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1 markFirst Row Transition Elements

CAPE Chemistry Unit 1 · 2005 · Paper 2 · Question 9(b)(iii)

Iron(II) concentration in water is determined spectrophotometrically at 510 nm by forming a complex with 1,10-phenanthroline.

Suggest why a wavelength of 510 nm is chosen for the spectrophotometric measurements.

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Other parts of this question

  1. 9(a)State the fundamental principles upon which ultraviolet/visible (UV/Vis) spectroscopy is based.[5 marks]
  2. 9(b)(i)State the observation when 1,10-phenanthroline is added to the reduced iron(II) solution.[1 mark]
  3. 9(b)(ii)Explain the properties of 1,10-phenanthroline that make it suitable for quantitative UV/Vis analysis of iron(II).[3 marks]
  4. 9(b)(iv)Describe the procedure for constructing a calibration curve for this spectrophotometric analysis.[3 marks]
  5. 9(c)(i)Calculate the molar concentration in mol dm^-3 of the standard iron(II) solution.[3 marks]
  6. 9(c)(ii)Use the Beer-Lambert law to calculate the molar absorptivity of the iron(II) complex.[3 marks]
  7. 9(c)(iii)Calculate the concentration of iron(II) in the unknown sample in mol dm^-3.[1 mark]

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