Determinación de Hierro en Agua

Medición de la concentración de hierro disuelto usando colorimetría de tiocianato

Colorimetry Intermediate (High School) 75 min ~$10,00

Objetivo

Determinar la concentración de hierro(III) en una muestra de agua usando el método colorimétrico del tiocianato.

Antecedentes

Iron(III) ions react with thiocyanate ions (SCN⁻) to form the intensely red-colored complex [Fe(SCN)]²⁺. The intensity of the red color is proportional to the Fe³⁺ concentration, following the Beer-Lambert law. This method is widely used in water quality testing and environmental monitoring. Students learn both the analytical technique and the chemistry of complex ion formation.

Advertencias de seguridad

  • FeCl₃ solution stains skin and clothing
  • KSCN is harmful if swallowed
  • HNO₃ is corrosive — handle with care
  • Dispose of thiocyanate waste in designated containers

EPP requerido

goggles gloves lab_coat

Materiales

  • Iron(III) chloride (FeCl₃) standard (100 mL)
    0.01 M stock solution
  • Potassium thiocyanate (KSCN) (100 mL)
    0.1 M solution
  • Dilute HNO₃ (0.1 M) (50 mL)
    To maintain acidity
  • Water sample (50 mL)
    Unknown iron content
  • Distilled water (500 mL)
    For dilutions

Equipamiento

Colorimeter or spectrophotometer Cuvettes (matched pair) Volumetric flasks (50 mL, 7 total) Pipettes (1 mL, 5 mL, 10 mL) Pipette filler

Procedimiento

1

Prepare a series of standard Fe³⁺ solutions (0, 1, 2, 4, 6, 8, 10 ppm) by diluting the stock FeCl₃ solution in 50 mL volumetric flasks.

15 min
2

Add 5 mL of 0.1 M KSCN and 2 mL of dilute HNO₃ to each standard flask and the water sample. Make up to volume with distilled water.

10 min
3

Allow 5 minutes for full color development. The solutions should range from pale to deep red.

5 min
4

Set the colorimeter to 480 nm. Zero with the blank solution (0 ppm Fe³⁺ + KSCN).

5 min
5

Measure the absorbance of each standard solution and the water sample.

15 min
6

Plot the calibration curve (absorbance vs. concentration). Use it to determine the iron concentration in the water sample.

15 min
7

Calculate the iron concentration and evaluate whether the water meets drinking water standards (<0.3 ppm).

10 min

Resultados esperados

The calibration curve should be linear from 0 to 10 ppm. The deep red color of [Fe(SCN)]²⁺ intensifies with increasing Fe³⁺ concentration. The water sample's iron content is determined from the calibration curve.

Limpieza

Collect all thiocyanate-containing solutions in labeled waste. Rinse all glassware thoroughly. Wipe down the colorimeter.

Detalles

Categoría
Colorimetry
Dificultad
Intermediate (High School)
Duración
75 min
Costo estimado
$10,00
Pasos
7
Materiales
5

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Frequently Asked Questions

What is the objective of Determinación de Hierro en Agua?
Determinar la concentración de hierro(III) en una muestra de agua usando el método colorimétrico del tiocianato.
How difficult is Determinación de Hierro en Agua?
This experiment is rated as Intermediate (High School). It takes approximately 75 minutes to complete.
What safety precautions are needed for Determinación de Hierro en Agua?
Key safety precautions include: FeCl₃ solution stains skin and clothing; KSCN is harmful if swallowed; HNO₃ is corrosive — handle with care.
What materials are needed for Determinación de Hierro en Agua?
The main materials required are: Iron(III) chloride (FeCl₃) standard, Potassium thiocyanate (KSCN), Dilute HNO₃ (0.1 M), Water sample, Distilled water.
What results should I expect from Determinación de Hierro en Agua?
The calibration curve should be linear from 0 to 10 ppm. The deep red color of [Fe(SCN)]²⁺ intensifies with increasing Fe³⁺ concentration. The water sample's iron content is determined from the calibration curve.