Make a Short Note on the Physical Properties of Sodium Hydroxide

Have you ever wondered about the physical properties of sodium hydroxide, such as it has a high viscosity, is water-soluble, and hydrates? Sodium hydroxide is a white, basic, water-soluble cation. Sodium hydroxide has a high alkaline pH of ~13. It is a powerful substance that can be used to make soap and shampoo that produces bubbles. The physical properties of sodium hydroxide depend on its molecular weight, the types and proportions of each atom in this molecule, and temperature. The physical properties of sodium hydroxide, the structure of Sodium Hydroxide, along with some basic properties are discussed in this article.

About Sodium Hydroxide

The molecule of Sodium Hydroxide is composed of sodium ions at the centre surrounded by hydroxyl ions with cations and neutral hydrogen atoms on both sides of the sodium ion in a water molecule; therefore will form an ionic bond to liquids and can dissociate in acidic solutions. It is also called soap sodium or salt. It is a chemical compound and also is a solid at room temperature. It is colourless or white when it is pure, but impure sodium hydroxide can be coloured due to either rust from impurities or the presence of other elements.

Sodium hydroxide is a highly caustic and corrosive substance that should never be swallowed and should not get in your eyes.

Sodium hydroxide hydrates into a liquid that has viscosity. The viscosity of sodium hydroxide depends on its purity, temperature, and amount of water available. When the amount of water is less than 1%, it is more viscous. 

Physical Properties of Sodium Hydroxide

• It is water-soluble.

• Liquid Phase: Not soluble in water

• Solid Phase: Soluble in water, soluble in alcohols, soluble in oils and ethers, insoluble in hydrocarbons, does not dissolve in acids.

• Sodium hydroxide has a wide range of aqueous solubility, as it can dissolve easily in both cold and hot water without the evolution of heat.

• Aqueous solutions of sodium hydroxide are alkaline. They are also called caustic soda or lye. On the pH scale, sodium hydroxide is approximately 12 (a pH of 7 is neutral).

• When it reacts with an acid, sodium hydroxide releases hydrogen gas (H2).

• The molecule of sodium hydroxide is composed of sodium ions at the centre surrounded by hydroxyl ions with cations and neutral hydrogen atoms on both sides of the sodium ion in a water molecule; it, therefore, will form an ionic bond to liquids and can dissociate in acidic solutions. It is also called soap sodium or salt. It is a physical, chemical, and solid at room temperature.

• Shape: Cone, Prism Needle, Cubic Pyramid Linear Octahedron.

• Sodium hydroxide hydrates into a white solid called sodium carbonate, that is also derived from sodium hydroxide at higher temperatures.

• It also hydrates into a grey powder called potassium carbonate, which is made out of potassium hydroxide at lower temperatures.

• It hydrates into a white powder called sodium sulphate.

• Sodium hydroxide hydrates into an unusual chemical compound called dibasic sodium sulphate. 

• Dibasic sodium sulphate is used as an additive for soap making and for the cleaning of boats, tools, and machinery. 

• Another interesting thing about this compound is that it has the same compounds in bulk. Still, the compounds are agglomerated, and each sodium ion combines with two chlorine ions to form a divalent oxide (sodium chloride).

Chemical Properties of Sodium Hydroxide

• Sodium hydroxide, also known as lye, is a white solid and highly corrosive, alkaline substance that consists of sodium cations and hydroxide ions.
• Sodium hydroxide dissociates into sodium cation (Na+) and hydroxyl anion (OH–) particles in water.
• Sodium hydroxide is a base and, as such, can react with acid to produce water and release hydrogen gas.
• Density: 1.429 g/cm3
• Vapour Pressure: 0.85mmHg at 66℃
• Dissociation Constant, “pH” (1 Molar): 11.07 at 25 ℃.
• The vapour pressure of sodium hydroxide is low (0.85 mmHg at 66℃) because it’s very soluble in water and thus when exposed to the air, transfers the NaOH molecules to water via the ion product or reaction:

NaOH  → Na+ + OH–

Uses of Sodium Hydroxide

Sodium hydroxide is used in many industries, such as:

• Paper: Sodium hydroxide is used in the “cooking” of wood pulp to make paper.
• Soap and Detergents: When sodium hydroxide combines with fats, it forms the compound of soap—natural or synthetic.
• Textiles: It is used in bleaching fibres.
• Chemical Industry: Sodium hydroxide is used as a strong base to generate acidic solutions and neutralise bases.
• Food: It is used in the manufacture of food products, such as cheese and butter.
• Cosmetics: Sodium hydroxide is also used in making soap and some cosmetics products. It is used in some pharmaceutical and organic industries to make active pharmaceutical ingredients (APIs).

Conclusion

The physical properties of sodium hydroxide are discussed in this article. Sodium hydroxide changes slightly with temperature; as the temperature rises, it gets thicker at first and then becomes thinner again as the temperature increases further. It hydrates into a high viscosity solution, which depends on the purity of sodium hydroxide, amount of water, and temperature. It also hydrates into a white solid called sodium carbonate, which is also derived from sodium hydroxide at higher temperatures. Also, it can be used as an additive for soap making and the cleaning of boats, tools, and machinery.