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BUFFERS AND pH

BUFFERS AND pH. Buffers are solutions which have the ability to resist changes in acidity and alkalinity. Acid buffers and basic buffers are two types of synthetic buffers that are produced in the lab. Acid buffers keep the pH blow 7. Alkaline buffers keep the pH above 7.

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BUFFERS AND pH

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  1. BUFFERS AND pH Yogini D. Lall

  2. Buffers are solutions which have the ability to resist changes in acidity and alkalinity. Yogini D. Lall

  3. Acid buffers and basic buffers are two types of synthetic buffers that are produced in the lab. Yogini D. Lall

  4. Acid buffers keep the pH blow 7 Yogini D. Lall

  5. Alkaline buffers keep the pH above 7. Yogini D. Lall

  6. ACID BUFFER SOLUTIONSweak acid – ethanoic acid, CH3COOHsalt of acid – sodium ethanoateCH3COOHNa Yogini D. Lall

  7. Partial dissociation into ions:CH3COOH(aq) CH3COO-(aq) + H+ (aq) (A)Complete dissociation unit ions:CH3COOHNa(aq) CH3COO-(aq) + H+ (aq) (B) Yogini D. Lall

  8. Adding AlkaliOH- (aq)+ H+ (aq) H2O (l)The OH- (aq)will remove the H+ (aq) ions and shift equilibrium to the right. This will regenerate more hydrogen to react with further hydroxide. The hydroxide is therefore “mopped up” by the hydrogen ions. In this way pH does not change. Yogini D. Lall

  9. Adding AcidCH3COO + H+ CH3COOHThis time the buffer has to mop up extra hydrogen ions from the acid. Equilibrium shifts to the left, removing the majority of the added hydrogen ions by the ethanoate ions keeping the pH approximately constant. Yogini D. Lall

  10. ALKALINE BUFFER SOLUTIONSWeak alkali: Ammonium hydroxide NH3OHSalt of alkali: Ammonium chloride, NH3Cl Yogini D. Lall

  11. Partial dissociation into ions:NH3(aq) + H2O(l) NH 4+(aq) + OH -(aq)ion in solution, most of NH3 is solvated by water only a few reacts with water. Yogini D. Lall

  12. Compete dissociation:NH4Cl(aq) NH 4+(aq)Cl- (aq) Yogini D. Lall

  13. ADDING ACIDHydrogen ions will be mopped up by hydroxide ion shifting equilibrium to the right causing the pH to remain constant. Yogini D. Lall

  14. ADDING ALKALIHydroxide ions are mopped up by ammonium ions and thus causing the pH to remain constant. Yogini D. Lall

  15. BUFFERS IN BIOLOGICAL SYSTEMS.Cell contents are buffered to provide a suitable pH by a) phosphatesb) hydrogen carbonatec) amino acid, peptides and proteins. Yogini D. Lall

  16. All chemical reactions are enzyme dependent and enzymes can only function at a pH range of 2 units (2-3 pH units) say pH 7.Buffers are also important in industries e.g. Medicines and cosmetics. Yogini D. Lall

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