Definition Preparation Chemical Reactions Properties and Uses of Baking Soda Washing Soda and Plaster Of Paris
Baking Soda, Washing Soda, Plaster of Paris is essential in chemistry and helps students understand various practical and theoretical applications related to this topic.
What is Baking Soda, Washing Soda, Plaster of Paris in Chemistry?
The term Baking Soda, Washing Soda, Plaster of Paris refers to three important inorganic compounds widely used in daily life and industry. Baking soda is sodium bicarbonate, washing soda is sodium carbonate decahydrate, and plaster of Paris is calcium sulfate hemihydrate. This concept appears in chapters related to salts, industrial chemistry, and everyday chemistry, making it a foundational part of your chemistry syllabus.
Molecular Formula and Composition
The molecular formulas of these three compounds are given below. Each consists of different ions and hydration states, and all are classified as common salts or chemical compounds.
| Compound | Molecular Formula | IUPAC Name |
|---|---|---|
| Baking Soda | NaHCO3 | Sodium hydrogen carbonate |
| Washing Soda | Na2CO3·10H2O | Sodium carbonate decahydrate |
| Plaster of Paris | CaSO4·½H2O | Calcium sulfate hemihydrate |
Preparation and Synthesis Methods
Baking soda is prepared using the Solvay process, which reacts sodium chloride, ammonia, carbon dioxide, and water to form sodium bicarbonate and ammonium chloride.
Washing soda is produced by heating baking soda (sodium bicarbonate) to obtain sodium carbonate. This sodium carbonate is dissolved in water and recrystallized to give washing soda crystals.
Plaster of Paris is manufactured by heating gypsum (CaSO4·2H2O) at about 150°C, removing part of the water of crystallization and forming calcium sulfate hemihydrate.
Physical Properties of Baking Soda, Washing Soda, Plaster of Paris
- Baking soda: White crystalline powder, slightly salty, soluble in water, alkaline in nature.
- Washing soda: White, granular solid, crystalline, highly soluble, strongly alkaline, slippery.
- Plaster of Paris: Soft, fine white powder, sets quickly with water, forms a hard mass, slightly soluble in water.
Chemical Properties and Reactions
Baking soda decomposes on heating, releasing CO2 and leaving sodium carbonate behind:
NaHCO3 (heat) → Na2CO3 + CO2 + H2O
Washing soda is formed by crystallizing sodium carbonate. It reacts with acids to release CO2.
Plaster of Paris reacts with water to form gypsum:
CaSO4·½H2O + 1½H2O → CaSO4·2H2O
Frequent Related Errors
- Confusing the formulas of baking soda and washing soda.
- Mixing up preparation reactions of plaster of Paris with gypsum.
- Writing wrong water of crystallization in chemical formulas.
- Using the compounds interchangeably in applications.
Uses of Baking Soda, Washing Soda, Plaster of Paris in Real Life
Baking soda is widely used in cooking, antacid medicine, and fire extinguishers. Washing soda is used in cleaning agents, water softening, and textile/dye industries. Plaster of Paris is important in making casts for broken bones, sculptures, decorative articles, and construction work.
Relevance in Competitive Exams
Students preparing for NEET, JEE, and Olympiads should be familiar with Baking Soda, Washing Soda, Plaster of Paris, as it often features in reaction-based and concept-testing questions. Chemical formulas, preparation processes, and differences are frequently asked in CBSE board exams.
Relation with Other Chemistry Concepts
Baking soda, washing soda, and plaster of Paris are closely related to topics such as salts and crystallization and industrial salts, helping students build a conceptual bridge between acids, bases, and real-world applications of salts.
Step-by-Step Reaction Example
1. Start with heating baking soda (NaHCO3):2. Obtain sodium carbonate (washing soda) by dissolving and crystallizing:
3. For plaster of Paris, heat gypsum:
Lab or Experimental Tips
Remember that heating causes baking soda to release CO2 and produce washing soda as a residue. Vedantu educators often use this tip in live sessions to simplify how thermal decomposition reactions can be tested in the lab. When handling plaster of Paris, always add powder to water (and not the reverse) for smoother mixing and safety.
Try This Yourself
- Write the IUPAC name and formula of baking soda, washing soda, and plaster of Paris.
- Show the equation for heating sodium bicarbonate to convert it into washing soda.
- List two household and two industrial uses of each compound.
Final Wrap-Up
We explored Baking Soda, Washing Soda, Plaster of Paris—its structure, properties, reactions, and real-life importance. For more in-depth explanations and exam-prep tips, explore live classes and notes on Vedantu. Accurate knowledge of these compounds lays a strong foundation for advanced chemistry topics and daily science applications.
FAQs on Baking Soda Washing Soda and Plaster Of Paris in Chemistry
1. What is baking soda in chemistry?
Baking soda is sodium hydrogen carbonate (NaHCO3), a mild alkaline salt commonly used in cooking and chemistry.
- It is also called sodium bicarbonate.
- It is a white crystalline solid, soluble in water.
- On heating, it decomposes as: 2NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g).
- It is used as a leavening agent because it releases carbon dioxide gas.
2. What is washing soda and what is its chemical formula?
Washing soda is sodium carbonate decahydrate (Na2CO3·10H2O), a hydrated salt of sodium carbonate.
- It is obtained by crystallizing sodium carbonate with water.
- It is strongly alkaline in nature.
- On heating, it loses water of crystallization to form Na2CO3.
- It is used in cleaning, softening hard water, and glass manufacture.
3. What is Plaster of Paris and what is its formula?
Plaster of Paris is calcium sulphate hemihydrate (CaSO4·½H2O), formed by partial dehydration of gypsum.
- It is prepared by heating gypsum: CaSO4·2H2O(s) → CaSO4·½H2O(s) + 1½H2O(g).
- It is a white powder that sets into a hard mass when mixed with water.
- It is widely used for making moulds, statues, and casts.
4. What is the difference between baking soda and washing soda?
The main difference between baking soda and washing soda is that baking soda is NaHCO3 while washing soda is Na2CO3·10H2O.
- Baking soda: Mild base, used in baking and as an antacid.
- Washing soda: Stronger base, used in cleaning and water softening.
- Baking soda releases CO2 on heating; washing soda mainly provides carbonate ions in solution.
5. How is washing soda prepared from baking soda?
Washing soda is prepared from baking soda by heating sodium hydrogen carbonate to form sodium carbonate, followed by crystallization.
- Step 1 (Thermal decomposition): 2NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g).
- Step 2 (Crystallization): Na2CO3(aq) + 10H2O(l) → Na2CO3·10H2O(s).
- The final product is washing soda crystals.
6. How does baking soda react with acids?
Baking soda reacts with acids to produce a salt, water, and carbon dioxide gas (CO2).
- Example with hydrochloric acid: NaHCO3(aq) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g).
- The reaction causes effervescence due to CO2 bubbles.
- This reaction is used in baking and fire extinguishers.
7. Why is Plaster of Paris stored in moisture-proof containers?
Plaster of Paris is stored in moisture-proof containers because it reacts with water to form hard gypsum.
- Reaction with water: CaSO4·½H2O(s) + 1½H2O(l) → CaSO4·2H2O(s).
- This process is called setting of Plaster of Paris.
- Exposure to moisture reduces its effectiveness by converting it back to gypsum.
8. What are the uses of washing soda in everyday life?
Washing soda is mainly used as a cleaning agent and water softener due to its alkaline nature.
- Removes permanent hardness of water by precipitating Ca2+ and Mg2+ as carbonates.
- Used in manufacturing glass, soap, and paper.
- Acts as a cleansing agent for domestic purposes.
9. What happens when Plaster of Paris is mixed with water?
When Plaster of Paris is mixed with water, it forms a paste that hardens into gypsum with the release of heat.
- Chemical reaction: CaSO4·½H2O(s) + 1½H2O(l) → CaSO4·2H2O(s).
- The reaction is exothermic.
- This property is used to make casts, moulds, and decorative items.
10. What is the chemical difference between gypsum and Plaster of Paris?
Gypsum is CaSO4·2H2O while Plaster of Paris is CaSO4·½H2O, differing in their water of crystallization.
- Gypsum contains two molecules of water per formula unit.
- Plaster of Paris contains half a molecule of water per formula unit.
- Heating gypsum at about 100–120°C forms Plaster of Paris.
