Reaktion von Natrium und Wasser

Beobachtung der heftigen Reaktion eines Alkalimetalls mit Wasser

Classroom Demonstrations Advanced (University) 25 Min. ~$12,00

Ziel

Die Reaktivität von Alkalimetallen demonstrieren, indem Natrium mit Wasser zur Reaktion gebracht und die Wasserstoffentwicklung sowie die Hydroxidbildung beobachtet wird.

Hintergrund

Sodium metal reacts vigorously with water in a classic demonstration of alkali metal reactivity: 2Na + 2H₂O → 2NaOH + H₂. The sodium skates across the water surface as hydrogen gas is evolved, often melting into a ball from the heat of reaction. Adding phenolphthalein indicator to the water reveals the spreading pink color of NaOH as it forms. This reaction illustrates metallic bonding (soft metal), oxidation states, and the trend of increasing reactivity down Group 1.

Sicherheitswarnungen

  • Sodium is highly reactive — NEVER handle with bare hands
  • Keep sodium away from water until ready for demonstration
  • Cut sodium on a dry tile; keep pieces small (pea-sized maximum)
  • Use safety shield between reaction and audience
  • Hydrogen gas is flammable — larger pieces may ignite the hydrogen
  • NaOH solution formed is corrosive
  • Never use pieces larger than a small pea for this demonstration

Erforderliche PSA

goggles gloves lab_coat face_shield

Materialien

  • Sodium metal (1 small piece)
    Pea-sized, stored under mineral oil
  • Phenolphthalein indicator (5 mL)
    Added to water
  • Distilled water (500 mL)
  • Mineral oil (For storage)

Ausrüstung

Large glass trough or crystallizing dish Safety shield Forceps Scalpel or knife (for cutting sodium) Filter paper Tile for cutting

Durchführung

1

Fill the trough with about 300 mL of water. Add a few drops of phenolphthalein indicator. Set up the safety shield.

3 Min.
2

Using forceps, remove a small piece of sodium from the mineral oil. Blot excess oil with filter paper on a dry tile.

2 Min. Keep all water away from cutting area
3

Cut a very small piece (no larger than a pea). Return the remainder to the mineral oil.

2 Min. Cut on dry surface only
4

Drop the sodium piece into the water from behind the safety shield. Step back immediately.

1 Min. STEP BACK after dropping
5

Observe: the sodium floats, melts into a ball, darts across the surface, fizzes (H₂ evolution), and the water turns pink (NaOH + phenolphthalein).

5 Min. Do not lean over the trough
6

After the reaction is complete, test the pH of the solution with pH paper (should be >12).

3 Min. Solution is now corrosive NaOH
7

Discuss: Group 1 reactivity trend (Li < Na < K < Rb < Cs), the redox nature of the reaction, and why sodium floats (density 0.97 g/mL < 1.0 g/mL).

7 Min.

Erwartete Ergebnisse

The sodium piece fizzes vigorously on the water surface, darting around as hydrogen is released. It melts into a shiny ball. The phenolphthalein turns the water bright pink in a spreading pattern. With very small pieces, no flame occurs; slightly larger pieces may produce a yellow sodium flame.

Aufräumen

Neutralize the NaOH solution with dilute HCl before disposing down the drain. Ensure no unreacted sodium remains. Clean the trough thoroughly.

Details

Kategorie
Classroom Demonstrations
Schwierigkeit
Advanced (University)
Dauer
25 Min.
Geschätzte Kosten
$12,00
Schritte
7
Materialien
4

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Frequently Asked Questions

What is the objective of Reaktion von Natrium und Wasser?
Die Reaktivität von Alkalimetallen demonstrieren, indem Natrium mit Wasser zur Reaktion gebracht und die Wasserstoffentwicklung sowie die Hydroxidbildung beobachtet wird.
How difficult is Reaktion von Natrium und Wasser?
This experiment is rated as Advanced (University). It takes approximately 25 minutes to complete.
What safety precautions are needed for Reaktion von Natrium und Wasser?
Key safety precautions include: Sodium is highly reactive — NEVER handle with bare hands; Keep sodium away from water until ready for demonstration; Cut sodium on a dry tile; keep pieces small (pea-sized maximum).
What materials are needed for Reaktion von Natrium und Wasser?
The main materials required are: Sodium metal, Phenolphthalein indicator, Distilled water, Mineral oil.
What results should I expect from Reaktion von Natrium und Wasser?
The sodium piece fizzes vigorously on the water surface, darting around as hydrogen is released. It melts into a shiny ball. The phenolphthalein turns the water bright pink in a spreading pattern. With very small pieces, no flame occurs; slightly larger pieces may produce a yellow sodium flame.