Exp. 6 Spectrophotometric Determination

• To perform a total iron measurement, it is essential to reduce any Fe3+ in solution to Fe2+ before adding the phenanthroline to form the complex
• reducing agent in this experimental protocol is hydroxylamine hydrochloride, which reacts with Fe3+ by this reaction

  A) 2Fe^3+

  B) 2NH3OH+(aq)

  C) 2Fe^2+(aq)

  D) N2(g)

  E) 2H2O(l)

  F) 4H+(aq)

  
• adding the phenanthroline, Reaction

  A) Fe^2+

  B) 3phen

  C) [Fe(phen)3]^2+

  
• Beer’s Law is used to determine the concentration of an unknown
• Beer's Law

  A = the absorbance from spectrophotometer

  ε = the extinction coefficient

  b = the pathlength of the cuvette (1 cm)

  c = the concentration of the solution in mol/L (mol∙L-1 )

  A) A

  B) E

  C) b

  D) c

  
• For beer's law plot the absorbance of each solution on the y-axis against its respective concentration on the x-axis
• Ligand that use to coordinate to from the iron complex is 1,10-phenanthroline.
• We plot absorbance and concentration for Beer's law plot.
• Sodium hydroxide is not use in the experiment.
• The technique used to determine the trace amount of iron solution is Spectrophotometric determination
• Oxidation State

  $Fe^+$$2$= Ferrous ion

  $Fe^+$$3$= Ferric ion
• The general principle of spectrophotometry used in this experiment is absorption of light by analytes.