Sodium Sulfide (Na2S): Structure, Molecular Mass, Properties and Uses

Sodium sulfide, or disodium monosulfide also known as Na₂S, is an inorganic chemical compound with the formula Na₂S. It has recently gained popularity in the organic chemical industry. When exposed to damp air, it produces a strong alkaline solution that smells like rotten eggs. The solution is colourless, despite the fact that the solid form is yellow. In the grades, it's generally referred to as "sodium sulfide flakes."

Read More: IUPAC Nomenclature of Organic Compounds

Key takeaways: sodium sufate, organic chemistry, disodium monosulfide, alkaline

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What Sodium Sulfide?

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Sodium sulfide is a salt that is used extensively in the organic chemistry sector. The chemical formula for sodium sulfide is Na₂S, or its hydrate, Na₂S₉H₂O. Anhydrous and hydrous salts are both colourless solids. Sodium sulfide is a highly alkaline, water-soluble chemical. When Na₂S and its hydrates are exposed to damp air, hydrogen sulfide is produced. This discharge has a rotten egg odour. Sodium sulfide in solution has a yellow solid form and is sold in grades known as sodium sulfide flakes. Disodium sulfide is the IUPAC designation for sodium sulfide. Sodium sulfide has an oxidation number of -2, and its pH is 10.4.

IUPAC Name – Sodium Sulfide

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Sodium Sulfide Structure – Na₂S

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The formula for sodium sulfide is Na₂S. 78.0452 g mol^-1 is the molar mass. A hydrated version of the salt (240.18 g mol^-1) is also available. Two sodium cations Na+ and one sulfur anion -2 make up the molecule. The structure has an antifluorite geometry, with eight-coordinate Na⁺ centres centered in a "box" for eight S−2 centres. This structure is created by swapping anions and cations' locations. This indicates that Na+ takes up fluoride sites, whereas S^2- takes up Ca²⁺ sites.

Read More: Difference between Cations and Anions

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Physical Properties on Sodium Sulfide - Na₂S

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Na2S also called sodium sulfide has a density of 1.86 g/cm³or 1.58 g mL^-1 in its pentahydrate form with a molecular weight or molar mass of 78.0452 g/mol, it has Autoignition temperature of > 480 °C (896 °F; 753 K). It has a Melting Point of 1,176° C (2,149° F).

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Chemical Data of Sodium Sulfide –Na₂S

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Na₂S has an Odour of rotten eggs. It has an appearance of Anhydrous yellow crystalline solids with a Storage temperature of 2-8°C and has a pH of 10.4. It has an oxidation number of -2 and it is insoluble in ether and is slightly soluble in alcohol. In water, sodium sulfide can undergo protonation, which means the sodium can be replaced by a proton in the reaction: S²⁻ + H⁺ → SH⁻

SH has a basic property that permits protonation to occur in aqueous solutions: SH⁻ + H₂O → SH₂ + OH^-

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Chemical Properties of Sodium sulfide – Na₂S

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• Sodium sulfide dissolves in water and forms the ions,The following is the reaction:- Na₂S + H₂O → 2 Na⁺ + HS^- + OH^-
• When heated, it quickly oxidized to generate sodium carbonate and sulfur dioxide. 2Na₂S + 3O₂ + 2CO₂ → 2Na₂CO₃ + 2SO₂
• Polysulfides are formed when it interacts with sulfur. 2Na₂S + S₈ → 2Na₂S₅
• Sodium sulfide is converted to sodium sulfate when it is oxidised by hydrogen peroxide. Na₂S + 4 H₂O₂ → 4 H₂O + Na₂SO₄

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Preparation of Sodium Sulfide

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A carbothermic reduction process produces Na₂S in industries. Carbon is employed as a reducing agent in this reduction process.Sodium sulfide is made by reducing sodium sulfate with coal at temperatures exceeding 950 degrees Celsius: 

Na₂SO₄ + 2 C → Na₂S + 2 CO₂

The reduction process is commonly used in labs to make sodium sulfide salt. With the aid of naphthalene as a catalyst, sodium sulfide is reacted with anhydride ammonia or sodium in dry THF. Sodium naphthalenide will be the end product.

2Na + S → Na₂S

The reaction between sodium carbonate and barium sulfide is a second technique.

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Uses of Sodium Sulfide – Na₂S

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• It is employed as an oxygen scavenger and a metal precipitant in water treatment.
•  Sodium hydroxide and sodium sulfide are used to dissolve the lignin in wood fibre.
• To tone black and white photos in chemical photography, sodium sulfide is utilized as a metal precipitant.
• It's used to make elastomeric synthetic materials, sulfur colors, and other things.
• In the craft process, it's mostly used in the pulp and paper sector. It improves the sulfate cooking process' selectivity and speeds up the delignification process..
• Sodium sulfide is employed as a bleaching, dechlorinating, and desulphurising chemical in the textile business.
• Sulfur dyes and other chemical compounds are utilized in the manufacturing of rubber chemicals.
• Ore flotation, dyeing, oil recovery, and detergent are just a few of the uses.

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Safety Precautions

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• Use as an unhairing agent in the liming process during the leather manufacturing process.
• Skin burns are caused by sodium sulfide, which is a strong alkaline.
• When sodium sulfide reacts swiftly with acid, deadly hydrogen sulfide is formed.

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Harmful Effects of Sodium Sulfide

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It's natural for the top layer of skin to peel. Skin irritation, redness, and scaling are other potential adverse effects. If any of these symptoms continue or worsen, stop taking this medicine and contact your doctor or pharmacist straight once.Remember that your doctor prescribed this medicine because the benefits to you outweigh the risks of side effects. The majority of people who use this medication experience no significant side effects.Sodium sulfide is an alkaline substance. It can result in severe skin burns. When acid reacts with water, hydrogen sulfide is formed, which is a very dangerous and combustible gas. Hydrogen sulfide builds at the bottom of areas with limited ventilation. To utilize hydrogen sulfide, one should keep the safety data sheet with them.

Na₂S + 2HCl → 2NaCl + H₂S(g)

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Things to Remember

• Sodium sulfide, also known as disodium monosulfide, is an inorganic substance.
• When exposed to damp air, it produces a strong alkaline solution that smells like rotten eggs.
• it's generally referred to as "sodium sulfide flakes."
• Sodium sulfide has an oxidation number of -2,
• its pH level is 10.4.
• It has an oxidation number of -2.
• sodium sulfide can undergo protonation, which means the sodium can be replaced by a proton.
• It is insoluble in ether and is slightly soluble in alcohol. 
• Sodium sulfide is a highly alkaline, water-soluble chemical.
• When acid reacts with water, hydrogen sulfide is formed, which is a very dangerous and combustible gas.
• Hydrogen sulfide builds at the bottom of areas with limited ventilation.
• This chemical is highly utilized in the paper, water, and textile industries.