Question

Starting with sodium chloride how would you proceed to prepare (i) sodium metal (ii) sodium hydroxide (iii) sodium peroxide (iv) sodium carbonate ?

Short answer

Convert sodium chloride to sodium metal by electrolysis, then use sodium metal to prepare other compounds.

Step-by-step solution

Preparation of Sodium Metal

To prepare sodium metal from sodium chloride, perform electrolysis of molten sodium chloride. Set up an electrolytic cell with an iron cathode and graphite anode. During electrolysis, sodium ions move towards the cathode and reduce to form sodium metal.\[ \text{Na}^+ + e^- \rightarrow \text{Na} \]

Preparation of Sodium Hydroxide

React sodium metal with water to form sodium hydroxide and hydrogen gas. Be cautious as the reaction is exothermic.\[ 2 \text{Na} + 2 \text{H}_2\text{O} \rightarrow 2 \text{NaOH} + \text{H}_2 \]

Preparation of Sodium Peroxide

React sodium metal with oxygen gas in a controlled environment to form sodium peroxide.\[ 2 \text{Na} + \text{O}_2 \rightarrow \text{Na}_2\text{O}_2 \]

Preparation of Sodium Carbonate

React sodium hydroxide with carbon dioxide to form sodium carbonate and water.\[ 2 \text{NaOH} + \text{CO}_2 \rightarrow \text{Na}_2\text{CO}_3 + \text{H}_2\text{O} \]

Key concepts

Sodium Chloride

Sodium chloride, commonly known as table salt, is an essential compound in chemistry. With the chemical formula \( \text{NaCl} \), it consists of sodium (Na) and chlorine (Cl) ions. Sodium chloride is vital in many areas, including food, industry, and laboratory settings. In water, it dissociates into sodium ions \( \text{Na}^+ \) and chloride ions \( \text{Cl}^- \). However, to obtain sodium metal from sodium chloride, you cannot rely on simple dissolution. Instead, a more sophisticated technique known as electrolysis is employed. This process involves using the molten (liquid) state of sodium chloride rather than its aqueous form, allowing for the separation of sodium ions from chloride ions under electrical influence.

Electrolysis Process

The electrolysis process is a significant method for obtaining sodium metal from sodium chloride. This method involves using an electrolytic cell, which consists of an iron cathode and a graphite anode immersed in molten sodium chloride. When an electric current passes through, it prompts the movement of charged ions:

• Positive sodium ions \( \text{Na}^+ \) are drawn towards the negatively charged iron cathode, where they gain an electron (reduction) to form sodium metal \( \text{Na} \).
• Simultaneously, at the graphite anode, negative chloride ions \( \text{Cl}^- \) lose electrons (oxidation) and form chlorine gas \( \text{Cl}_2 \).

This conversion is represented by the half-equation \( \text{Na}^+ + e^- \rightarrow \text{Na} \). The result is the isolation of sodium metal, and due to its highly reactive nature, it must be carefully handled once produced.

Sodium Reactions

Sodium's reactive properties lead to various significant chemical reactions. Its vigorous reaction with water forms sodium hydroxide and hydrogen gas:

• The equation for this reaction is \( 2 \text{Na} + 2 \text{H}_2\text{O} \rightarrow 2 \text{NaOH} + \text{H}_2 \), releasing hydrogen in its gaseous state.
• Due to its exothermic nature, where heat is released, extreme caution is advised during this process.

Additionally, reacting sodium with oxygen produces sodium peroxide \( \text{Na}_2\text{O}_2 \), which serves in applications like bleach or disinfectants. These reactions highlight sodium's reactivity and utility across different chemical contexts.

Chemical Synthesis Steps

After obtaining sodium metal, it can serve as a precursor for synthesizing various sodium compounds. Consider these steps for further chemical synthesis:

• Sodium Hydroxide: Reconcile sodium metal with water under controlled conditions to produce sodium hydroxide \( \text{NaOH} \), commonly used in cleaning agents and industrial processes.
• Sodium Peroxide: Create sodium peroxide \( \text{Na}_2\text{O}_2 \) by direct reaction of sodium metal and oxygen. This compound is useful for bleaching textiles and other oxidizing applications.
• Sodium Carbonate: Achieve sodium carbonate \( \text{Na}_2\text{CO}_3 \) by reacting sodium hydroxide with carbon dioxide. Known as soda ash, it's found in glass production and as a water softener.

Each step reflects a strategic transformation, illustrating the fascinating versatility of sodium in industrial and chemical synthesis projects.