How Does Sodium Sulfide Behave Chemically?
Sodium sulfide, or Na2S, is an inorganic chemical compound with the formula of Na2S that has risen to prominence in the organic chemical industry. It's a powerful alkaline solution that smells like rotten eggs when exposed to moist air. Despite the fact that the solid-state is yellow, the solution is colourless. It's usually labelled as "sodium sulfide flakes" in the grades.
Sodium sulfide is a salt which plays an essential role in the organic chemistry industry. The formula for sodium sulfide is Na2S, or more commonly its hydrate Na2S·9H2O. Both the anhydrous and the hydrous salts are colourless solids. Sodium sulfide is a water-soluble compound, with a strongly alkaline solution. If the compound is exposed in the moist air, Na2S and its hydrates emit hydrogen sulfide. This emission smells like a rotten egg. The solid-state of sodium sulfide in solution is a yellow colour, and it comes as grades, known as sodium sulfide flakes. The IUPAC name of sodium sulfide is disodium sulfide. The oxidation number of sodium sulfide is -2, whereas its pH value is 10.4.
IUPAC Name – Sodium Sulfide
Sodium Sulfide Structure – Na2S
Na2S adopts the antifluorite structure. This structure is obtained by exchanging the positions of anions and cations. This means that the Na+ occupy sites of the fluoride and S2- hold the sites for Ca2+.
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Sodium Sulfide-Na2S Chemical Information
Sodium Sulfide – Na2S – Physical Properties
Sodium Sulfide – Na2S – Chemical Properties
Sodium sulfide dissolves in water and forms the ions it needs. The following is the reaction.
Na2S + H2O → 2 Na+ + HS– + OH–
When heated, it quickly oxidized to generate sodium carbonate and sulphur dioxide.
2Na2S + 3O2 + 2CO2 → 2Na2CO3 + 2SO2
Polysulfides are formed when it reacts with sulphur.
2Na2S + S8 → 2Na2S5
When sodium sulfide is dissolved in water, it forms its corresponding ions. The reaction of the same is given below:
Na2S + H2O → 2 Na+ + HS- + OH-
Also, sodium sulfide oxidises quickly by heating. The results will be sodium carbonate and sulfur dioxide.
2Na2S + 3O2 + 2CO2 → 2Na2CO3 + 2SO2
When sodium sulfide goes under oxidation with hydrogen peroxide, it gives sodium sulfate as a result.
Na2S + 4 H2O2 → 4 H2O + Na2SO4
If sodium sulfide is reacted with sulfur, it forms a polysulfide, given as below:
2Na2S + S8 → 2Na2S5
How is Sodium Sulfide Produced?
In industries, Na2S is produced by a carbothermic reduction reaction. In this reduction reaction, carbon is used as a reducing agent.
Similarly, for sodium sulfide, sodium sulfate is reacted by coal.
Na2SO4 + 2 C → Na2S + 2 CO2
In laboratories, the sodium sulfide salt is usually prepared by the reduction method. Sodium sulphur is reacted by anhydride ammonia, or through sodium in dry THF, with the help of naphthalene as a catalyst. The result formed will be sodium naphtha lenoide.
2Na + S → Na2S
Sodium Sulfide (Na2S) has a Variety of Applications
It is employed as an oxygen scavenger and a metal precipitant in water treatment.
Used as a bleaching agent in the textile sector to preserve developer solutions from oxidation in the photographic business.
It's used to make elastomeric synthetic materials, sulphur colours, and other things.
In the crafting process, it's mostly used in the pulp and paper sector. It improves the sulphate cooking process' selectivity and speeds up the delignification process.
Uses of Sodium Sulfide
In the paper and pulp business, it's used in the kraft process.
In water treatment, it's used as an oxygen scavenger.
In the textile sector, it is used as a bleaching agent.
Sodium sulfide is mainly used in the pulp and paper industry for the kraft process. As in the kraft process, wood is converted into wood pulp, sodium hydroxide and sodium sulfide help to dissolve the lignin of wood fibre.
This compound is used in water treatment. In this method, sodium sulfide acts as an oxygen scavenger agent
For chemical photography, sodium sulfide is used as a metal precipitant for toning black and white photographs
In the textile industry, sodium sulfide is used as a bleaching agent, dechlorinating agent and also desulphurising agent.
In the production of rubber chemicals, sulfur dyes and other chemical compounds are used.
Used in various applications like ore flotation, dye-making, oil recovery and detergent.
Safety Measures:
Used as an unhairing agent in the liming process during leather production.
Because sodium sulfide is a strong alkaline, it causes skin burns.
When sodium sulfides combine with acid quickly, it produces poisonous hydrogen sulfide.
Side Effects of Sodium Sulfide
It's normal for the top layer of skin to peel slightly. Irritation, redness, and scaling of the skin are also possible side effects. Stop taking this medication and inform your doctor or pharmacist right away if any of these effects persist or worsen.
Keep in mind that your doctor ordered this medication because he/ she believes the benefit to you outweighs the risk of adverse effects. The majority of people who take this medicine do not have any substantial adverse effects.
Sodium sulfide is strongly alkaline. It can cause significant skin burns. Reacting with acid can form hydrogen sulfide, which is a highly toxic and flammable gas. In reduced ventilation spaces, hydrogen sulfide accumulates at the bottom. To use hydrogen sulfide, one should keep the safety data sheet with them.
Na2S + 2HCl → 2NaCl + H2S(g)
What's the Type of Bonding of Sodium Sulfide?
Sodium sulfide compound is an ionic compound. There are 2 Na atoms per 1 Sulfide atom. It has a central Sulfur atom encircled by 4 Oxygens in covalent bonds. The Sodium atoms and Sulfur or Oxygen atoms in the compound exchange their electrons. Moreover, Sulfur is in group 6, and it requires two more electrons to attain a noble gas state of Argon.
Likewise, the remaining 2 Sodium atoms want to lose 1 electron each to become the noble gas state of Neon. Thus, the 2 Sodium atoms each provide one electron to the Sulfur atom, helping it to be stable in its outer shell.
Since the Sodium atoms give away all its extra electrons to its outermost shell, the two atoms attain the noble gas configuration of Neon and hence become stable.
FAQs on Sodium Sulfide Explained: Structure, Properties & Uses
1. What is sodium sulfide and what is its chemical formula?
Sodium sulfide is an inorganic chemical compound with the formula Na₂S. It is a salt formed from a strong base (sodium hydroxide) and a weak acid (hydrogen sulfide). In its pure, anhydrous form, it is a white crystalline solid. However, it is more commonly available in a hydrated form, such as sodium sulfide nonahydrate (Na₂S·9H₂O), which often has a yellow appearance due to the presence of polysulfides.
2. What are the major industrial applications of sodium sulfide?
Sodium sulfide has several important industrial uses, primarily because of its properties as a strong reducing and sulfidizing agent. Key applications include:
- Pulp and Paper Industry: It is used in the Kraft process to break down lignin in wood pulp.
- Textile Industry: It is used as a bleaching agent and for manufacturing sulfur dyes.
- Water Treatment: It acts as an oxygen scavenger and a metal precipitant to remove heavy metals from wastewater.
- Leather Tanning: It is used in the dehairing process of animal hides.
- Chemical Manufacturing: It serves as a precursor in the production of rubber chemicals, sulfur dyes, and other sulfur compounds.
3. Why does an aqueous solution of sodium sulfide become basic (alkaline)?
An aqueous solution of sodium sulfide is basic due to a process called salt hydrolysis. Sodium sulfide (Na₂S) dissociates in water into sodium ions (Na⁺) and sulfide ions (S²⁻). The sulfide ion is the conjugate base of a weak acid (H₂S). It reacts with water, accepting a proton to form the hydrosulfide ion (HS⁻) and releasing hydroxide ions (OH⁻). This increase in the concentration of OH⁻ ions makes the solution alkaline, raising its pH above 7.
4. Why does sodium sulfide develop a rotten egg smell when exposed to moist air?
Pure, anhydrous sodium sulfide is essentially odourless. The characteristic rotten egg smell is not from the compound itself but from the gas it produces upon reacting with moisture. When sodium sulfide is exposed to moist air, it undergoes hydrolysis, reacting with water (H₂O) to form sodium hydroxide (NaOH) and highly toxic hydrogen sulfide (H₂S) gas. It is this hydrogen sulfide gas that has the strong, unpleasant odour associated with rotten eggs.
5. Is sodium sulfide considered a hazardous substance?
Yes, sodium sulfide is classified as a hazardous and corrosive substance. Direct contact can cause severe burns to the skin and eyes. Ingestion is highly toxic. A significant danger is its reaction with acids, which rapidly releases large amounts of poisonous and flammable hydrogen sulfide gas. Therefore, it must be handled with appropriate personal protective equipment (PPE) in a well-ventilated area, away from acids and oxidizing agents.
6. How does the ionic bonding in sodium sulfide explain its high melting point?
Sodium sulfide has a high melting point (1,176 °C) because it is an ionic compound. It is formed by the transfer of electrons from sodium atoms (a metal) to a sulfur atom (a non-metal), creating positively charged sodium ions (Na⁺) and negatively charged sulfide ions (S²⁻). These oppositely charged ions are held together in a rigid crystal lattice by strong electrostatic forces of attraction. A large amount of thermal energy is required to overcome these strong forces and break down the lattice structure, resulting in a high melting point.
7. Is sodium sulfide an electrolyte?
Yes, sodium sulfide is a strong electrolyte. When dissolved in water, it completely dissociates into its constituent ions: two sodium ions (Na⁺) and one sulfide ion (S²⁻). Because these charged particles are free to move throughout the solution, they can conduct electricity efficiently, which is the defining characteristic of an electrolyte.
8. How is industrial-grade sodium sulfide typically prepared?
On an industrial scale, sodium sulfide is most commonly produced through the carbothermic reduction of sodium sulfate (Na₂SO₄), often using coal as the reducing agent. In this high-temperature process, sodium sulfate is heated with carbon. The carbon reduces the sulfate, producing sodium sulfide and carbon monoxide gas. The simplified chemical equation for this reaction is: Na₂SO₄ + 4C → Na₂S + 4CO.
