Sodium

Table of Content

Minerals of Sodium
Extraction of Sodium
Properties of Sodium
Uses of Sodium
Sodium Hydroxide/ Caustic Soda
- Electreolystic Process for perparation of NaOH
- Properties
Related Resources

Sodium is the 7^th most abundant element by weight found in earth’s crust.
Atomic Number: 11
Atomic Weight: 23
Electronic Configuration: 1s² 2s² sp⁶ 3s¹
Valency : 1

Minerals of Sodium

Chile salt petre	NaNO₃
Glauber’s salt	Na₂SO₄.10H₂O
Borax or sodium borate	Na₂B₄O₇.10H₂O
Rock salt	NaCl
Albite or soda feldspar	Na₂O.Al₂O₃.6SiO₂ or NaAlSi₃O₈

Extraction of Sodium

Sodium is extracted by Down’s process through electrolysis of fused sodium chloride.

In this method, sodium is obtained by the electrolysis of mixture of sodium chloride (40%) and calcium chloride (60%) in fused state. The function of calcium chloride is to lower the operating temperature from 1080 K (m.pt. of NaCl) to about 850 K. The main reason for lowering the temperature are:

The melting point of sodium chloride is very high it is very difficult to maintain it in the molten state during electrolysis.
Sodium is considerably volatile at the temperature needed for the electrolysis and therefore, a part of the metal produced is vapourised.
Molten sodium gets dispersed in molten chloride to form a metallic fog (colloidal solution) at high temperature.
Both sodium and chlorine, the two products of the electrolysis, have a corrosive action on the material of the vessel employed for the electrolysis at such a high temperature.

The cell consists of a steel tank lined with fire bricks. A circular graphite anode is placed in the centre of the cell which is surrounded by a cylindrical iron cathode. The anode and cathode are separated by a steel gauge cylinder through which molten sodium chloride can pass but molten sodium cannot. The purpose of using steel gauge is to keep sodium separate from chlorine which would otherwise react with chlorine. The anode is covered by a dome – shaped steel hood which provides the out – let for the escape of chlorine gas. The molten metal liberated at the cathode moves up and flow into the receiver containing kerosene oil. The following reactions take place:

NaCl → Na⁺+Cl^-(Ionization)

At Cathode: Na+ + e^- → Na

At ande: Cl^- + Cl^- → Cl₂

Properties of Sodium

Sodium is a soft white metal with silver – like lustre, and can also be obtained in tetragonal crystalline form. It dissolves in liquid ammonia, giving intense blue solution. The colloidal sodium in ether medium can be obtained by Svedbergls method by suspending the metal in ether and passing an oscillatory discharge from Letden jar arrangement. The colour of colloid is violet. The metal burnes in air to form Na₂O and Na₂O₂. When heated with mercury, it forms an amulgam of varying compositions, NaHg, NaHg₄ etc. In the organic qualititative work, the fusion with sodium metal is a common process. It is soluble in alcohol, forming C₂H₅ONa and is very much used as such. When sodium is heated with ammonia gas, sodamide is formed

2NH₃ + 2Na $\overset{300-400}{\rightarrow}$ 2NaNH₂ +H₂

It combines with a number of non-metals on heating

2Na + Cl₂ → 2NaCl

2Na + S → 2Na₂S

2Na + H₂ → 2NaH

With water, a violent action takes place and hydrogen gas is evolved.

2Na + 2H₂O→ 2NaOH + H₂

It displaces hydrogen from acids

2HCl + 2Na → 2NaCl + H₂

It acts as a reducing agents because of its ease with which it can lose its valence electron.

Al₂O₃ + 6Na → 2Al + 3Na₂O

SiO₂ + 4Na → Si + 2Na₂O

CO₂ + 4Na → 2Na₂CO₃ + C

Uses of Sodium

Following are some of the many uses of sodium metal

In the manufacturing of sodium peroxide, sodium cyanide and sodium methoxide
As a reducing agent in the extraction of boron and silicon in the form of sodium amalgam.
As a reagent in organic analysis.
Because of its high thermal conductivity, it is employed for filling valves of aircraft engines.
In the production of rich yellow light by sealing it in electric bulb containing argon or mercury vapour.
In organic reactions such as condensation, polymerization, isomerization and preparation of metal alkyls and aryls.

Sodium Hydroxide/ Caustic Soda (NaOH)

Caustic soda is an article of great commercial importance and, therefore, is prepared on a large scale.

Electreolystic Process for perparation of NaOH

This involves the electrolysis of a solution of sodium chloride. The solution contains sodium, chloride, hydrogen and hydroxide ions. In passing the current sodium and hydrogen ions move toward the cathode but hydrogen ions are able to accept the electrons more easily than sodium ions, with the result that hydrogen gas is liberated with the decomposition of more water molecules while sodium ions remain in the solution. At anode chloride ions give up electrons in preference to hydroxide ions and thus chlorine gas is liberated there.

At Anode	At cathode	Overall reaction
2H₂O + 2e → H₂ + OH^-	2Cl^- → Cl₂ + 2e	2Na⁺+Cl-+H₂O → 2Na⁺+OH^- +H₂ +Cl₂

The solution on electrolysis , therefore , becomes richer in sodium hydroxide

When calcium hydroxide is added to sodium carbonate solution, calcium carbonate is precipitated, leaving sodium hydroxide in solution

Na₂CO₃ + Ca(OH)₂ → CaCO₃ ¯ + 2NaOH

Properties

NaOH is stable towards heat but is reduced to metal when heated with carbon

2NaOH + 2C → 2Na +2CO + H₂

FeCl₃ + 3NaOH → Fe(OH)₃ + 3NaCl

NH₄Cl + NaOH → NaCl + NH₃ (pungent smell) + H₂O

HgCl₂ + 2NaOH → HgO (yellow powder) + 2NaCl + H₂O

Zn(OH)₂ ¯ + 2NaOH → Na₂ZnO₂ + 2H₂O

Al₂O₃ ¯ + 2NaOH → 2NaAlO₂ + H₂O

SiO₂ + 2NaOH→ Na₂SiO₃ + H₂O

3P + 3 NaOH +3H₂O→ PH₃ + 3NaH₂PO₂

2Al + 2 NaOH + 2H₂O → 3H₂ + 2NaAlO₂

Question 1: Valency of Sodium metal is

a. 1

b. 2

c. 3

d. 4

Question 2: Which of the following compounds is not an ore of sodium metal?

a. Glauber’s salt

b. Rock salt

c. Albite

d. Lignite

Question 3: Which gas is produced at anode during electrolysis of sodium chloride?

a. Hydrogen

b. Chlorine

c. Oxygen

d. Hydrogen chloride

Question 4: Zn(OH)₂^¯ + 2NaOH → Na₂ZnO₂ + ?

a. H₂

b. H₂O

c. Na₂O

d. NaOH

Q.1	Q.2	Q.3	Q.4
a	d	a	b

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