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Caustic Soda, Washing Soda and Baking Soda – Preparation, Chemical Formula, Properties

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  • Last Updated : 05 Oct, 2021

Salt is a mineral comprised largely of sodium chloride (NaCl), a chemical component that belongs to the wider class of salts; rock salt or halite is salt in the form of a natural crystalline mineral. Seawater contains a large amount of salt. The open ocean has a salinity of 3.5 % and around 35 grammes (1.2 oz) of solids per litre of seawater. Salt is made by evaporating seawater (sea salt) and mineral-rich spring water in shallow pools, as well as from salt mines. 

Caustic soda and chlorine are its main industrial products; salt is used in a variety of industrial processes, including the production of polyvinyl chloride, polymers, paper pulp, and a variety of other items. Only around 6% of the world’s yearly salt production of around 200 million tonnes is used for human use. 

Other applications include water treatment, roadway de-icing, and agricultural use. Sea salt and table salt, for example, are edible salts that normally contain an anti-caking agent and can be iodized to prevent iodine shortage. Sodium serves as an electrolyte and an osmotic solute, making it an important nutrient for human health. Excessive salt consumption in children and adults may raise the risk of cardiovascular illnesses such as hypertension. As a result, several international health organisations and specialists in industrialised countries advise cutting back on salty meals. Adults should take fewer than 2,000 milligrammes of sodium per day, or 5 grammes of salt, according to the World Health Organization.

Caustic Soda (Sodium Hydroxide) 

Caustic soda, often known as Lye, is an alkali salt. Sodium hydroxide is known by this term. The corrosive impact of this salt on animal and plant tissues has earned it this name. It can be used in a variety of ways. NaOH is the chemical formula for sodium hydroxide.

Preparation of  Caustic Soda:

Sodium hydroxide can be made in a variety of ways, including:

  1. Castner-Kellner process
  2. Nelson Diaphragm cell
  3. Loewig’s process

Castner-Kellner process:

Principle: Electrolysis of brine solution is used in the Castner-Kellner process to obtain sodium hydroxide.

Castner-Kellner cell: It’s a rectangular steel tank made of steel. The tank is lined with ebonite. The anode is titanium, while the cathode is a layer of mercury at the bottom of the tank.

The reaction that causes ionisation of brine solution is as follows:

2NaCl → 2Na+ + 2Cl

Ionization occurs when the brine solution comes into touch with an electric current. As a result, both positive and negative ions are drawn to the electrodes. A sodium amalgam is formed when sodium ions are deposited at the mercury cathode. Chlorine ions travel from the top of the cell to the anode.

  • Reaction at the anode:

2Cl→ Cl2 + 2e

  • Reaction at the cathode:

2Na+ + 2e→ 2Na

Formation of NaOH: The amalgam is then moved to a chamber known as the denuder. It is processed with water in the denuder to produce a sodium hydroxide solution. Solid sodium hydroxide is generated as the solution evaporates. Obtaining pure caustic soda is a very effective method.

Properties of Caustic Soda:

  • It’s a white solid with a melting point of 591 degrees Celsius.
  • It’s a long-lasting substance.
  • NaOH is bitter and soapy to the touch.
  • It has high water solubility and moderate alcohol solubility.
  • Sodium hydroxide is an alkaline substance.

Uses of Caustic Soda

  1. It’s a cleaning agent, and it’s also used to make washing soda.
  2. In some laboratories, sodium hydroxide is also utilised as a reagent.
  3. It’s a key ingredient in the production of soda-lime.
  4. It is used to cleanse bauxite in order to obtain aluminium.

Washing soda (Sodium Carbonate)

Washing soda is used in a variety of applications, ranging from home to industrial. It’s an alkaline substance with a high alkaline character that can eliminate stubborn stains from textiles while they’re being washed. The formula for washing soda is Na2CO3.10H2O. Sodium carbonate is the chemical term for washing soda. Soda ash is a hydrated salt of sodium carbonate in chemical terms.

Preparation of Sodium Carbonate:

The Solvay method is required for the synthesis of sodium carbonate, and the steps involved in sodium carbonate manufacturing are described below:

Step 1: Purification of Brine

Evaporation produces concentrated brine, while precipitation removes impurities such as calcium, magnesium, and other minerals. The concentrated brine solution is filtered before being mixed with ammonia in the ammonia tower, which is then cooled.

Step 2: Formation of sodium hydrogen carbonate

Carbon dioxide is transported via an ammoniated brine solution in a carbonating tower.

NH3 + CO2 + NaCl +H2O → NaHCO3 + NH4Cl

Step 3: Formation of sodium carbonate

The sodium bicarbonate (NaHCO3) that is generated is collected from the tower and heated to 300°C. As a result, sodium carbonate crystals form.

2NaHCO3 → Na2CO3 + CO2 + H2O

Step 4: Recovery of ammonia

By treating an NH4Cl solution with Ca(OH)2, ammonia can be recovered. The Solvay process uses this ammonia again, and CaCl2 is obtained as a by-product.

2NH4Cl + Ca(OH)2 → 2NH3 + CaCl2 + H2O

Properties of sodium carbonate:

  • It’s a crystalline solid that’s white in colour.
  • It comes in monohydrated (Na2CO3.10H2O), anhydrous (Na2CO3), heptahydrous (Na2CO3.7H2O), and decahydrate (Na2CO3.7H2O) forms (Na2CO3.10H2O).
  • In nature, sodium carbonate is a basic substance.
  • It has a melting point of 851 degrees Celsius.
  • It loses its water in the presence of heat and forms an anhydrous salt (soda ash).

Na2CO3.10H2O → Na2CO3.H2O → Na2CO3 (at 373 K)

Uses of Washing Soda:

  1. In industry and the home, it is used as a cleaning agent.
  2. It’s used in the paper, textile, soap, and detergent sectors, among others.
  3. It is utilised in the water softening process.
  4. It’s a material used in the production of glass.
  5. In laundries, it is one of the most significant agents.

Baking Soda (sodium bicarbonate)

Sodium bicarbonate is also known as baking soda. Baking soda’s chemical formula is NaHCO3.

Sodium Bicarbonate is another name for baking soda. Natron, a natural deposit mostly composed of Na2CO3, was first quarried by the Medieval Egyptians. It was used as soap. Nicolas Leblanc, a French chemist, created NaHCO3 for the first time in 1971. In 1846, John Dwight and Austin Church established a baking soda manufacturing plant employing sodium carbonate and carbon dioxide.

Various chemistry applications can be found in every room of the house, including the bathroom, kitchen, and so on. Sodium bicarbonate is one such substance, which is widely utilised due to its versatility, utility, and low cost.

Preparation of Baking Soda:

In the industrial world, the Solvay process is used to make sodium bicarbonate and sodium carbonate. Carbon dioxide, water, ammonia, and concentrated brine solution are employed as raw materials in this process. This method is preferred because it is less expensive and requires less raw resources to create the required chemicals. Baking soda and sodium carbonate are made through a chemical reaction that goes like this:

CO2 + H2O + NH3 + NaCl → NaHCO3 + NH4Cl

2 NaHCO3 → Na2CO3 + CO2 + H2O

The carbon dioxide that is created is recycled to make NaHCO3.

Properties of Sodium Bicarbonate:

  • It is non-combustible.
  • Powder dust isn’t as explosive as other types of dust.
  • It has a 50-degree melting point.
  • NaHCO3 is a crystalline white substance with no odour.
  • It is fundamental in nature.

Uses of Baking Soda:

  1. Reduces stomach acidity and acts as an antacid to relieve stomach discomfort and indigestion.
  2. As a water softener, it is used in the washing process.
  3. It is utilised in fire extinguishers because it produces soapy foam.
  4. Acts as a pesticide by removing dirt from materials without affecting their properties.
  5. Carbon dioxide is produced (due to the decomposition of NaHCO3), which aids in the rising of dough in the baking industry.
  6. It’s found in ear drops, cosmetics, and other personal care items.
  7. It’s utilised to counteract the effects of acid by acting as a neutralizer.

Sample Questions

Question 1: What part of the industrial cleaning process does caustic soda play?

Answer:

Caustic soda is used to clean process equipment and storage tanks because it dissolves grease, protein-based deposits, fats, and oil when mixed with water and heated.

Question 2: What are the health risks associated with caustic soda?

Answer:

NaOH is extremely corrosive and unpleasant. It produces severe burns to the skin.

Question 3: Write any two of Caustic Soda’s principal applications.

Answer:

The following are some of the applications for caustic soda:

  • In the production of petroleum-based goods.
  • It’s utilised in the pulp and paper industries.

Question 4: What are the four stages that go into making sodium carbonate?

Answer:

The following are the four steps involved in making sodium carbonate:

  • Brine Purification
  • Sodium hydrogen carbonate is formed.
  • Sodium carbonate is formed.
  • Ammonia is recovered.

Question 5: Write any two uses of Washing soda.

Answer:

Uses of Washing soda are:

  • In industry and the home, it is used as a cleaning agent.
  • It’s used in the paper, textile, soap, and detergent sectors, among others.

Question 6: What are the properties of sodium bicarbonate?

Answer:

Following are the properties of sodium bicarbonate:

  • It is non-combustible.
  • Powder dust isn’t as explosive as other types of dust.
  • It has a 50-degree melting point.
  • NaHCO3 is a crystalline white substance with no odour.
  • It is fundamental in nature.

Question 7: What are the uses of baking soda?

Answer:

The following are the uses of baking soda:

  1. Reduces stomach acidity and acts as an antacid to relieve stomach discomfort and indigestion.
  2. As a water softener, it is used in the washing process.
  3. It is utilised in fire extinguishers because it produces soapy foam.
  4. Acts as a pesticide by removing dirt from materials without affecting their properties.
  5. Carbon dioxide is produced (due to the decomposition of NaHCO3), which aids in the rising of dough in the baking industry.
  6. It’s found in ear drops, cosmetics, and other personal care items.
  7. It’s utilised to counteract the effects of acid by acting as a neutralizer.

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