Rekristalisasi Asam Benzoat

Memurnikan padatan dengan melarutkan dalam pelarut panas dan mendinginkan

Crystallization Intermediate (High School) 45 menit ~$10,00

Tujuan

Murnikan asam benzoat tidak murni dengan rekristalisasi dari air panas, mendemonstrasikan teknik pemurnian standar untuk padatan organik.

Latar Belakang

Recrystallization exploits the difference in solubility of a substance at different temperatures. Benzoic acid is very soluble in hot water but nearly insoluble in cold water. By dissolving impure benzoic acid in hot water and cooling slowly, pure crystals form while impurities remain in solution.

Peringatan Keselamatan

  • Handle hot water and hot glassware with care
  • Benzoic acid dust can irritate airways
  • Use heat-resistant gloves when handling hot flasks

APD yang Diperlukan

goggles lab_coat

Bahan

  • Impure benzoic acid (3 g)
    Mixed with charcoal or sand
  • Distilled water (200 mL)
  • Activated charcoal (0.5 g)
    Optional, for decolorization

Peralatan

250 mL Erlenmeyer flask Hot plate Buchner funnel Filter flask Vacuum pump Melting point apparatus Ice bath Watch glass

Prosedur

1

Weigh 3 g of impure benzoic acid and record the mass. Note the appearance (color, particle size).

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2

Add the impure sample to 100 mL of distilled water in the Erlenmeyer flask. Heat to boiling while stirring.

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3

If the solution is colored, add 0.5 g activated charcoal, swirl, and filter hot through fluted filter paper.

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4

Allow the clear filtrate to cool slowly to room temperature. Do not disturb.

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5

Cool further in an ice bath to maximize crystal yield.

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6

Collect the crystals by vacuum filtration. Wash with a small amount of ice-cold water.

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7

Dry the crystals on a watch glass. Weigh and calculate percent recovery.

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8

Determine the melting point (pure benzoic acid: 122°C) and compare with the impure sample.

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Hasil yang Diharapkan

White, needle-like crystals with a sharp melting point at 121-123°C. Typical recovery is 60-80%. The purified crystals should be whiter and have a sharper melting point than the crude material.

Pembersihan

Dispose of filtrate down the drain (benzoic acid is food-grade). Rinse glassware. Dispose of charcoal in solid waste.

Detail

Kategori
Crystallization
Tingkat Kesulitan
Intermediate (High School)
Durasi
45 menit
Perkiraan Biaya
$10,00
Langkah
8
Bahan
3

Eksperimen Lainnya

Kristalisasi Fraksional Garam dan Pasir 35 min Kristalisasi Salol (Fenil Salisilat) 30 min Lewat Jenuh dan Kristalisasi Seketika 35 min Menumbuhkan Kristal Pelangi Bismut 45 min Menumbuhkan Kristal Tawas 30 min Menumbuhkan Kristal Tembaga Sulfat 30 min Permen Batu Kristal Gula 25 min

Frequently Asked Questions

What is the objective of Rekristalisasi Asam Benzoat?
Murnikan asam benzoat tidak murni dengan rekristalisasi dari air panas, mendemonstrasikan teknik pemurnian standar untuk padatan organik.
How difficult is Rekristalisasi Asam Benzoat?
This experiment is rated as Intermediate (High School). It takes approximately 45 minutes to complete.
What safety precautions are needed for Rekristalisasi Asam Benzoat?
Key safety precautions include: Handle hot water and hot glassware with care; Benzoic acid dust can irritate airways; Use heat-resistant gloves when handling hot flasks.
What materials are needed for Rekristalisasi Asam Benzoat?
The main materials required are: Impure benzoic acid, Distilled water, Activated charcoal.
What results should I expect from Rekristalisasi Asam Benzoat?
White, needle-like crystals with a sharp melting point at 121-123°C. Typical recovery is 60-80%. The purified crystals should be whiter and have a sharper melting point than the crude material.