of free electron. the example of The Lewis Acid-Base theory: F F B F F B F F F F SupplementaryIntroduction Contents Material Questions Glossary References
    • 1.Acid-Base Theories1.d. General Properties of Acids The General properties of Acids can be summarized as:1.The aqueous solutions of acids conduct electricity2. Acids change the color of litmus paper to red3. Acids have a sour taste (such as vinegar and lemon)4. Acids are corrosive substances.5. Acids react with active metals and produce hydrogen gas.For example:2Al(s) + 3H2SO4(aq) → Al2(SO4)3 (aq) + 3H2(g)Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2 (g) Supplementary Introduction Contents Material Questions Glossary References
    • 6. Acids react with bases to produce salt and water,this reaction is called a neutralization reaction.For example:NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)7.Inert metals (Cu,Hg,Ag,Pt,Au) do not react with binary acids(HCl,HBr,…). Cu,Hg,and Ag can react with strongoxyacid such as HNO3 and H2SO4.For example:3Cu(s) + 8HNO3(aq) →(dilute) → 3Cu(NO3)2 (aq) + 2NO (g) + 4H2O(l)8. Acids react with carbonate salts of metal.For example:MgCO3(s) + 2HCl(aq) → MgCl2(aq) + CO2(g) + H2O(l) Supplementary Introduction Contents Material Questions Glossary References
    • 1.Acid-Base Theories1.e. General Properties of BasesThe General properties of Bases can be summarized as:1.The aqueous solutions of Bases conduct electricity2. Bases change the color of litmus paper to blue3. Bases have a bitter taste4. Strong bases are corrosive5. Basic solutions cause slippery skin6. Bases do not react with most metals. However, strong bases(KOH,NaOH) react with amphoteric metals such as aluminium(Al), zink(Zn),and produce hydrogen gas.For example:2Al(s) + 6NaOH(aq) → 2Na3AlO3(aq) + H2(g)Zn(s) + 2NaOH(aq) → Na2ZnO2(aq) + H2 (g) Supplementary Introduction Contents Material Questions Glossary References
    • 2. Ionization of Water Some molecules and ions act as acids or bases depending on the conditions of the reaction are called amphoteric. A water molecule acts as an acid when it donates a proton, and acts as a base when it accepts a proton, as given below: H2O(l) +H2O(l) ↔ H3O+(aq) + OH-(aq) H O O O O H H H H H H H SupplementaryIntroduction Contents Material Questions Glossary References
    • 2. Ionization of Water The equilibrium sconstan expression for the reaction is: Kw = [H3O+ ] [OH-]Kw is the equilibrium constant used in equations to refer to ionization of water.Kw= 1,0 . 10-14 at 250C[H3O+ ] = [OH-] for the neutral medium. Then,1 . 10-14 = [H3O+ ] 2 1. 10-7 = [H3O+ ][H3O+ ] = [OH-] = 1. 10-7 M Supplementary Introduction Contents Material Questions Glossary References
    • 3. The pH ScaleThe acidity or basicity of a solution can be described in terms of its H3O+ or OH- ion concentrations.These concentrations are usually small. For example,H3O+ ion concentration is 1.10-7 M in the neutral solution. Thus,the concentration of H3O+ is generally expressed as the negative logarithm. This is known as pH. From now on, for simplicity H+ will be used instead of H3O+ pH = -log [H+] and [H+] = 10-pHIn a similar,the way negative logarithm of [OH-] is pOH pOH= -log[OH-] and [OH-] = 10-pOH Supplementary Introduction Contents Material Questions Glossary References
    • For pure water at 250C, [H+] = 1. 10-7 [OH-] = 1. 10-7 pH = - log (1. 10-7) pOH = - log (1. 10-7) pH = 7 pOH = 7Since [H+] [OH-] = 1. 10-14 a pH + pOH = 14The pH value of a solution gives an idea about the condition of a solution as follows: If pH < 7,0 Solution is acidic If pH = 7,0 solution is neutral If pH > 7,0 Solution is basic Supplementary Introduction Contents Material Questions Glossary References
    • pH is measured by using a pH meter. A pH meter translates H+ion concentrations in solutioninto an electrical signal that is converted into a digital display H+ CONCENTRATION, [H+] in mol/L100 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10-11 10-12 10-13 10-140 1 2 3 4 5 6 7 8 9 10 11 12 13 14 pH scale pure water baking powderAcid in stomach vinegar coffe rain water blood soap household lemon juice tomato bread milk sea water amonnia juice Supplementary Introduction Contents Material Questions Glossary References
    • A less accurate way to mesure pH is to use indicators. An indicator is a compound such as phenolphthalein or methyl orange, that is changes color reversibility at different pH values. For exampe, phenolphthalein is a colourless substance in any solution with a pH value smaller than 8,3 it turns red-violet in solution with a pH value greater than 8,3. Indicator Acidic Basic Phenolphthalein Colorless Red-violet Methyl orange Red Orange-yellow Litmus Red Blue SupplementaryIntroduction Contents Material Questions Glossary References
    • Example SupplementaryIntroduction Contents Material Questions Glossary References
    • Example SupplementaryIntroduction Contents Material Questions Glossary References
    • 4. Strength of Acids and Bases4.a. Acid Strength Acids are classified as strong and weak, depending upon theirdegree of ionization in water. A weak acidionizes in water reversibly to form H3O+ions. A weak acid is a weak electrolyte and its aqueous solution does not conduct electricity well. The dissociation reaction occurs to very small extent; usually,fewer than 1 percent of the HA molecules are ionized. The ionized of a weak acid is shown as follows: HA(aq) + H2O(l) ↔H3O+(aq) + A-(aq) weak acid conjugate base The dissociation constant Ka,of a given acid iswritten as ; Ka=[H3O+] [A-] / [HA] Ka refers to the acid dissociation constant which is measure of an acid’s strength. Some references call Ka the acid ionization constantIf Ka < 10-3, acid is generally said to be weakIf Ka = 1 to 10-3, acid is accepted as moderateIf Ka > 1 acid is strong. Supplementary Introduction Contents Material Questions Glossary References
    • Some Ka values of acids are given in Table below. Name of acid Formula Ka Hydrochloric acid HCL 1.107 Nitric acid HNO3 1.103 Sulfuric acid H2SO4 22 Oxalic acid (COOH)2 6,5 .10-2 Phosphoric acid H3PO4 7,5 . 10-3 Lictic acid C2H5OCOOH 1,38 .10-4 Formic acid HCOOH 1,8.10-4 Nitrous acid HNO2 4. 10-4 Hydroflouric acid HF 7,2 .10-4 Acetic acid CH3COOH 1,8 . 10-5 Supplementary Introduction Contents Material Questions Glossary References
    • 4. Strength of Acids and Bases4.2 Base StrengthThe dissociation of a weak base in water is illustrated as follows ; B(aq) + H2O(l)↔ BH+(aq) + OH-(aq)The equilibrium expression for the above weak base is Kb= [BH+] [OH-] / [B] Kb is the base dissociation constant or base ionization constant, that measure a base’s strength. Supplementary Introduction Contents Material Questions Glossary References
    • Some Kb values of bases are given in Tablebelow. Name of base Formula Kb Potassium hydroxide KOH 158,5 Sodium hydroxide NaOH 10 Methylamine CH3NH2 4,38 . 10-4 Ethylamine C2H5NH2 5,6 . 10-4 Ammonia NH3 1,8 . 10-5 Pyridine C5H5N 1,7 . 10-9 Aniline C6H5NH2 3,8 . 10-10 SupplementaryIntroduction Contents Material Questions Glossary References
    • Example SupplementaryIntroduction Contents Material Questions Glossary References
    • Example SupplementaryIntroduction Contents Material Questions Glossary References
    • 4. Strength of Acids and Bases4.c. Relationship between Ka and KbDissociation constants of weak acids and basescan be determined in the laboratory. However, itis easy to find the Ka or Kb values of acids orbases by using a simple mathematicalexpression between Ka and Kb of conjugate acid-base. The multiplication of Ka and Kb ofconjugate acid-base is Kw. Supplementary Introduction Contents Material Questions Glossary References
    • 4. Strength of Acids and BasesKw = Ka . Kb = Kb . Ka = 1 . 10-14For example NH4+ - NH3 is a conjugate acid base.I. NH3 + H2O ↔ NH4+ + OH- K1 = Kb of NH3II. NH4+ + H2O ↔ NH3 + H3O+ K2 = Ka of NH4+ 2H2O ↔ H3O+ + OH- Kw = K1 . K2 Supplementary Introduction Contents Material Questions Glossary References
    • ExampleWhat is the Ka value of NH4+ if the Kb of NH3 is1.8 x 10-5 ?Solution:NH3 + H2O ↔ NH4+ + OH-NH4+ is the conjugate acid of NH3Kb for NH3 is 1,8 x 10-5 Supplementary Introduction Contents Material Questions Glossary References
    • Example SupplementaryIntroduction Contents Material Questions Glossary References
    • 5. Neutralization The reaction of an acid and a base solution to form salt and water is called a neutralization reaction. Indeed,a neutralization reaction is a reaction hydrogen(H+) ions and hydroxide(OH-) ions to form water. In neutralization,all H+ and OH- ions coming from acid and bases turn into H2O. The reaction between HCl(aq) and NaOH(aq) is an example of a neutralization reaction. HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l) The net ionic equation for this reaction is H+(aq) + OH- (aq)→ H2O (l) SupplementaryIntroduction Contents Material Questions Glossary References
    • The nature of the particular acid and base involved in a reaction determines the acidity or basicity of the resulting solution.1 .Neutralization of a strong acid and strong base gives a neutral solution.HCl(aq) + NaOH(aq) → NaCl(aq) + H2O(l)The resulting NaCl salt is neutral2. Neutralization of a strong acid and a weak base gives a acidic solution.HCl(aq) + NH3(aq) → NH4Cl(aq) + H2O(l)NH4Cl is called acidic salt3. Neutralization of a weak acid and a strong base gives a basic solution.CH3COOH(aq) + NaOH(aq) → CH3COONa(aq) + H2O(l)CH3COONa is called basic salt4. Neutralization of a weak acid and a weak base gives a complex type of acid-base solution. If weak acid and weak base have the same strength,the solution is neutral. If the strength of an acid and base are not equal,the solution will be either acidic or basic,depending on the strength of either. Supplementary Introduction Contents Material Questions Glossary References
    • Supplementary Questions1. Find the conjugate acid-base pairs for the following reaction. a. CO32- + H2O ↔ HCO3- + OH- b. HF + H2O ↔ H3O+ + F- c. NH3 + H2O ↔ NH4+ + OH- d. HSO4- + HCl ↔ H2SO4 + Cl- Supplementary Introduction Contents Material Questions Glossary References
    • Supplementary Questions2. What is the pH of a solution prepared by dissolving 0.8 g NaOH in water to make 200 mL solution ?3. How many moles of HCl are found in 500 mL of HCl solution, whit a pH of 3 ?4. How many millilitres of 0.01 M NaOH are required to neutralize 50 mL of 0.02 M HCl ? Supplementary Introduction Contents Material Questions Glossary References
    • Supplementary Questions5. I II after mixing the solutions, what would be the pH of the final solution ? Supplementary Introduction Contents Material Questions Glossary References
    • GlossaryAcid : A substance that produces hydrogen ionsin solution. A proton donor substance.Acid dissociation constans (Ka) : The equilibriumconstant for weak acids.Aqueous solutions : solutions in which water isthe solvent.Arrhenius concept : A concept stating that acidsproduce hydrogen ions and bases produchydroxide ions in aqueous solution. SupplementaryIntroduction Contents Material Questions Glossary References
    • GlossaryBase : A substance that produces hydroxide ionsin aqueous solution. A proton acceptor substanceBase dissociation constans (Kb) : the equilibriumconstans for the reaction of a base with water toproduce the conjugate acid and hydroxide ion.Chemical bond : The force, or energy, that holdsatoms together in a compound. Supplementary Introduction Contents Material Questions Glossary References
    • GlossaryConjugate acid : The specie formed when aproton is added to a base.Conjugat acid-base pair : two species related toeach other by donating and accepting of a singleproton.Conjugat base : What remains of an acidmolecule after a proton is lost. Supplementary Introduction Contents Material Questions Glossary References
    • GlossaryEquilibrium : The position where the rate offorwad and reverse reaction becomes equal.Indicator : A chemical that changes color and isused to mark the end-point of a titration.Ion-product constant (Kw) : the equilibriumconstant for water.Lewis acid : An electron-pair acceptor Supplementary Introduction Contents Material Questions Glossary References
    • Glossary SupplementaryIntroduction Contents Material Questions Glossary References
    • GlossaryPolyprotic acid : an acid with more than oneacidic proton. It dissociates in a stepwisemanner, one proton at a time.Salt brige : A U-shaped tube containing anelectrolyte that connects the two compartmentsof a galvanic cell without extensive mixing of thedifferent solutions. Supplementary Introduction Contents Material Questions Glossary References
    • GlossarySolution : A homogeneous mixture.Strong base : A metal hydroxide salt thatcompletely dissociates into its ions in water.Weak acid : An acid that dissociates only slightlyin aqueous solution.Weak base : A base that reacts with water toproduce hydroxide ions to only a slight extentain aqueous solution. Supplementary Introduction Contents Material Questions Glossary References
    • References• Nazli, Ayhan., Lise 2 kimya Ders Kitab. Textbook of Chemistry for Lycee 2. Zambak Publishing, Istanbul : 2006• McDuell B., A Level Chemistry. Letts Education, UK : 2000• Earl B., Wilford L.D.R., IGCSE Chemistry. Hodder Murray, Dubai : 2005 Supplementary Introduction Contents Material Questions Glossary References
    • References• Ratcliff B., Eccles H., and others, AS Level and A level Chemistry. Cambridge University Press, UK : 2005• Oxtoby, D.W., Nachtrieb, N.H., Principals of Modern Chemistry. 3rd Ed., Saunders Collage Publising, USA : 1996 Supplementary Introduction Contents Material Questions Glossary References
    • References• Sevenair, J.P., Burkett, A.R., Introductory Chemistry. Investigating the Molecular Nature of Matter. WBC Publishers, USA :1997• Prescott, C.N., Chemistry A Course for “0” Level. Times Media Privat Limited, Singapore : 2000 Supplementary Introduction Contents Material Questions Glossary References