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Lecture 8

Lecture 8. Titrations - II. Conc. H 2 SO 4 + catalyst. >300 o C. All N  NH 4 +. C CO 2. Kjeldahl digestion. H H 2 O. NH 3 + H + NH 4 +. NH 3 +H 2 O. If HCl:. Excess of H + can be titrated with NaOH. NaOH+NH 3. If boric acid:. HCl or H 3 BO 3.

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Lecture 8

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  1. Lecture 8 Titrations -II

  2. Conc. H2SO4 + catalyst >300o C All N NH4+ CCO2 Kjeldahl digestion HH2O

  3. NH3+ H+NH4+ NH3+H2O If HCl: Excess of H+ can be titrated with NaOH NaOH+NH3 If boric acid: HCl or H3BO3 B(OH)4- + H+ H3BO3 + H2O

  4. Precipitation Titration AgNO3 + NaCl  AgCl + NaNO3 Ag+ + Cl- AgCl

  5. AgCl  Ag+ + Cl- KSP = [Ag+][Cl-] pX = - log10[X] pAg = - log10[Ag+]

  6. Na+ Na+ NO3- NO3- Cl- n- Cl- Na+ Na+ Cl- Cl- NO3- AgNO3 AgNO3 AgCl Cl- AgCl Cl- Cl- Cl- Na+ Na+ Na+ soluble Na+ NO3- Colloid equivalence point: coagulation In the middle @ first drops no chloride ion left in solution, no further precipitation possible

  7. Titration of NaCl with AgNO3 C=0.1 M [Cl-]=10-4 M [Ag+]=1.810-6 M 99.9% Ag+ Equivalence point [Ag+]=[Cl-] Acceptable end point 100.1% Ag+ [Ag+]=10-4 M

  8. I- + Ag+  AgI pAg= -log[Ag+] 99.9% Ag+ Ksp(AgI)=[Ag+][I-]=8.310-17 Acceptable end point 100.1% Ag+

  9. Precipitation titration with silver electrode The change of Vis proportional to pAg V(mV)

  10. I- I- Ind2- _ _ _ _ _ _ _ I- _ I- Ind2- Ind2- Ag+ Ag+ + + + + Ind2- + + + + Ag+ + Ag+

  11. Precipitation Titrations:

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