Titrasi Pengendapan (Metode Mohr)

Menentukan konsentrasi klorida menggunakan perak nitrat

Titrations Advanced (University) 45 menit ~$20,00

Tujuan

Tentukan konsentrasi ion klorida dalam larutan menggunakan metode Mohr, di mana perak nitrat adalah titran dan kalium kromat adalah indikatornya.

Latar Belakang

In the Mohr method, silver nitrate reacts with chloride ions to form white silver chloride precipitate. When all chloride is consumed, the first excess silver reacts with the chromate indicator to form brick-red silver chromate, signaling the endpoint. This method works at near-neutral pH.

Peringatan Keselamatan

  • Silver nitrate stains skin and clothing permanently
  • Potassium chromate is toxic and a suspected carcinogen — handle with extreme care
  • Wear nitrile gloves and safety goggles
  • Dispose of silver and chromate waste in designated containers

APD yang Diperlukan

goggles gloves lab_coat

Bahan

  • Sodium chloride solution (100 mL)
    Unknown concentration
  • Silver nitrate (AgNO₃) (100 mL)
    0.1M standardized
  • Potassium chromate (K₂CrO₄) (10 mL)
    5% indicator solution
  • Distilled water (200 mL)

Peralatan

50 mL burette Burette stand and clamp 250 mL Erlenmeyer flask 25 mL pipette White tile

Prosedur

1

Pipette 25.0 mL of the chloride solution into the Erlenmeyer flask.

2 menit
2

Add 1 mL of 5% potassium chromate indicator. The solution turns pale yellow.

1 menit Chromate is toxic — use minimal amount
3

Fill the burette with 0.1M AgNO₃. Record the initial volume.

3 menit AgNO₃ stains permanently
4

Titrate while swirling vigorously. A white precipitate of AgCl forms.

10 menit
5

Near the endpoint, the precipitate becomes more curd-like. Add AgNO₃ drop by drop until a permanent brick-red color of Ag₂CrO₄ appears.

5 menit
6

Record the volume. Repeat for concordant results.

15 menit
7

Calculate chloride concentration: C(Cl⁻) = C(Ag+) x V(AgNO₃) / V(sample).

5 menit

Hasil yang Diharapkan

The endpoint is marked by the first permanent appearance of a brick-red color due to Ag₂CrO₄ formation. This color should persist for at least 30 seconds after swirling.

Pembersihan

Collect all silver-containing waste in the designated heavy metal waste container. Collect chromate waste separately. Never dispose down the drain. Wash hands thoroughly.

Detail

Kategori
Titrations
Tingkat Kesulitan
Advanced (University)
Durasi
45 menit
Perkiraan Biaya
$20,00
Langkah
7
Bahan
4

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Frequently Asked Questions

What is the objective of Titrasi Pengendapan (Metode Mohr)?
Tentukan konsentrasi ion klorida dalam larutan menggunakan metode Mohr, di mana perak nitrat adalah titran dan kalium kromat adalah indikatornya.
How difficult is Titrasi Pengendapan (Metode Mohr)?
This experiment is rated as Advanced (University). It takes approximately 45 minutes to complete.
What safety precautions are needed for Titrasi Pengendapan (Metode Mohr)?
Key safety precautions include: Silver nitrate stains skin and clothing permanently; Potassium chromate is toxic and a suspected carcinogen — handle with extreme care; Wear nitrile gloves and safety goggles.
What materials are needed for Titrasi Pengendapan (Metode Mohr)?
The main materials required are: Sodium chloride solution, Silver nitrate (AgNO₃), Potassium chromate (K₂CrO₄), Distilled water.
What results should I expect from Titrasi Pengendapan (Metode Mohr)?
The endpoint is marked by the first permanent appearance of a brick-red color due to Ag₂CrO₄ formation. This color should persist for at least 30 seconds after swirling.