Sodium Phosphate (Na3PO4) - Structure, Molecular Mass, FAQs

Q: What is sodium phosphate and write sodium phosphate formula.

Sodium phosphate is a salt formed when sodium (Na + ) and phosphate (PO 4 3− ) ions combine. Sodium phosphate and its salt may exist in hydrated or anhydrous form. Commonly known as phospho soda, is saline purgative (purgative is a medicine for better digestion). Sodium phosphate or its other forms are produced when hydrogen atom(s) in phosphoric acid (H 3 PO 4 ) are replaced by sodium atoms. Removal of one hydrogen atom forms monobasic form of sodium phosphate, removal of two hydrogen atoms forms dibasic form of sodium phosphate and removal of all hydrogen atoms forms tribasic form of sodium phosphate. Being a salt, sodium phosphate and its other forms are crystalline solids or white powders. They are colorless to white in appearance. Sodium phosphate chemical formula is Na 3 PO 4 .

Q: Write name of Na2HPO4 and Na3PO4.

Na 2 HPO4 name is Disodium phosphate and Na 3 PO 4 compound name is trisodium phosphate.

Q: Is Na3PO4 acid or base?

Na 2 PO 4 , trisodium phosphate is slightly acidic in nature based on its pKa value.

Q: Na3PO4 is which type of salt?

Na 3 PO 4 is phosphate salt of sodium.

Q: Is Na2HPO4 acid or base?

Na 2 HPO 4 , monosodium phosphate is neutral that is neither acid nor base.

Q: Write sodium phosphide formula.

Sodium phosphide formula is Na 3 P.

Sodium Phosphate (Na3PO4) - Structure, Molecular Mass, FAQs

Edited By Team Careers360 | Updated on Jul 02, 2025 04:51 PM IST

What is sodium phosphate?

Sodium phosphate is a salt formed when sodium (Na⁺) and phosphate (PO₄³⁻) ions combine. Sodium phosphate formula is Na₃PO₄. Sodium phosphate and its salt may exist in hydrated or anhydrous form. Commonly known as phospho soda, is saline purgative (purgative is a medicine for better digestion). Sodium phosphate or its other forms are produced when hydrogen atom(s) in phosphoric acid (H₃PO₄) are replaced by sodium atoms. Removal of one hydrogen atom forms monobasic form of sodium phosphate, removal of two hydrogen atoms forms dibasic form of sodium phosphate and removal of all hydrogen atoms forms tribasic form of sodium phosphate. Being a salt, sodium phosphate and its other forms are crystalline solids or white powders. They are colorless to white in appearance.

This Story also Contains

What is sodium phosphate?
Family of sodium phosphate
Sodium phosphate uses
Effects of sodium phosphate

Na3PO4 structure

Figure 1 Na₃PO₄ structure.

Sodium phosphate is also known as sodium orthophosphate, tribasic sodium phosphate, trisodium phosphate. Density of trisodium phosphate is 1.62 g/cm³. Sodium phosphate molecular weight (or molar mass of sodium phosphate) is 163.94 g/mol.

Boiling point of sodium phosphate is 100 °C and the melting point of sodium phosphate is 1,583 °C. The value of trisodium phosphate solubility is ‘soluble in water’.

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Family of sodium phosphate

Monophosphates

Sodium monophosphate salts are mostly derived from orthophosphate (PO₄³⁻), dihydrogen phosphate (H2PO₄⁻) and hydrogen phosphate (HPO₄²⁻).

Some name and the formula of different sodium phosphate is given below.

monosodium phosphate (anhydrous) NaH₂PO₄ ,disodium phosphate (anhydrous)Na₂HPO₄, disodium phosphate (dihydrate) HNa₂PO₄(H₂O)₂, disodium phosphate (heptahydrate)HNa₂PO₄(H₂O)₇, monosodium phosphate (monohydrate) NaH₂PO₄(H₂O), monosodium phosphate (dihydrate) NaH₂PO₄(H₂O)₂, disodium phosphate (octahydrate) HNa₂PO₄(H₂O)₈, disodium phosphate (dodecahydrate) HNa₂PO₄(H₂O)₁₂,

Diphosphates and polyphosphates

A number of important salts are produced when sodium reacts with pyrophosphates; also known as Diphosphates, triphosphates and high polymers.

Some name and formula are given below.

monosodium diphosphate (anhydrous) NaH₃P₂O₇, disodium diphosphate (hexahydrate) Na₂H₂P₂O₇(H₂O)₆, trisodium diphosphate (anhydrous) Na₃HP₂O₇, trisodium diphosphate (monohydrate) Na₃HP₂O₇(H₂O), disodium diphosphate (anhydrous) Na₂H₂P₂O₇, trisodium diphosphate (nonahydrate) Na₃HP₂O₇(H₂O)₉, tetrasodium diphosphate (decahydrate) Na₄P₂O₇(H₂O)₁₀

Triphosphate salts of sodium like tetraphosphates and sodium triphosphate are also known. Metaphosphates, a name given to cyclic phosphates such as Na₃P₃O₉ trimer sodium trimetaphosphate and tetramer Na₄P₄O₁₂ also exist.

When NaH₂PO₄ and Na₂HPO₄ are heated, polymeric sodium phosphates are formed. To form a specific polyphosphate annealing and heating process is altered. Some of such specific polyphosphate is Graham’s salt, Kurrol’s salt and Maddrell’s salt. Graham salt has a formula NaO(NaPO₃)Na₂. Kurrol’s salt and Maddrell’s salt has a general formula [NaPO₃]n[NaPO₃(OH)]₂ where n can have a value upto 2000. . Kurrol’s salt and Maddrell’s salt are crystalline polyphosphates with a high molecular weight.

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Sodium phosphate uses

Sodium phosphate and its other forms are very commonly used in a lot of everyday products. This is because sodium phosphate is inexpensive and is nontoxic when taken in adequate amounts. Some sodium phosphate uses includes:

Sodium phosphate is used in food and water treatment.
Sodium phosphate is used as an emulsifier in processed cheese production.
Sodium phosphate is used as a thickening agent in soups, etc.
Sodium phosphate is used as a leavening agent for baked food.
Sodium phosphate is used to control pH of processed food.
Sodium phosphate is used as medicine for constipation.
Sodium phosphate is used as pharmaceuticals to prepare the bowel for further medical processes.
Sodium phosphate is used in detergents for the purpose of softening hard water
Sodium phosphate is used in anti-rust solutions as an efficient solution.
Sodium phosphate is used in fertilizers
Sodium phosphate is used in animal food as preservative
Sodium phosphate is used in soaps.
Sodium phosphate is used as a food additive.
Sodium phosphate particularly disodium pyrophosphate is often used as a buffer.
Sodium phosphate is used in toothpaste to remove magnesium from saliva which prevents cavities and plaques.

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Effects of sodium phosphate

As discussed, sodium phosphate is used in bowel preparation for medical procedures like colonoscopy. High levels of sodium phosphate intake carries a hazardous risk of kidney failure. Sodium phosphates also play a major role in eutrophication of water. Eutrophication involves increased algal growth known as algal bloom due to presence of excess phosphate which in turn causes decreased oxygen levels in water. Sodium phosphates generally reach water bodies like ponds, rivers or lakes by washing off detergents, soaps, factories or fertilizers.

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NCERT Chemistry Notes:

Frequently Asked Questions (FAQs)

1. What is sodium phosphate and write sodium phosphate formula.

Sodium phosphate is a salt formed when sodium (Na⁺) and phosphate (PO₄³⁻) ions combine. Sodium phosphate and its salt may exist in hydrated or anhydrous form. Commonly known as phospho soda, is saline purgative (purgative is a medicine for better digestion). Sodium phosphate or its other forms are produced when hydrogen atom(s) in phosphoric acid (H₃PO₄) are replaced by sodium atoms. Removal of one hydrogen atom forms monobasic form of sodium phosphate, removal of two hydrogen atoms forms dibasic form of sodium phosphate and removal of all hydrogen atoms forms tribasic form of sodium phosphate. Being a salt, sodium phosphate and its other forms are crystalline solids or white powders. They are colorless to white in appearance. Sodium phosphate chemical formula is Na₃PO₄.

2. Write name of Na2HPO4 and Na3PO4.

Na₂HPO4 name is Disodium phosphate and Na₃PO₄ compound name is trisodium phosphate.

3. Is Na3PO4 acid or base?

Na₂PO₄, trisodium phosphate is slightly acidic in nature based on its pKa value.

4. Write Na3PO4 molar mass.

Sodium phosphate molecular weight (or molar mass of sodium phosphate) is 163.94 g/mol.

5. Na3PO4 is which type of salt?

Na₃PO₄ is phosphate salt of sodium.

6. Is Na2HPO4 acid or base?

Na₂HPO₄, monosodium phosphate is neutral that is neither acid nor base.

7. Write sodium phosphide formula.

Sodium phosphide formula is Na₃P.

8. Write PO4 molar mass.

Molecular weight of phosphate is 94.971361 g/mol. It can be calculated by adding molecular weight of phosphorus (molecular weight of one P atom is 30.973761 g/mol) and molecular weight of four oxygen atoms (molar mass of one oxygen is 15.9994 g/mol).

9. Write sodium phosphate enema bp uses.

Sodium phosphate enema bp uses are:

Sodium phosphate enema is used to treat constipation.
Sodium phosphate enema is used to clean the gastrointestinal tract usually before colonoscopy.

10. Write sodium phosphate monobasic molecular weight.

sodium phosphate monobasic molecular weight is 119.98 g/mol.

11. Write adverse effects of sodium phosphate.

12. What is the pH of a sodium phosphate solution?

A sodium phosphate (Na3PO4) solution is basic, with a pH greater than 7. This is because the phosphate ion (PO4^3-) is a strong base that accepts protons from water, producing hydroxide ions and increasing the pH.

13. How does temperature affect the solubility of sodium phosphate?

Like most solid solutes in water, the solubility of sodium phosphate generally increases with temperature. This is because higher temperatures provide more energy for the dissolution process, allowing more solute particles to overcome the lattice energy and enter the solution.

14. What is the role of sodium phosphate in biological systems?

Sodium phosphate plays crucial roles in biological systems. It's a component of DNA and RNA, helps maintain pH balance in cells, and is involved in energy transfer through ATP (adenosine triphosphate). It's also important for bone and tooth formation.

15. How does sodium phosphate contribute to water hardness?

Unlike calcium or magnesium phosphates, sodium phosphate does not contribute to water hardness. In fact, it's sometimes used as a water softener because the phosphate ions can bind to calcium and magnesium ions, preventing them from forming scale.

16. How does sodium phosphate act as a buffer?

Sodium phosphate can act as a buffer due to the ability of the phosphate ion to accept or donate protons. In solution, it can exist in different forms (H3PO4, H2PO4^-, HPO4^2-, PO4^3-) which can neutralize small amounts of added acid or base, maintaining a relatively stable pH.

17. What is the difference between monosodium, disodium, and trisodium phosphate?

These terms refer to the number of sodium atoms in the phosphate compound. Monosodium phosphate (NaH2PO4) has one sodium atom, disodium phosphate (Na2HPO4) has two, and trisodium phosphate (Na3PO4) has three. They differ in their pH and reactivity.

18. What is the difference between anhydrous and hydrated forms of sodium phosphate?

Anhydrous sodium phosphate (Na3PO4) contains no water molecules in its crystal structure, while hydrated forms (like Na3PO4·12H2O) include water molecules. The hydrated forms have different physical properties, such as lower melting points, and may behave differently in chemical reactions.

19. What is the oxidation state of phosphorus in sodium phosphate?

In sodium phosphate (Na3PO4), the oxidation state of phosphorus is +5. This can be determined by considering that sodium has an oxidation state of +1, oxygen has -2, and the overall compound is neutral.

20. What is the crystal structure of sodium phosphate?

Sodium phosphate typically crystallizes in a monoclinic crystal system. In this structure, the sodium ions and phosphate ions are arranged in a repeating pattern that gives the crystal its characteristic shape and properties.

21. How does the solubility of sodium phosphate compare to other sodium salts?

Sodium phosphate is highly soluble in water, like many sodium salts. However, its solubility is generally lower than that of sodium chloride or sodium nitrate. The larger size and higher charge of the phosphate ion compared to chloride or nitrate ions affect its solubility.

22. What are the industrial uses of sodium phosphate?

Sodium phosphate has various industrial applications. It's used in detergents as a water softener, in food processing as an emulsifier and pH regulator, in water treatment to prevent corrosion and scale formation, and in ceramics manufacturing.

23. How does sodium phosphate interact with calcium ions?

Sodium phosphate readily reacts with calcium ions to form calcium phosphate, which is insoluble. This property is utilized in water softening and in preventing scale formation in pipes. However, it can also lead to the formation of kidney stones in the body.

24. How does sodium phosphate contribute to the flavor of processed foods?

Sodium phosphate is used as a food additive (E339) and can contribute to flavor in several ways. It acts as a pH buffer, which can affect taste perception. It also enhances the binding of water molecules, which can improve texture and mouthfeel in processed meats and cheeses.

25. How does sodium phosphate dissolve in water?

When sodium phosphate dissolves in water, it dissociates into its constituent ions. The Na+ ions and PO4^3- ions separate and become surrounded by water molecules in a process called hydration. This dissociation is what makes sodium phosphate a good electrolyte.

26. How does the reactivity of sodium phosphate compare to other sodium compounds?

Sodium phosphate is generally less reactive than sodium compounds with monatomic anions like sodium chloride. This is due to the larger size and higher charge of the phosphate ion, which makes it more stable. However, it's more reactive in certain contexts, such as its ability to form complexes with metal ions.

27. What is the chemical formula of sodium phosphate?

The chemical formula of sodium phosphate is Na3PO4. This formula represents three sodium (Na) atoms bonded to one phosphate (PO4) group.

28. Why is sodium phosphate considered an s-block compound?

Sodium phosphate is considered an s-block compound because sodium (Na) is an s-block element. S-block elements are found in the first two groups of the periodic table and have their outermost electrons in the s orbital.

29. What is the molecular mass of sodium phosphate?

The molecular mass of sodium phosphate (Na3PO4) is approximately 163.94 g/mol. This is calculated by summing the atomic masses of 3 sodium atoms (22.99 g/mol each), 1 phosphorus atom (30.97 g/mol), and 4 oxygen atoms (16.00 g/mol each).

30. Is sodium phosphate ionic or covalent?

Sodium phosphate is an ionic compound. It consists of positively charged sodium ions (Na+) and negatively charged phosphate ions (PO4^3-). The strong electrostatic attraction between these ions forms the ionic bond.

31. How does the structure of sodium phosphate differ from sodium chloride?

While both are ionic compounds, sodium phosphate (Na3PO4) has a more complex structure than sodium chloride (NaCl). In Na3PO4, there are three sodium ions for every one phosphate ion, whereas in NaCl, there is a 1:1 ratio of sodium to chloride ions. The phosphate ion is also polyatomic, unlike the monatomic chloride ion.

32. What is the environmental impact of sodium phosphate?

While sodium phosphate itself is not toxic, its overuse can lead to environmental issues. When it enters water bodies, it can cause eutrophication - excessive nutrient enrichment that leads to algal blooms, depleting oxygen in the water and harming aquatic life.

33. What is the effect of sodium phosphate on protein solubility?

Sodium phosphate can affect protein solubility in various ways. At low concentrations, it can increase protein solubility by increasing the ionic strength of the solution. At higher concentrations, it can cause "salting out" where proteins precipitate due to competition for water molecules.

34. What is the role of sodium phosphate in DNA extraction?

Sodium phosphate is often used in DNA extraction protocols. It helps to maintain a stable pH and also aids in lysing cells by disrupting cell membranes. The phosphate groups in the buffer also compete with DNA phosphate groups for binding to proteins, helping to purify the DNA.

35. How does sodium phosphate affect the freezing point of water?

Like other dissolved salts, sodium phosphate lowers the freezing point of water. This is due to the colligative properties of solutions, where the presence of dissolved particles interferes with the formation of ice crystals, requiring a lower temperature for freezing to occur.

36. How does sodium phosphate act as a sequestering agent?

Sodium phosphate acts as a sequestering agent by forming stable complexes with metal ions like calcium and magnesium. This property is useful in water treatment and detergents, where it prevents these ions from interfering with cleaning processes or forming scale.

37. What is the role of sodium phosphate in fertilizers?

Sodium phosphate can be used in fertilizers as a source of phosphorus, an essential nutrient for plant growth. However, it's less common than other phosphate fertilizers due to its high sodium content, which can be detrimental to soil health in large quantities.

38. How does the presence of sodium phosphate affect the boiling point of water?

The presence of dissolved sodium phosphate raises the boiling point of water. This is another colligative property of solutions, where the dissolved ions interfere with the escape of water molecules into the gas phase, requiring more energy (higher temperature) for boiling to occur.

39. What is the difference between organic and inorganic phosphates?

Sodium phosphate is an inorganic phosphate, meaning it doesn't contain carbon-hydrogen bonds. Organic phosphates, on the other hand, contain carbon and are often found in biological molecules like DNA and ATP. Inorganic phosphates like sodium phosphate are generally more stable and less complex.

40. How does sodium phosphate compare to potassium phosphate in terms of properties and uses?

Sodium phosphate and potassium phosphate have similar chemical properties due to the similarity of sodium and potassium as alkali metals. However, potassium phosphate is often preferred in biological applications and fertilizers because potassium is an essential nutrient for living organisms and plants, while excessive sodium can be harmful.

41. What is the role of sodium phosphate in meat processing?

In meat processing, sodium phosphate is used as a food additive to improve water retention, texture, and shelf life. It helps to bind water molecules, reducing moisture loss during cooking and storage. This can improve the juiciness and tenderness of processed meats.

42. How does sodium phosphate affect the viscosity of solutions?

Sodium phosphate can increase the viscosity of solutions, particularly at higher concentrations. This is due to the interactions between the phosphate ions and water molecules, as well as potential interactions with other dissolved species. This property is utilized in some food and industrial applications.

43. What is the difference between orthophosphates and condensed phosphates?

Sodium phosphate (Na3PO4) is an orthophosphate, containing a single phosphorus atom surrounded by four oxygen atoms. Condensed phosphates, like sodium pyrophosphate (Na4P2O7), contain multiple phosphorus atoms linked by oxygen bridges. Condensed phosphates often have different properties and applications compared to orthophosphates.

44. How does sodium phosphate interact with proteins in food products?

Sodium phosphate can interact with proteins in several ways. It can affect protein solubility and stability by altering the pH and ionic strength of the solution. It can also bind to certain amino acid residues in proteins, potentially affecting their structure and function. In meat products, it can improve water retention and texture by interacting with muscle proteins.

45. What is the role of sodium phosphate in toothpaste?

In toothpaste, sodium phosphate serves multiple purposes. It acts as a buffering agent to control pH, helps to remineralize tooth enamel by providing phosphate ions, and can act as a mild abrasive to help remove plaque and stains. Some forms of sodium phosphate also have antimicrobial properties.

46. How does sodium phosphate affect the growth of microorganisms?

Sodium phosphate can affect microbial growth in various ways. As a source of phosphorus, it can promote growth of some microorganisms. However, at high concentrations, it can inhibit growth due to osmotic effects. Its ability to sequester metal ions can also affect microbial growth by altering the availability of essential minerals.

47. What is the difference between food-grade and technical-grade sodium phosphate?

Food-grade sodium phosphate meets strict purity standards set by food regulatory agencies and is safe for consumption. Technical-grade sodium phosphate may contain impurities and is used for industrial applications where human consumption is not a concern. The production processes and quality control measures are typically more stringent for food-grade products.

48. How does sodium phosphate contribute to the shelf life of processed foods?

Sodium phosphate contributes to food preservation in several ways. It acts as a pH buffer, helping to maintain a stable acidity level that can inhibit microbial growth. It also sequesters metal ions that could catalyze oxidation reactions, thus preventing rancidity in fats. Additionally, its water-binding properties can help maintain texture and prevent moisture loss.

49. What is the role of sodium phosphate in fire extinguishers?

Some dry chemical fire extinguishers use sodium phosphate compounds. When heated, these compounds release water vapor and form a glassy coating on the burning material, smothering the fire and preventing re-ignition. The phosphate also acts as a heat sink, absorbing thermal energy from the fire.

50. How does sodium phosphate affect the gelation of starch?

Sodium phosphate can affect starch gelation by altering the pH and ionic environment. It can promote starch swelling and gelatinization at lower temperatures. However, at high concentrations, it may inhibit gelation by competing with starch molecules for water. This property is utilized in food processing to control texture and consistency.

51. What is the difference between sodium phosphate and calcium phosphate in terms of solubility?

Sodium phosphate is generally much more soluble in water than calcium phosphate. This is due to the stronger ionic bond between calcium and phosphate ions compared to sodium and phosphate ions. The lower solubility of calcium phosphate is significant in biological systems, where it forms the mineral component of bones and teeth.

52. How does sodium phosphate affect the color of meat products?

Sodium phosphate can indirectly affect meat color by influencing pH and water retention. A higher pH can result in a darker, more appealing color in fresh meat. In cured meats, phosphates can enhance the development and stability of the characteristic pink color by interacting with myoglobin and nitrites.

53. What is the role of sodium phosphate in cheese production?

In cheese production, sodium phosphate can be used as an emulsifying salt. It helps to disperse proteins and fats, creating a smooth, uniform texture in processed cheeses. It also contributes to moisture retention and can prevent the separation of fats during heating.

54. How does sodium phosphate affect the hardness of water?

Sodium phosphate acts as a water softener by sequestering calcium and magnesium ions, which are responsible for water hardness. When added to hard water, sodium phosphate forms soluble complexes with these ions, effectively reducing water hardness without forming precipitates.

55. What is the difference between sodium phosphate and sodium polyphosphate?

Sodium phosphate (Na3PO4) is a simple orthophosphate with one phosphorus atom. Sodium polyphosphate consists of multiple phosphate units linked together. Polyphosphates generally have stronger sequestering properties and are more effective at dispersing proteins and minerals, making them useful in various industrial and food applications.

56. How does sodium phosphate affect the pH of blood?

Sodium phosphate plays a crucial role in maintaining blood pH as part of the body's phosphate buffer system. The balance between HPO4^2- and H2PO4^- acts to neutralize small changes in pH, helping to keep blood pH within the narrow range necessary for proper physiological function.

57. What is the role of sodium phosphate in ceramics manufacturing?

In ceramics manufacturing, sodium phosphate can be used as a deflocculant. It helps to disperse clay particles in water, reducing viscosity and improving the flow properties of ceramic slips. This allows for better mold filling and can improve the quality of the final ceramic product.

58. How does sodium phosphate compare to ammonium phosphate as a fertilizer?

While both provide phosphorus for plant growth, ammonium phosphate is generally preferred as a fertilizer. It provides both nitrogen and phosphorus, two essential plant nutrients. Sodium phosphate, while a good source of phosphorus, contains sodium which can accumulate in soil and harm plants if used excessively.

59. What is the role of sodium phosphate in the production of synthetic detergents?

In detergent production, sodium phosphate serves multiple functions. It acts as a builder, enhancing the cleaning power of surfactants by sequestering hard water ions. It also helps to maintain an alkaline pH, which aids in removing acidic soils. Additionally, it can help to suspend dirt particles, preventing them from redepositing on cleaned surfaces.

60. How does sodium phosphate affect the freezing and thawing stability of food products?

Sodium phosphate can improve the freeze-thaw stability of food products. It helps to bind water, reducing ice crystal formation during freezing. This can help maintain the texture and quality of foods after thawing.