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Acid base equilibrium

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  • 1. ACID BASE EQUILIBRIUM GROUP MEMBERS : NOOR AZURAH ABDUL RAZAK (D20101037502)SITI NORHAFIZA HAFINAS MOHD ZANUDIN (D20101037503)
  • 2. Ion Product constant Kw=[H†][OH⁻] =(1.0x10⁻⁷)(1.0x10⁻⁷) Theory = 1.0x10⁻ˡ⁴ Arheniuss Bronsted-Lowry pH = -log[H†] pOH = -log[OH⁻] ACID BASEhpH + pOH = 14.00 EQUIL RIUM IB Weak Acid Weak Base Strong Acid Strong Base HCN,H2S NH3 HCl, HBr NaOH  H+   A−   BH +   OH −  Ka =     Kb =    Ionize completely(100%) in [ HA ] [ B] water Dissociate partially in water
  • 3. ACID-BASE THEORY
  • 4. Arrhenius Theory• The concept began in 1887• Acid - a substance that, when dissolved in water, increases the concentration of H+ ions.• Base - a substance that, when dissolved in water, increases the concentration of OH- ions.• Disadvantage- Apply only to aqueous solution
  • 5. Bronsted-Lowry Theory In 1923, Johannes Bronsted and Thomas Lowry proposed a more general definition of acids bases Acid - a substance (molecule or ion) that donates a proton to another substanceBase - a substance that accepts a protonNot necessarily to be in aqueous solution
  • 6. ION PRODUCT OF WATER Ion-product of water refers to autoionization of water H₂O(l) ↔ H†(aq) + OH‾ (aq) The equilibrium constant for the autonization of wateris : Kw =[H†][OH‾ ]Kw is called ion-product constant, which is the product of the molar conentration of H† and OH‾ at a particular temperature
  • 7. In pure water at 25⁰c, [H†]=[OH⁻]=1.0x10⁻⁷ Kw =[H†][OH⁻] = (1.0x10⁻⁷)(1.0x10⁻⁷) = 1.0x10⁻ˡ⁴
  • 8. pH SCALE Use to measure the concentration of H† in a solution Measuring the acidity of the solution pH : negative base-10 log of the concentration of hydrogen oin, [H†] pH = -log[H†] pOH : negative base-10 log of the concentration of hydroxide oin, [OH⁻] pOH = -log[OH⁻] pH + pOH = 14.00
  • 9. Example :Given that the pH of hydrogen sulfide,H₂Sis 4.82. Find the concentration ofhydrogen ion, [H†]Solution : pH = -log[H†] 4.82 = -log[H†] [H†] = antilog (-4.82) = 1.51 x 10⁻⁵
  • 10. Strong acid WeakWeakacid Acid &Base base Strong base
  • 11. Strong acid + −HCl( aq ) + H 2O( l)     H 3O → 100%ionization ( aq ) + Cl ( aq )
  • 12. Strong bases• Dissociate completely in an aqueous solution to produce high concentration of OH-• 100% ionization or 100% dissociation• Example NaOH and KOH NaOH( aq )     Na + ( aq ) + OH − ( aq ) 100%ionization →
  • 13. Weak acidsCH 3 COOH ( aq ) + H 2 O ( l ) ⇔ CH 3 COO − ( aq ) + H 3 O + ( aq )
  • 14. Weak bases + −NH 3( aq ) + H 2 O ⇔ NH 4 ( aq ) + OH ( aq )
  • 15. ACIDS AND EQUILIBRIUM• Equilibrium constant can be used for the ionization reaction to express the extent to which a weak acids ionizes. HA( aq ) + H 2O( l ) ⇔ H 3O + ( aq ) + A− ( aq ) HA( aq ) ⇔ H + ( aq ) + A− ( aq ) Ka = [ H O ][ A ] 3 + − or Ka = [ H ][ A ] + − [ HA] [ HA]• A smaller Ka value meaning the degree of the dissociation of the acid is low
  • 16. BASES AND EQUILIBRIUM• the base is a weak base (ionizes <100%), the equilibrium is dependent on the base equilibrium constant, Kb.• A base equilibrium expression can only be written for weak bases. B( aq ) + H 2 O( l ) ⇔ BH + ( aq ) + OH − ( aq ) Kb = [ BH ][OH ] + − [ B]