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Zorluk: OrtaAlkali Metals: Sodium Extraction, Properties, and Compounds

What is the correct chronological sequence of steps involved in the industrial extraction of sodium metal using the Downs process, from raw material preparation to the final collection of the metallic product?

  1. 1Purification and thorough drying of rock salt to obtain pure anhydrous sodium chloride (NaClNaCl).
  2. 2Mixing anhydrous sodium chloride with calcium chloride (CaCl2CaCl_2) to depress the melting point of the salt.
  3. 3Fusion of the salt mixture and application of direct electric current within the Downs cell.
  4. 4Preferential discharge of sodium ions (Na+Na^+) at the iron cathode and chloride ions (Cl−Cl^-) at the graphite anode.
  5. 5Collection of liquid sodium as it floats up the cathode compartment into an inverted dome receiver.

Cevap

The correct sequence begins with purifying and drying rock salt to yield anhydrous NaClNaCl, followed by mixing in CaCl2CaCl_2 to lower the fusion temperature. The mixture is then melted and electrolyzed in the Downs cell, leading to the reduction of Na+Na^+ at the cathode, and finally collecting liquid sodium as it floats to the top of the molten electrolyte.
The industrial extraction of sodium metal via the Downs process requires a strict sequence: raw rock salt is first purified and dried to remove water, then mixed with CaCl2CaCl_2 flux to lower the melting point to about 600∘C600^\circ\text{C}. This solid mixture is melted in the cell, where direct current electrolyzes the melt, reducing Na+Na^+ at the iron cathode. Finally, the buoyant molten sodium rises to the top of the cathode chamber and is harvested in a nitrogen environment.

Adım Adım Çözüm

1
Identify raw material pretreatment
Anhydrous NaClNaCl is prepared by removing moisture and impurities.
Water must be completely eliminated to prevent hydrogen discharge and hazardous reactions with sodium metal.
2
Identify flux addition step
CaCl2CaCl_2 is added to form a binary eutectic mixture.
Lowering the melting point from 801∘C801^\circ\text{C} to approximately 600∘C600^\circ\text{C} reduces operating costs and sodium vaporization.
3
Identify electrolytic cell setup and power application
The mixture is fused and direct current is passed through molten NaClNaCl/CaCl2CaCl_2.
Electrolysis requires mobile ions in a molten state to conduct electricity.
4
Identify electrode reactions
Reduction: Na++e−→Na(l)Na^+ + e^- \rightarrow Na(l) at cathode; Oxidation: 2Cl−→Cl2(g)+2e−2Cl^- \rightarrow Cl_2(g) + 2e^- at anode.
Na+Na^+ ions migrate to the iron cathode and accept electrons, while Cl−Cl^- ions migrate to the graphite anode.
5
Identify product separation and harvest
Molten sodium metal floats above the dense molten electrolyte into a collection riser.
The lower density of molten sodium (0.97 g/cm30.97\text{ g/cm}^3) relative to molten electrolyte (2.1 g/cm32.1\text{ g/cm}^3) allows passive buoyancy separation.

Anahtar Kavram

Downs Process for Sodium Extraction
Tahmini Süre:1m 30s
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Alkali Metals: Sodium Extraction, Properties, and Compounds

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