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Buffer solutions

Buffer solutions. Conjugate Acid and Base. Conjugate acid and base , HA/A - , differ by one proton. The conjugate acid of a base, is the base plus the attached proton. And the conjugate base of an acid is the acid minus the proton. Example:. Acid And Base Ionization Constants.

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Buffer solutions

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  1. Buffer solutions

  2. Conjugate Acid and Base • Conjugate acid and base, HA/A-, differ by one proton. • The conjugate acid of a base, is the base plus the attached proton. • And the conjugate base of an acid is the acid minus the proton. Example:

  3. Acid And Base Ionization Constants weak acid: CH3COOH + H2O ↔ H3O+ + CH3COO- [H3O+][CH3COO-] Acid ionization constant: Ka= [CH3COOH] weak base: NH3 + H2O ↔ NH4+ + OH- [NH4+][OH-] Base ionization constant: Kb= [NH3] Acid and base ionization constants are the measure of the strengths of acids and bases.

  4. pKa and pKb pKa = -logKa pKb = -logKb larger Ka→ smaller pKa→ stronger acid larger Kb→ smaller pKb→ stronger base

  5. Henderson-Hasselbalch Equation [conjugate base] pH = pKa + log [weak acid] If: [weak acid] = [conjugate base], then: pH = pKa

  6. Buffers • A buffer is a solution characterised by the ability to resist changes in pH when limited amounts of acid or base are added to it. • Buffers contain either a weak acid and its conjugate base or a weak base and its conjugate acid. • Thus, a buffer solution contains both an acid species and a base species in equilibrium.

  7. Example of weak acid/conjugate base as buffer system: • HC2H3O2 + C2H3O2- • How does this work? • What happens when H+ is added? • What happens when OH- is added?

  8. How A Buffer Solution Works • The acid component of the buffer can neutralize small added amounts of OH-, and the basic component can neutralize small added amounts of H3O+. • The result is just more weak acid or more weak base in the system.

  9. Acetic Acid/Acetate Buffer

  10. Buffer resist change in pH

  11. Buffer Capacity And Buffer Range • There is a limit to the capacity of a buffer solution to neutralize added acid or base, and this limit is reached before all of one of the buffer components has been consumed. • In general, the more concentrated the buffer components in a solution, the more added acid or base the solution can neutralize. • As a rule, a buffer is most effective if the concentrations of the buffer acid and its conjugate base are equal. • Buffers are effective around pH values that are equal to the pKa ±1.

  12. Power of Buffering Action

  13. Buffers • summary: • consist of • Weak acid and its salt • Weak base and its salt • or • and • resist changes in pH • to • Maintain pH balance • preventing • Acidosis • and • Alkalosis

  14. وحــشـــــوت أحـشـــــــــائـــي بـخـالــــص حــبـه بـشــــــــراك أحـشـــــــــائـــي بــه بـشـــــــــراك

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