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CI 8.1 Acids and Bases

CI 8.1 Acids and Bases. Acids. Turn litmus red Neutralised by bases pH < 7 Liberate CO 2 from carbonates. Br Ø nsted-Lowry Theory. An acid is an H + donor A base is an H + acceptor H + Cl - + NH 3  Cl - + NH 4 +. The oxonium ion.

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CI 8.1 Acids and Bases

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  1. CI 8.1AcidsandBases

  2. Acids • Turn litmus red • Neutralised by bases • pH < 7 • Liberate CO2 from carbonates

  3. BrØnsted-Lowry Theory • An acid is an H+ donor • A base is an H+ acceptor • H+Cl- + NH3 Cl- + NH4+

  4. The oxonium ion • An acid reacts with water to form oxonium ions • HCl + H2O  H3O+ + Cl- • Water is acting as a base

  5. The oxonium ion H H+ x O x What type of bond is this? H

  6. A base is a substance which accepts H+ ions Alkali = a base which forms OH- ions in water Is there a difference between an alkali and a base?

  7. How are hydroxide ions (OH-) made? • NaOH Na+ + OH- • CO32- + H2O HCO3- + OH- • NH3 + H2O NH4+ + OH-

  8. Acid – base pairs • CH3COOH CH3COO- + H+ • CH3COO- + H+ CH3COOHThe ethanoate ion can behave as a base; it is the conjugate base of ethanoic acid. • HA H+ + A- Conjugate base Conjugate acid

  9. Every acid has a conjugate base • Every base has a conjugateacid

  10. Amphoteric substances • Water can act as either an acid or a base • With a strong acid it acts as a base • With a strong base it acts as an acid • A substance which behaves in this way is said to be amphoteric

  11. Water as an amphoteric substance • Water in the presence of a strong acid:H3O+ H+ + H2O • Water in the presence of a strong base:H2O H+ + OH-

  12. Strength of acids and bases • A strong acid is a powerful H+ donor; it is fully dissociated • A weak acid is a moderate or weak H+ donor; it is weakly dissociated • A strong acid has a weak conjugate base and vice versa

  13. Which is the acid form? Indicators • Coloured organic substances • Weak acids • Conjugate acid and conjugate base forms are different colours • e.g. litmus:HIn H+ + In-red blue

  14. What is the equation for addition of alkali? Addition of acid • In- + H3O+HIn + H2O • The blue litmus turns red

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