Sodium Hydroxide (NaOH): Formula, Properties, Preparation, Uses

An inorganic compound with the chemical formula NaOH is sodium hydroxide, also known as lye and caustic soda. The substance in question is a solid ionic compound characterized by its white color. It comprises sodium cations (Na+) and hydroxide anions (OH). Sodium hydroxide is classified as a solid ionic compound.

Sodium hydroxide is generated simultaneously during the production of Chlorine. In its unadulterated state, the substance exhibits a crystalline structure and lacks any discernible coloration. The compound in question shows a high degree of solubility in water and is composed of sodium cations and hydroxide anions. Sodium hydroxide (NaOH) exhibits hygroscopic properties, leading to its ability to readily absorb moisture from the surrounding atmosphere. The substance shows a high degree of corrosiveness, thereby posing the potential to induce significant skin burns and irritation to the ocular and other anatomical regions.

The production of a significant amount of heat is observed, thus necessitating the addition of the compound to the water rather than the reverse process. This particular inorganic compound is employed as a buffering agent within the realm of cosmetics. Furthermore, it has the capability to regulate pH levels. The pH value of sodium hydroxide is 13. Sodium hydroxide is occasionally referred to as caustic soda. It is a commonly utilized component in cleaning agents and cleansing agents. At room temperature, sodium hydroxide is a colorless and odorless compound. The liquid form of sodium hydroxide is devoid of color and scent. The substance exhibits a high degree of reactivity toward both strong acids and water.

Physical Properties of Sodium Hydroxide

  • Sodium hydroxide is an ionic crystal composed of Na+ cations and OH anions. It is characterized by its colorless appearance, lack of odor, and high deliquescence.
  • The substance exhibits a high degree of solubility in aqueous solutions, and its dissolution is accompanied by the release of thermal energy. At a temperature of 20 °C, the solubility of sodium hydroxide (NaOH) in water is 109 grams per 100 grams of water. Additionally, the heat of solution for this process is -44.5 kJ mol-1 (kilojoules per mole). Additionally, it exhibits solubility in methanol and ethanol, with solubilities of 23.8 g/100g and 13.9 g/100g at a temperature of 20°C, respectively.
  • Aqueous solutions containing sodium hydroxide exhibit a characteristic soapy consistency; however, it is important to note that these solutions possess a significant degree of corrosiveness toward the skin, eyes, and mucous membranes. In addition, it has the ability to cause corrosion on surfaces composed of metal and glass. The side effects of this substance include transient alopecia and an allergic response. Therefore, it is imperative that the matter be approached with care.
Sodium HydroxideNaOH
Molecular weight / Molar mass39.997 g/mol
Density2.13 g/cm³
Boiling Point1388 °C
Melting Point318 °C

Chemical Properties of Sodium Hydroxide

(1) Precipitation Reactions

Numerous salt solutions undergo precipitation when treated with an aqueous solution of sodium hydroxide.

(i) The Reaction of Sodium Hydroxide With Copper (II) Sulfate Solution

Upon the addition of a sodium hydroxide solution, a chemical reaction follows, resulting in the formation of a noticeable light green precipitate. The resulting precipitate is comprised of cupric hydroxide, a compound consisting of copper and hydroxide ions. After a series of changes in temperature, the green precipitate we just talked about breaks down into a dark brown precipitate made of cupric oxide.

CuSO4 + 2 NaOH → Cu(OH)2↓ + Na2SO4


Cu(OH)2 [when heated Δ]  → CuO↓ + H2O


(ii) The Reaction of Sodium Hydroxide With Ferrous and Ferric salt

The aqueous solution of sodium hydroxide engages in a chemical reaction with solutions containing ferrous and ferric salts, leading to the creation of a visually cloudy green precipitate comprised of ferrous hydroxide, as well as a reddish-brown precipitate comprised of ferric hydroxide, respectively.

FeSO4 + 2 NaOH → Fe(OH)2↓ + Na2SO4

Dirty Green

Fe2(SO4)3 + 6 NaOH → 2 Fe(OH)3↓ + 3 Na2SO4


(iii) The Reaction of Sodium Hydroxide With Chromic Salts

The reaction between a solution of sodium hydroxide and a solution of chromic salt results in the formation of a green precipitate composed of chromic hydroxide.

Cr2(SO4)3 + 6 NaOH → 2 Cr(OH)3↓ + 3 Na2SO4


When the green precipitate is subjected to an excess of sodium hydroxide in the presence of peroxide, it results in the formation of a yellow-colored solution of sodium chromate.

2 Cr(OH)3 + 4 NaOH + 3 H2O2 → 2 Na2CrO4↓ + H2O

Green ppt Yellow solution

(iv) The Reaction of Sodium Hydroxide With Aluminium And Zinc Salts

Gelatinous white precipitates consisting of aluminum hydroxide and zinc hydroxide are formed through the addition of a restricted amount of sodium hydroxide to the aqueous solution containing their respective salts.

Al2(SO4)3 + 6 NaOH → 2 Al(OH)3↓ + 3 Na2SO4

ZnSO4 + 2 NaOH → Zn(OH)2↓ + Na2SO4


Upon the addition of an excessive quantity of sodium hydroxide, the gelatinous white precipitate experiences dissolution, leading to the creation of a solution devoid of color. This solution contains meta aluminate and zincate.

Al(OH)3 + NaOH → NaAlO2 + 2 H2O

(sodium meta aluminate)

Zn(OH)2 + 2 NaOH → Na2ZnO2 + 2 H2O

(sodium zincate)

(v) The Reaction of Sodium Hydroxide With Mercuric Chloride (Corrosive Sublimate)

The chemical interaction involving a solution of sodium hydroxide and a solution of mercuric chloride leads to the production of a yellow solid precipitate consisting of mercuric oxide.

HgCl2 + 2 NAOH → HgO↓ + 2 NaCl + 2 H2O

(2) Addition Reaction With Carbon monoxide (CO)

The generation of sodium formate occurs when concentrated sodium hydroxide is subjected to heating with carbon monoxide gas under a pressure of 50 atm pressure and at a temperature of 160°C. (sodium formate)


(when heated to 160°C at 50 atm)

(3) Basic Nature

A strong base, known as an alkali, exhibits the ability to induce a color change in various indicators. Specifically, it changes red litmus paper to blue, phenolphthalein to pink, and methyl orange to yellow. Several fundamental reactions can be identified, including the following:

(i) The Reaction of NaOH With Inorganic And Organic Acids

2 NaOH + H2SO4 → Na2SO4 + 2 H2O


(Acetic acid) (sodium acetate)

(ii) The Reaction of NaOH With Acidic Oxides

2 NaOH + CO2 → Na2CO3 + H2O

2 NaOH + SO2 → Na2SO3 + H2O

6 NaOH + P2O5 → 2 Na3PO4 + 3 H2O

(iii) The Reaction of NaOH With Ammonium Salt

When a solution made up of sodium hydroxide and an ammonium salt is heated the process results in the liberation of Ammonia gas.

NaOH + NH4Cl → NaCl + NH3↑ + H2O

(when heated Δ)

(iv) The Reaction of NaOH With Amphoteric Elements

When heated with sodium hydroxide solution, amphoteric elements such as aluminum (Al), zinc (Zn), tin (Sn), and silicon (Si) undergo a reaction that results in the production of hydrogen gas.

2 Al + 2 NaOH + 2 H2O → 2 NaAlO2 + 3 H2

(sodium meta aluminate)

Zn + 2 NaOH Na2ZnO2 + H2

(sodium zincate)

Si + 2 NaOH + H2O → Na2SiO3 + 2 H2

(sodium silicate)

Sn + 2 NaOH + H2O → Na2SnO3 + 2 H2

(sodium stannate)

Preparation of Sodium Hydroxide

Sodium hydroxide, chemically represented as NaOH, is widely recognized as a highly potent base. Sodium hydroxide is widely recognized as a crucial alkali hydroxide that finds extensive application in laboratory and commercial settings. Historically, sodium hydroxide has been produced in significant quantities using easily accessible raw materials, making it a valuable component in various industrial applications.

The primary method of production involves the electrolysis of a brine solution within either a diaphragm or a Mercury cell. Nevertheless, there exist several additional significant processes by which sodium hydroxide (NaOH) is generated, alongside the production of other substances such as chlorine gas (Cl2) and sodium carbonate (Na2CO3). Different methods of producing NaOH are:

(a) Leblanc Process

The main product of the reaction is the formation of chlorine gas, with the concurrent production of NaOH as a secondary byproduct. The general equation representing the Leblanc process is as follows:

4 HCl + Mna2 → 2 Cl2 + Mn2+ + 2 H2O

In this context, manganese dioxide (MnO2) functions as an oxidizing agent, facilitating the oxidation of hydrochloric acid (HCl) to chlorine gas (Cl2). During earlier times, the process of preparing hydrochloric acid (HCl) was challenging. It is derived from sodium chloride through a reaction with a potent acid.

NaCl + H2SO4 → NaHSO4 + HCl

(conc. sulfuric acid)

NaHSO4 + NaCl → Na2SO4 + HCl

Subsequently, the hydrogen chloride (HCl) that is generated undergoes oxidation.

HCl + MnO2 → Cl2 + Mne+

The byproduct Na2SO4 is utilized in the production of various chemicals, including glass, Na2CO3, and NaOH, through the following processes.

Na2SO4 + C + CaCO3 → Na3CO3 + CaSO4

Na2CO3 + Ca(OH)2 → 2 NaOH + CaCO3

The initial components utilized in this experiment consist of sulfuric acid (H2SO4), sodium chloride (NaCl), calcium carbonate (CaCO3), and carbon (C). The primary products of the reaction are sodium hydroxide (NaOH) and chlorine gas (Cl2). The conversion of CaCO3 to Ca(OH)2 occurs in the following manner:

CaCO3 → CaO → Ca(OH)2

(when heated Δ) (when reacted with H2O)

(b) Weldon’s Process

The Weldon process exhibits similarities to the Leblanc process, differing only in the treatment of Mn2+ (MnCl2) where it is reused in the Weldon process, whereas it is disposed of in the Leblanc process. Therefore, one could contend that Weldon’s process presents itself as a comparatively more economical alternative to the Leblanc process.

(c) Deacon Process

In a manner similar to the aforementioned procedure, hydrogen chloride (HCl) undergoes oxidation. In this context, the air serves as the oxidizing agent for the reaction involving hydrogen chloride (HCl), facilitated by the presence of a catalyst, calcium chloride (CaCl2).

(d) Electrolytic Process 

The production of sodium hydroxide (NaOH) and chlorine gas (Cl2) is achieved through the process of electrolysis applied to a solution of brine, which consists of sodium chloride (NaCl). The electrolytic cell is composed of two electrodes, namely the cathode and anode, which are made of graphite rods. The electrolyte used in this cell is a solution of sodium chloride (NaCl).

Applications of Sodium Hydroxide

Sodium hydroxide occupies a significant role as a widely employed chemical compound in diverse industrial domains. This particular substance is commonly known by the name caustic soda or lye. The alkaline form of sodium oxide is commonly known as alkaline sodium oxide. This section aims to examine the diverse range of usages of sodium hydroxide in different fields.

Used In Industries

Sodium hydroxide is extensively utilized across multiple industries for a variety of purposes. These industries include the production of rayon, particularly cellulose acetate, as well as the manufacturing of epoxy resins, paints, dyes, explosives, soaps and detergents, and papers. This particular substance is utilized in the textile industry for the treatment of cotton fabrics, as well as in the extraction process of aluminum ore. Moreover, this particular substance is widely utilized in diverse sectors, including the glass and ceramic industries, as well as petroleum refineries.

Used In Disinfectant Products

  • Sodium hydroxide (NaOH) is a prominent component utilized in the process of cleaning drains and ovens. Whenever pipes or channels become obstructed due to the accumulation of solidified grease and fats, they can be effectively transformed into soluble soap by treating them with sodium hydroxide. As a result, the blockage can be easily cleared, enabling the maintenance of drain ovens.
  • Sodium hydroxide (NaOH) exhibits notable efficacy in the eradication of microorganisms. At the micro-scale, it effectively eradicates proteins, and nucleic acids, and incapacitates a wide range of viruses upon contact. Furthermore, it possesses the capability to eradicate yeast and fungi. Consequently, sodium hydroxide is employed as a disinfectant in various commercial brands such as Harpic, Lizol, Colin, and others.

Used In Cosmetics

Sodium hydroxide finds application in the field of cosmetics as well. Beauty products, including hair spray, fragrances, foot powder, hair dye, and shampoos, often contain a low concentration of sodium hydroxide. Hair products are designed to create a protective barrier that maintains an acidic environment for the skin, hair, and scalp.

Used In Medicines And Pharmaceutical Products

Sodium hydroxide plays a significant role in the manufacturing of diverse medicines and pharmaceuticals, including cholesterol-reducing products, aspirin, and anticoagulants for blood clot prevention, among others.

Health Effects of Sodium Hydroxide

When managing sodium hydroxide for practical purposes, particularly in large quantities, it is imperative to exercise caution during storage due to the chemical’s potential to cause burns. Sodium hydroxide has the capacity to be contained within bottles for the purpose of small-scale laboratory applications.

  • Sodium hydroxide is a potent and highly corrosive alkali that has the ability to degrade organic tissues.
  • Direct exposure to sodium hydroxide (NaOH) can potentially result in irreversible visual impairment due to its corrosive properties.
  • Exposure to sodium hydroxide (NaOH) through direct contact with the skin can result in the occurrence of significant chemical burns.



About Author

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Jyoti Bashyal

Jyoti Bashyal, a graduate of the Central Department of Chemistry, is an avid explorer of the molecular realm. Fueled by her fascination with chemical reactions and natural compounds, she navigates her field's complexities with precision and passion. Outside the lab, Jyoti is dedicated to making science accessible to all. She aspires to deepen audiences' understanding of the wonders of various scientific subjects and their impact on the world by sharing them with a wide range of readers through her writing.

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