Sodium phosphate dibasic or Na2HPO4 is a compound commonly used as a buffering agent in laboratory settings. It can also be found in some food and beverage products as a food additive.
| IUPAC Name | Disodium hydrogen phosphate |
| Molecular Formula | Na2HPO4 |
| CAS Number | 7558-79-4 |
| Synonyms | Sodium hydrogen phosphate, Disodium phosphate, Dibasic sodium phosphate, Sodium phosphate dibasic anhydrous, Sodium phosphate dibasic heptahydrate |
| InChI | InChI=1S/2Na.H3O4P/c;;1-5(2,3)4/h;;(H3,1,2,3,4)/q2*+1;/p-2 |
Na2HPO4 molar mass
The molar mass of sodium phosphate dibasic is 141.96 g/mol. This value is calculated by adding up the atomic masses of each of the elements present in the compound, which are sodium (Na), phosphorus (P), and oxygen (O). The molar mass is an important parameter that is used in various calculations, such as in determining the amount of a substance needed to carry out a reaction or to make a solution of a certain concentration.
Disodium Phosphate formula
The chemical formula of sodium phosphate dibasic is Na2HPO4. This formula represents the ratio of each of the elements present in the compound. The formula is important in determining the chemical properties of the compound, such as its reactivity and solubility.
Sodium phosphate dibasic boiling point
Sodium phosphate dibasic does not have a definite boiling point because it decomposes before reaching its boiling point. However, the decomposition temperature of sodium phosphate dibasic is reported to be around 155°C. At temperatures above this value, the compound starts to break down into its constituent ions, sodium and phosphate. This property makes it unsuitable for use in applications that require heating to high temperatures.
Sodium phosphate dibasic melting point
The melting point of Na2HPO4 varies depending on the form in which it is present. The anhydrous form of the compound has a melting point of 358°C, while the heptahydrate form has a lower melting point of 93°C. The melting point is an important physical property that is used to identify and characterize substances.
Sodium phosphate dibasic density g/ml
The density of Na2HPO4 depends on the form in which it is present. The anhydrous form of the compound has a density of 1.7 g/mL, while the heptahydrate form has a lower density of 1.68 g/mL. Density is a physical property that describes how much mass is contained in a certain volume of a substance.
Sodium phosphate dibasic molecular weight
The molecular weight of Na2HPO4 is 141.96 g/mol. This value is calculated by adding up the atomic masses of each of the elements present in the compound. Molecular weight is an important parameter that is used in various calculations, such as in determining the amount of a substance needed to carry out a reaction or to make a solution of a certain concentration.
Sodium phosphate dibasic Structure
Na2HPO4 has a crystalline structure. The anhydrous form of the compound is a white, odorless powder, while the heptahydrate form is a colorless, transparent crystal. The compound has a tetrahedral shape around the phosphorus atom, with each oxygen atom at the corners of the tetrahedron. The sodium ions are located in the interstitial spaces between the tetrahedra.
| Appearance | White powder or transparent crystals |
| Specific Gravity | 1.68 – 1.7 g/mL |
| Color | Colorless to white |
| Odor | Odorless |
| Molar Mass | 141.96 g/mol |
| Density | 1.68 – 1.7 g/mL |
| Melting Point | Anhydrous: 358°C, Heptahydrate: 93°C |
| Boiling Point | Decomposes before boiling |
| Flash Point | Not applicable |
| Water Solubility | Highly soluble |
| Solubility | Soluble in water, insoluble in ethanol |
| Vapour Pressure | Not applicable |
| Vapour Density | Not applicable |
| PKa | 2.15 (Phosphate ion) |
| PH | 8.0 – 11.0 (0.1 M aqueous solution) |
Sodium Phosphate Dibasic Safety and Hazards
Sodium phosphate dibasic (Na2HPO4) is generally considered to be safe for use in various applications, but it can cause skin and eye irritation. Inhaling the compound in powder form may cause respiratory irritation. Na2HPO4 may react violently with strong acids and oxidizing agents, and it can release toxic fumes when heated to high temperatures. As with all chemicals, appropriate precautions should be taken when handling this compound, such as wearing protective clothing and gloves and working in a well-ventilated area. In case of contact with skin or eyes, rinse with plenty of water and seek medical attention if necessary.
| Hazard Symbols | None |
| Safety Description | S22 – Do not breathe dust, S24 – Avoid contact with skin, S37 – Wear suitable gloves |
| UN Ids | UN3077 |
| HS Code | 28352200 |
| Hazard Class | 9 |
| Packing Group | III |
| Toxicity | LD50 (rat, oral) – 3,400 mg/kg |
Sodium Phosphate Dibasic Synthesis Methods
Sodium phosphate dibasic (Na2HPO4) can be synthesized through several methods, including reacting phosphoric acid with sodium hydroxide, neutralizing phosphoric acid with sodium carbonate or bicarbonate, and reacting sodium phosphate monobasic with sodium hydroxide.
- One common method involves reacting phosphoric acid with sodium hydroxide in a 1:2 ratio to produce Na2HPO4 and water. The reaction can be carried out at room temperature or under gentle heating, and the resulting product is purified through crystallization or evaporation.
- Another method involves neutralizing phosphoric acid with sodium carbonate or bicarbonate, followed by precipitation of the Na2HPO4. The pH of the reaction mixture is adjusted to around 8-9 using sodium carbonate or bicarbonate, and the resulting precipitate is collected and washed with water to remove any impurities.
- A third method involves reacting sodium phosphate monobasic with sodium hydroxide in a 1:1 ratio, resulting in the formation of Na2HPO4 and water. The resulting product is then purified through crystallization or evaporation.
The choice of method depends on factors such as the desired purity, yield, and cost-effectiveness. The synthesis of Na2HPO4 can be achieved through several methods, each with its own advantages and limitations.
Sodium Phosphate Dibasic Uses
Sodium phosphate dibasic finds wide applications in different industries.
- The food industry uses it as an emulsifier, buffer, and thickening agent. It acts as a sequestrant, helping to preserve the quality and stability of food by preventing metal ions from reacting with other food components. It serves as a leavening agent in baking powders and as a pH adjuster in dairy products.
- The medical industry uses it as a laxative to treat constipation by increasing water content in the colon. It is also used in the preparation of medications and injections as a pH adjuster and buffer.
- In the agriculture industry, it acts as a fertilizer, providing phosphorus for plants.
- It also works as a nutrient supplement in animal feed.
- The water treatment industry uses Na2HPO4 as a corrosion inhibitor and scale inhibitor in boilers and cooling systems.
- It works as a cleaning agent, removing calcium and magnesium deposits from surfaces.
Questions:
Q: Is sodium phosphate dibasic a preservative?
A: Na2HPO4 is not typically used as a preservative in food products. However, it can act as a sequestrant, which can help to preserve the quality and stability of food by preventing metal ions from reacting with other food components.
Q: How many moles of sodium phosphate, dibasic ( m.w. 141.98) are in 50 ml of a 20% w/v solution?
A: To calculate the number of moles in a 20% w/v solution of Na2HPO4, we first need to convert the percentage weight/volume to grams/100 mL. 20% w/v solution means 20 grams of the compound in 100 mL of solution. Therefore, 50 mL of the solution contains 10 grams of Na2HPO4. To calculate the number of moles, we divide the mass by the molecular weight:
moles = mass / molecular weight moles = 10 g / 141.98 g/mol moles = 0.070 moles
Therefore, there are 0.070 moles of Na2HPO4 in 50 mL of a 20% w/v solution.
Q: What is the density of sodium phosphate dibasic?
A: The density of Na2HPO4 depends on the form and concentration of the compound. The anhydrous form has a density of approximately 2.36 g/cm³, while the heptahydrate form has a density of approximately 1.62 g/cm³. In solution, the density will vary depending on the concentration.