Sodium Carbonate and Sodium Bicarbonate: Differences and Formula

Sodium Carbonate and Sodium bicarbonate

Edited By Shivani Poonia | Updated on Jul 02, 2025 05:58 PM IST

Sodium bicarbonate, also referred to as baking soda, and sodium carbonate, also known as washing soda, are two different but equally useful substances.

Sodium carbonate (Na₂CO₃) is a white, crystalline solid, mostly produced by the Solvay Process. It is also present in hydrated forms such as decahydrate (Na₂CO₃·10H₂O). It becomes anhydrous soda ash at higher temperatures and is very soluble in water. This material is extensively utilized as an analytical reagent in laboratories and also in the laundering, glass-making, and water-softening industries. It is used in the manufacture of glass, soap, borax, and caustic soda also in paper, paints, and textile industries.

This Story also Contains

Sodium Carbonate
Sodium Bicarbonate
Some Solved Examples
Conclusion

Sodium Carbonate and Sodium bicarbonate

On the other hand, Sodium bicarbonate(NaHCO₃)is the result of the reaction between carbon dioxide and a saturated solution of sodium carbonate. Its basic properties in an aqueous solution are revealed when it appears as a white, crystalline solid with partial solubility in water. When heated, it breaks down to release carbon dioxide and becomes sodium carbonate. Sodium bicarbonate has several useful applications, such as reducing stomach acidity and being a main component of baking powder, fire extinguishers, and fizzy beverages. It is used in medicines as a mild antiseptic for skin infections. These materials demonstrate the many applications of sodium compounds in industry, medicine, and domestic products, highlighting their essential roles in modern chemistry and daily life.

Also read -

Sodium Carbonate

It is also known as washing soda.

Preparation

Sodium carbonate is generally prepared by the Solvay Process. In this process, the advantage is taken of the low solubility of sodium hydrogen carbonate whereby it gets precipitated in the reaction of sodium chloride with ammonium hydrogen carbonate. The latter is prepared by passing CO₂ to a concentrated solution of sodium chloride saturated with ammonia, where ammonium carbonate followed by ammonium hydrogen carbonate is formed. The equations for the complete process may be written as:

$\begin{aligned} & 2 \mathrm{NH}_3+\mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2 \rightarrow\left(\mathrm{NH}_4\right)_2 \mathrm{CO}_3 \\ & \left(\mathrm{NH}_4\right)_2 \mathrm{CO}_3+\mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2 \rightarrow 2 \mathrm{NH}_4 \mathrm{HCO}_3 \\ & \mathrm{NH}_4 \mathrm{HCO}_3+\mathrm{NaCl} \rightarrow \mathrm{NH}_4 \mathrm{Cl}+\mathrm{NaHCO}_3\end{aligned}$

Sodium hydrogen carbonate crystal separates. These are heated to give sodium carbonate.

$2 \mathrm{NaHCO}_3 \rightarrow \mathrm{Na}_2 \mathrm{CO}_3+\mathrm{CO}_2+\mathrm{H}_2 \mathrm{O}$

Properties

Sodium carbonate is a white crystalline solid which exists as a decahydrate,Na₂CO₃·10H₂O. This is also called washing soda.
It is readily soluble in water.
On heating, the decahydrate loses its water of crystallization to form monohydrate.
Above 373K, the monohydrate becomes completely anhydrous and changes to a white powder called soda ash.

Uses

It is used in water softening, laundering, and cleaning.
It is used in the manufacture of glass, soap, borax, and caustic soda.
It is used in paper, paints, and textile industries.
It is an important laboratory reagent both in qualitative and quantitative analysis.

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Sodium Bicarbonate

It is also known as baking soda.

Preparation

It is prepared by passing carbon dioxide through a saturated solution of sodium carbonate as follows:

$\mathrm{Na}_2 \mathrm{CO}_3+\mathrm{CO}_2+\mathrm{H}_2 \mathrm{O} \rightarrow 2 \mathrm{NaHCO}$
Sodium bicarbonate can be easily precipitated from here as it is less soluble in water.

Properties

It is a white crystalline solid partially soluble in water and its aqueous solution is basic. NaHCO₃ gives yellow colour with methyl red or methyl orange but no colour with HPH i.e., phenolphthalein.
On heating at 100^oC, it decomposes into Na₂CO₃ with the evolution of CO₂.
With zinc sulphate, it forms normal zinc carbonate.

$\mathrm{ZnSO}_4+2 \mathrm{NaHCO}_3 \longrightarrow \mathrm{ZnCO}_3+\mathrm{Na}_2 \mathrm{SO}_4+\mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2$
It reacts with dilute acids as follows:
$\mathrm{NaHCO} 3+\mathrm{HCl} \longrightarrow \mathrm{NaCl}+\mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2$

Uses

It is used to remove acidity in the stomach and in the making of baking powder (Sodium bicarbonate+potassium hydrogen tartrate).
It is used in fire extinguishers.
It is used in medicines as a mild antiseptic for skin infections.
It is used in making effervescent drinks.

Some Solved Examples

Q.1 A hydrated solid X on heating initially gives a monohydrated compound Y. The compound Y upon heating above 373K forms an anhydrous white powder Z.The compounds X and Z respectively are :

1) Washing soda and soda ash.

2) Baking soda and dead burnt plaster.

3) Washing soda and dead burnt plaster.

4) Baking soda and soda ash.

Solution:

As we learned

Na₂CO₃ crystallizes from water as decahydrate, called Washing soda, which effloresces on exposure to dry air forming monohydrate. On heating above 373K, the monohydrate becomes completely dehydrated to form anhydrous salt which is called soda ash. The reactions involved are depicted below$\mathrm{Na}_2 \mathrm{CO}_3 \cdot 10 \mathrm{H}_2 \mathrm{O}(\mathrm{s}) \xrightarrow{\Delta} \mathrm{Na}_2 \mathrm{CO}_3 \cdot \mathrm{H}_2 \mathrm{O}(\mathrm{s}) \underset{T>373 \mathrm{k}}{\Delta} \mathrm{Na}_2 \mathrm{CO}_3(\mathrm{~s})$

Hence, the answer is the option (1).

Q.2 By product in the formation of Na₂CO₃by Solvay process is :

1) NaCl

2) NH₃

3) NH₄OH

4) CaCl₂

Solution:

As we learned,

Manufacture of Na₂CO₃ by Solvay process -

Brine (NaCl), ammonia, and carbon dioxide are used as raw materials and calcium chloride is formed as a by-product

The reactions are given below:

$\begin{aligned} & \mathrm{NH}_3+\mathrm{CO}_2+\mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{NH}_4 \mathrm{HCO}_3 \\ & \mathrm{NH}_4 \mathrm{HCO}_3+\mathrm{NaCl}^{30^{-c}} \mathrm{NaHCO}_3 \downarrow+\mathrm{NH}_4 \mathrm{Cl} \\ & \mathrm{NaHCO}_3 \xrightarrow{250 \mathrm{C}} \mathrm{Na}_2 \mathrm{CO}_3+\mathrm{H}_2 \mathrm{O}+\mathrm{CO}_2 \\ & 2 \mathrm{NH}_4 \mathrm{Cl}+\mathrm{Ca}(\mathrm{OH})_2 \rightarrow \mathrm{CaCl}_2+2 \mathrm{H}_2 \mathrm{O}+2 \mathrm{NH}_3\end{aligned}$

Hence, the answer is the option (4).

Q 3. When decahydrate of washing soda is treated with dry air, the product formed in the given process is :

1) NaHCO₃.7H₂O

2) NaHCO₃.8H₂O

3) NaHCO₃.2H₂O

4) NaHCO₃.H₂O

Solution:

As we learned,

Na₂CO₃ crystallizes from water as a decahydrate. Upon exposure to dry air, it forms monohydrate

$\mathrm{Na}_2 \mathrm{CO}_3 \cdot 10 \mathrm{H}_2 \mathrm{O} \xrightarrow{\text { dry air }} \mathrm{Na}_2 \mathrm{CO}_3 \mathrm{H}_2 \mathrm{O}+9 \mathrm{H}_2 \mathrm{O}$

Hence, the answer is the option (4).

Also check-

NCERT Chemistry Notes:

Conclusion

Sodium carbonate (washing soda) and sodium bicarbonate (baking soda) are separate substances with a range of uses and characteristics

Sodium Carbonate (Na₂CO₃):-

Preparation: Generally produced by the Solvay Process, which combines ammonium hydrogen carbonate and sodium chloride in processes.
Properties: It is a crystalline white solid that dissolves in water; it is typically found as decahydrate or Na₂CO₃·10H₂O. When heated, it loses water molecules and becomes anhydrous soda ash.
Uses: Often used as a reagent in laboratory analyses, water softening, laundry, glass manufacturing, and soap production.

Sodium bicarbonate (NaHCO₃) :-

Preparation: Produced by treating carbon dioxide with a sodium carbonate saturated solution.
Characteristics: a white, crystalline solid that is somewhat soluble in water and forms a basic solution. At 100°C, it breaks down into sodium carbonate and releases carbon dioxide.
Uses: Frequently used as an ingredient in baking powder, fire extinguishers, and fizzy drinks to counteract stomach acidity. Additionally employed as a mild antiseptic in medical applications.

Frequently Asked Questions (FAQs)

1. What is washing soda, or sodium carbonate?

Sodium carbonate, a white crystalline substance with the chemical formula Na₂CO₃, is also referred to as washing soda or soda ash.

2. What are the uses of sodium carbonate?

Sodium carbonate finds application in the production of glass, as a water softener, in detergents and other cleaning goods, in papermaking, and in several chemical reactions.

3. What is baking soda, or sodium bicarbonate?

Sodium bicarbonate, commonly known as baking soda, The chemical formula for sodium bicarbonate, or baking soda, is NaHCO_3.

4. By which process Sodium Carbonate is prepared?

Solvay process

5. What is the difference between sodium carbonate and sodium bicarbonate?

Sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3) differ in their chemical composition and properties. Sodium carbonate has two sodium ions and one carbonate ion, while sodium bicarbonate has one sodium ion, one hydrogen ion, and one bicarbonate ion. This results in different pH levels when dissolved in water, with sodium carbonate being more alkaline than sodium bicarbonate.

6. How does sodium bicarbonate act as an antacid?

Sodium bicarbonate acts as an antacid by neutralizing excess stomach acid. When it reacts with hydrochloric acid in the stomach, it forms sodium chloride, water, and carbon dioxide. This reaction increases the pH of the stomach contents, providing relief from heartburn and indigestion.

7. What happens when you heat sodium bicarbonate?

When sodium bicarbonate is heated, it undergoes thermal decomposition. The reaction produces sodium carbonate, water vapor, and carbon dioxide gas. This process is represented by the equation: 2NaHCO3 → Na2CO3 + H2O + CO2. This decomposition is the basis for the use of baking soda in cooking, where it acts as a leavening agent.

8. How do sodium carbonate and sodium bicarbonate differ in their pH when dissolved in water?

When dissolved in water, sodium carbonate produces a more alkaline solution (pH around 11-12) compared to sodium bicarbonate (pH around 8-8.5). This is because sodium carbonate releases more hydroxide ions in solution, while sodium bicarbonate forms a buffer solution that resists large changes in pH.

9. How does sodium bicarbonate work as a leavening agent in baking?

Sodium bicarbonate works as a leavening agent by producing carbon dioxide gas when it reacts with acidic ingredients in the batter or dough. This gas forms bubbles, causing the mixture to rise and creating a light, airy texture in baked goods. Heat from baking accelerates this reaction and expands the gas bubbles further.

10. Why is sodium carbonate called "washing soda"?

Sodium carbonate is called "washing soda" due to its historical use in laundry and cleaning. Its alkaline nature helps to soften water and remove grease, making it effective for cleaning clothes and household surfaces. The term "soda" refers to its chemical nature as a sodium-containing compound.

11. Why is sodium carbonate used in glass manufacturing?

Sodium carbonate is used in glass manufacturing because it lowers the melting point of silica (sand), the main component of glass. This makes the glass-making process more energy-efficient. Additionally, sodium carbonate acts as a flux, helping to remove impurities and improve the quality of the glass.

12. What is the Solvay process, and how is it related to sodium carbonate?

The Solvay process is an industrial method for producing sodium carbonate on a large scale. It involves the reaction of sodium chloride (table salt) with ammonia and carbon dioxide in water, ultimately yielding sodium carbonate. This process revolutionized the production of sodium carbonate, making it more economical and widely available for various industrial applications.

13. How do sodium carbonate and sodium bicarbonate differ in their reaction with acids?

Both sodium carbonate and sodium bicarbonate react with acids, but sodium carbonate reacts more vigorously. Sodium carbonate can neutralize twice as much acid per mole compared to sodium bicarbonate. This is because sodium carbonate has two sodium ions that can be replaced by hydrogen ions from the acid, while sodium bicarbonate has only one.

14. How does the solubility of sodium carbonate compare to sodium bicarbonate?

Sodium carbonate is generally more soluble in water than sodium bicarbonate. At room temperature, the solubility of sodium carbonate is about 30g per 100mL of water, while sodium bicarbonate's solubility is about 10g per 100mL. This difference in solubility affects their applications and how they are used in various processes.

15. Why is sodium bicarbonate used in fire extinguishers?

Sodium bicarbonate is used in some fire extinguishers because it decomposes when heated, releasing carbon dioxide. This CO2 helps smother the fire by displacing oxygen. Additionally, the decomposition is endothermic, absorbing heat from the fire. The resulting sodium carbonate also forms a barrier on burning materials, helping to prevent reignition.

16. What role does sodium carbonate play in water treatment?

Sodium carbonate plays a crucial role in water treatment by helping to soften hard water. It reacts with calcium and magnesium ions in hard water, precipitating them as insoluble carbonates. This process, known as lime-soda softening, reduces water hardness, prevents scale formation in pipes and appliances, and improves the effectiveness of soaps and detergents.

17. How does sodium bicarbonate contribute to the "fizz" in effervescent tablets?

Sodium bicarbonate contributes to the "fizz" in effervescent tablets by reacting with a dry acid (like citric acid) when the tablet is dropped in water. This reaction produces carbon dioxide gas, creating the characteristic fizzing effect. The reaction only occurs when the tablet is dissolved, allowing for stable storage in dry form.

18. Why is sodium carbonate sometimes called "soda ash"?

Sodium carbonate is called "soda ash" due to its historical production method. It was originally obtained by burning specific plants that grew in sodium-rich soils, particularly those near the sea. The ashes of these plants were rich in sodium carbonate. Although modern production methods have changed, the name "soda ash" has persisted in industry.

19. How does the structure of sodium carbonate differ from sodium bicarbonate at the molecular level?

At the molecular level, sodium carbonate (Na2CO3) consists of two sodium ions (Na+) and one carbonate ion (CO3^2-). Sodium bicarbonate (NaHCO3) has one sodium ion (Na+) and one bicarbonate ion (HCO3^-). The key difference is the presence of a hydrogen atom in the bicarbonate ion, which affects the compound's properties and reactivity.

20. What is the environmental impact of sodium carbonate production?

The production of sodium carbonate, particularly through the Solvay process, can have environmental impacts. These include high energy consumption, CO2 emissions, and the generation of calcium chloride waste. However, modern production methods have improved efficiency and waste management. Sodium carbonate itself is not considered harmful to the environment when used properly.

21. How does sodium bicarbonate help in cleaning?

Sodium bicarbonate helps in cleaning due to its mild abrasive nature and its ability to neutralize odors and acids. It can gently scrub surfaces without scratching, absorb odors in refrigerators and carpets, and react with acidic substances to neutralize them. Its alkaline nature also helps to dissolve grease and dirt, making it an effective and environmentally friendly cleaning agent.

22. What happens when you mix vinegar with sodium bicarbonate?

When vinegar (acetic acid) is mixed with sodium bicarbonate, a vigorous reaction occurs. The acetic acid reacts with the bicarbonate, producing carbon dioxide gas, water, and sodium acetate. This reaction is often used in science demonstrations and cooking. The equation is: CH3COOH + NaHCO3 → CH3COONa + H2O + CO2.

23. How does sodium carbonate affect the freezing point of water?

Sodium carbonate, when dissolved in water, lowers its freezing point. This is due to the colligative properties of solutions, where the presence of dissolved particles interferes with the formation of ice crystals. The magnitude of the freezing point depression depends on the concentration of sodium carbonate in the solution.

24. Why is sodium bicarbonate used in some toothpastes?

Sodium bicarbonate is used in some toothpastes due to its mild abrasive and alkaline properties. It helps to gently remove stains and plaque from teeth without damaging enamel. Its alkaline nature also helps to neutralize acids in the mouth, which can contribute to tooth decay. Additionally, it can help freshen breath by neutralizing odor-causing compounds.

25. How does the thermal stability of sodium carbonate compare to sodium bicarbonate?

Sodium carbonate is more thermally stable than sodium bicarbonate. While sodium carbonate can withstand high temperatures without decomposing, sodium bicarbonate begins to break down at around 50°C, fully decomposing into sodium carbonate, water, and carbon dioxide at about 200°C. This difference in thermal stability affects their applications, particularly in cooking and industrial processes.

26. What is the role of sodium carbonate in the paper-making industry?

In the paper-making industry, sodium carbonate plays several important roles. It is used to adjust the pH of the pulp, helping to break down lignin and separate cellulose fibers. It also aids in the bleaching process by enhancing the effectiveness of hydrogen peroxide. Additionally, sodium carbonate helps in the de-inking process of recycled paper by making ink particles less sticky and easier to remove.

27. How does sodium bicarbonate affect the texture of baked goods?

Sodium bicarbonate affects the texture of baked goods by producing carbon dioxide gas when it reacts with acidic ingredients or heat. This gas forms bubbles in the batter or dough, which expand during baking, creating a light, airy texture. The amount and distribution of these bubbles significantly influence the final texture, making baked goods softer and less dense.

28. Why is sodium carbonate used in swimming pools?

Sodium carbonate is used in swimming pools to raise the pH and total alkalinity of the water. It helps to maintain the water's pH balance, preventing it from becoming too acidic, which can cause eye and skin irritation, as well as damage to pool equipment. Proper alkalinity also helps stabilize the pH, making it easier to maintain optimal water conditions.

29. How do sodium carbonate and sodium bicarbonate differ in their reaction with calcium ions?

Both sodium carbonate and sodium bicarbonate can react with calcium ions, but sodium carbonate reacts more completely. Sodium carbonate forms insoluble calcium carbonate precipitate, effectively removing calcium from solution. Sodium bicarbonate can also form calcium carbonate, but the reaction is less complete due to the equilibrium established in the solution, making it less effective at removing calcium ions.

30. What is the significance of sodium carbonate in the production of soaps and detergents?

Sodium carbonate is significant in soap and detergent production for several reasons. It acts as a builder, enhancing the cleaning power of the detergent by softening water and maintaining an alkaline pH. It also helps to emulsify oils and fats, making them easier to remove. In soap making, sodium carbonate can be used to convert fats into soap through saponification.

31. How does sodium bicarbonate contribute to the shelf-life of certain foods?

Sodium bicarbonate contributes to the shelf-life of certain foods by acting as a buffering agent. It helps maintain a stable pH, which can inhibit the growth of certain microorganisms. In baked goods, it can also help control moisture levels, further extending shelf life. However, its use must be balanced, as excessive amounts can affect taste and texture.

32. Why is sodium carbonate sometimes used in dyeing fabrics?

Sodium carbonate is used in dyeing fabrics because it creates an alkaline environment that helps open up the fibers, allowing the dye to penetrate more effectively. This is particularly useful for cotton and other cellulose-based fabrics. The alkaline conditions also help to fix the dye to the fabric, improving color fastness and durability.

33. How does the reactivity of sodium carbonate compare to potassium carbonate?

Sodium carbonate and potassium carbonate have similar chemical properties as they are both alkali metal carbonates. However, potassium carbonate is generally more reactive due to the higher reactivity of potassium compared to sodium. Potassium carbonate is more soluble in water and tends to be more hygroscopic (absorbs moisture from the air more readily) than sodium carbonate.

34. What role does sodium bicarbonate play in the body's pH buffering system?

Sodium bicarbonate plays a crucial role in the body's pH buffering system, particularly in blood. It forms part of the bicarbonate buffer system, which helps maintain blood pH within a narrow range (7.35-7.45). When the blood becomes too acidic, bicarbonate ions can accept hydrogen ions, forming carbonic acid, which can then be exhaled as CO2, thus helping to regulate blood pH.

35. How does the presence of sodium carbonate or sodium bicarbonate affect the boiling point of water?

The presence of sodium carbonate or sodium bicarbonate in water raises its boiling point. This is due to the colligative properties of solutions, where the dissolved particles interfere with the escape of water molecules into the vapor phase. Sodium carbonate, having more ions per molecule, will raise the boiling point more than an equal mass of sodium bicarbonate.

36. Why is sodium carbonate used in some hair relaxing treatments?

Sodium carbonate is used in some hair relaxing treatments due to its strong alkaline properties. It helps to break down the disulfide bonds in hair keratin, allowing the hair to be reshaped. The high pH also causes the hair shaft to swell, facilitating the penetration of the relaxing agents. However, its use must be carefully controlled to prevent hair damage.

37. How does sodium bicarbonate interact with stomach acid in the digestive system?

When sodium bicarbonate enters the stomach, it reacts with hydrochloric acid (HCl) to form sodium chloride, water, and carbon dioxide. The reaction is: NaHCO3 + HCl → NaCl + H2O + CO2. This neutralizes excess stomach acid, providing relief from heartburn and indigestion. However, the production of CO2 can cause bloating in some individuals.

38. What is the difference between anhydrous sodium carbonate and sodium carbonate decahydrate?

Anhydrous sodium carbonate (Na2CO3) contains no water molecules in its crystal structure, while sodium carbonate decahydrate (Na2CO3·10H2O) has ten water molecules associated with each sodium carbonate unit. The decahydrate form, also known as washing soda, has a lower sodium carbonate content by weight and different physical properties, such as a lower melting point.

39. How does sodium carbonate contribute to the production of glass?

Sodium carbonate is a crucial component in glass production. It acts as a flux, lowering the melting point of silica (the main component of glass) from about 1700°C to around 1500°C. This makes the glass-making process more energy-efficient. Sodium carbonate also helps to remove impurities and air bubbles from the molten glass, improving its quality and clarity.

40. Why is sodium bicarbonate sometimes used in agriculture?

Sodium bicarbonate is used in agriculture to adjust soil pH, particularly in alkaline soils. It can help neutralize acidic soils, improving nutrient availability for plants. It's also used as a fungicide to control powdery mildew on some plants. In livestock farming, it can be added to animal feed as a buffering agent to prevent acidosis in ruminants.

41. How does the crystal structure of sodium carbonate differ from that of sodium bicarbonate?

The crystal structure of sodium carbonate is monoclinic, with each sodium ion coordinated by six oxygen atoms from different carbonate ions. Sodium bicarbonate, on the other hand, has a monoclinic structure where each sodium ion is surrounded by one bicarbonate ion and five water molecules. These structural differences contribute to their distinct physical properties.

42. What is the role of sodium carbonate in the manufacture of synthetic detergents?

In the manufacture of synthetic detergents, sodium carbonate serves multiple purposes. It acts as a builder, enhancing the cleaning power of the detergent by softening water and maintaining an alkaline pH. It also helps to emulsify oils and suspend dirt particles. Additionally, sodium carbonate can be used to neutralize acids formed during the sulfonation process in detergent production.

43. How does sodium bicarbonate contribute to the leavening process in different types of baked goods?

Sodium bicarbonate contributes to leavening in baked goods by producing carbon dioxide gas. In recipes with acidic ingredients (like buttermilk or yogurt), it reacts immediately to produce gas. In recipes without acidic ingredients, it relies on heat to decompose and release CO2. The timing and rate of gas production affect the texture of different baked goods - for instance, quick breads versus cookies.

44. Why is sodium carbonate used in some water treatment processes?

Sodium carbonate is used in water treatment processes primarily for pH adjustment and water softening. It can raise the pH of acidic water, making it less corrosive to pipes and plumbing fixtures. In the lime-soda ash softening