Plaster Of Paris, Baking Soda and Washing Soda

What Plaster Of Paris, Baking Soda and Washing Soda?

Sodium bicarbonate commonly known as baking soda is a chemical compound with the formula NaHCO₃. It is a salt composed of a sodium cation and a bicarbonate anion. Baking soda can be obtained from Sodium carbonate, recrystallization of sodium carbonate gives washing soda. It is also called a basic salt.

Plaster of Paris is obtained by heating gypsum. The chemical formula of plaster of Paris is CaSO₄.1/2H₂O. Plaster of Paris is a white powder and on mixing with water it changes to gypsum resulting in a hard solid mass. It is mainly used by doctors as a plaster for setting the fractured bones in the right position.

Table of Contents

• Plaster of Paris
• Recommended Videos
• Washing Soda
• Baking Soda
• Frequently Asked Questions – FAQs

1. Plaster of Paris

Plaster of Paris is a chemical compound consisting of fine white powder, which hardens when exposed to moisture and allowed to dry. Its chemical formula of Plaster of Paris is CaSO₄.1/2H₂O and is better known as calcium sulphate hemihydrate.

Preparation of Plaster of Paris

Plaster of Paris is synthesized from gypsum (CaSO₄.2H₂O). When gypsum is heated at 373 K, it loses its water molecules to become calcium sulphate (plaster of Paris).

CaSO₄.2H₂O → CaSO₄.1/2H₂O + 3/2H₂O

Uses of Plaster of Paris

• Plaster of Paris is used by doctors for supporting fractured bones in the right position.
• It is used for making toys and decorative materials.
• It is also used for increasing the smoothness of surfaces.

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2. Washing Soda

Washing soda is a whitish, odourless powder. Its chemical formula is Na₂CO₃.10H₂O and is better known as sodium carbonate decahydrate. It is hygroscopic in nature that is, it absorbs moisture from the air. It is highly soluble in water and forms a strongly alkaline water solution.

Preparation of Washing Soda

Washing soda is synthesized through Solvay’s process. Solvay’s process involves the reaction of sodium chloride, ammonia and carbon dioxide in water. Carbon dioxide involved is produced through calcium carbonate and the calcium oxide left is used in recovering ammonia from ammonium chloride.

At first, sodium bicarbonate is obtained which is then converted to sodium carbonate on heating. Finally, washing soda is produced by recrystallization of sodium carbonate.

• NaCl + NH₃ + CO₂ + H₂O → NaHCO₃ + NH₄Cl
• 2 NaHCO₃ → Na₂CO₃ + H₂O + CO₂
• Na₂CO₃ + 10H₂O → Na₂CO₃.10H₂O

Uses of Washing Soda

• Washing soda is used for removing burnt-on grease from kitchen utensils.
• It is prominently used in soap, glass and paper industries.
• It also helps in the removal of permanent hardness of the water.
• It acts as a raw material in the manufacturing of various sodium compounds, for example, borax.

3. Baking Soda

Baking soda is a white crystalline compound with a slightly salty taste. Its chemical formula is NaHCO₃ and is generally known as sodium bicarbonate.

Baking Soda – a white crystalline compound

Preparation of Baking Soda

Baking soda is synthesized through Solvay’s process. Solvay’s process involves the reaction of sodium chloride, ammonia and carbon dioxide in water. The carbon dioxide involved is produced through calcium carbonate and the calcium oxide left is used in recovering ammonia from ammonium chloride. Finally, sodium bicarbonate is produced as one of the end products.

NaCl + H₂O + CO₂ + NH₃  → NH₄Cl + NaHCO₃

Uses of Baking Soda

• It is used in making soft and fluffy bread and cakes due to the production of carbon dioxide when it is heated or mixed in water.

NaHCO₃ + H⁺   → CO₂ + H₂O + sodium salt of acid

• It is used for making soda-acid fire extinguisher.
• It is used as an ingredient in the manufacturing of antacids.

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