Chemical Formula: NaOH
Synonyms: caustic soda, lye (sodium hydroxide solid) or sodium hydrate.
Table 1.0: Physical Properties of Sodium Hydroxide.
Molecular Weight 39.997g/mol
Appearance (solid) White Crystalline Substance
Transparent Only in liquid form
Boiling Point 1390°C
Melting Point 318°C
Freezing Point 14°C
Vapour Pressure (0.2 kPa, 20°C) 1.5mmHg
Specific Gravity (20°C) 1.52g/ml
Table 1.1: Chemical Properties of Sodium Hydroxide.
Chemical Formula NaOH
Acidity Very Low (13-14 pH)
Basic Type Caustic Metallic Base
Solubility (20°C) 1110g/L
Soluble (in) Water, acids, alcohol and
The hydroxide ion is a component of the sodium hydroxide, this anion makes this compound a very
strong base which react with any acid which will neutralise each other, according to Bronsted-
Lowry’s theory. In general, neutralisation reactions can be represented as follows in an ionic
OH−(aq) + H+(aq) → H2O(l)
Sodium hydroxide reacting with an acid will generally result in a neutralisation process, which will
produce water and a corresponding salt depending upon the acid reacted with. For instance, sodium
hydroxide reacts with hydrochloride acid:
NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
The Structure of Sodium Hydroxide
Sodium Hydroxide is composed of a sodium ion (Na+) and a hydroxide ion (OH-). It is an ionically
bonded compound, which comprises of a metal and non-metal. The Sodium metal loses an electron
and forms Na+ ion and requires energy to make remove one electron since sodium metal is its most
The hydroxide ion (non-metal) is from a water molecule and it requires a lot of energy to split into a
hydrogen ion and a hydroxide ion since hydroxide ion is readily reactive.
Sodium Hydroxide: Since both ions have a 1:1 ratio of the same degree of charges, this will form a
neutral compound. Although, the hydroxide ion is larger than the sodium ion making it more
negative than positive.
General Form of Sodium Hydroxide Molecule:
Na – OH