Determinação de Ferro na Água

Medição da concentração de ferro dissolvido usando colorimetria de tiocianato

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

Objetivo

Determinar a concentração de ferro(III) em uma amostra de água usando o método colorimétrico do tiocianato.

Contexto

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.

Avisos de segurança

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

EPI necessário

goggles gloves lab_coat

Materiais

  • 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

Equipamentos

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

Procedimento

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.

Limpeza

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

Detalhes

Categoria
Colorimetry
Dificuldade
Intermediate (High School)
Duração
75 min
Custo estimado
$10,00
Passos
7
Materiais
5

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Frequently Asked Questions

What is the objective of Determinação de Ferro na Água?
Determinar a concentração de ferro(III) em uma amostra de água usando o método colorimétrico do tiocianato.
How difficult is Determinação de Ferro na Água?
This experiment is rated as Intermediate (High School). It takes approximately 75 minutes to complete.
What safety precautions are needed for Determinação de Ferro na Água?
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 Determinação de Ferro na Água?
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 Determinação de Ferro na Água?
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.