1. By Alan Joye
Sodium Hydroxide
Chemical Formula: NaOH
Synonyms: caustic soda, lye (sodium hydroxide solid) or sodium hydrate.
Physical Properties
Table 1.0: Physical Properties of Sodium Hydroxide.
Property Information
Molecular Weight 39.997g/mol
Appearance (solid) White Crystalline Substance
Transparent Only in liquid form
Odour None
Density 2.13g/cm³
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
Flammable No
Chemical Properties
Table 1.1: Chemical Properties of Sodium Hydroxide.
Property Information
Chemical Formula NaOH
Acidity Very Low (13-14 pH)
Basic Type Caustic Metallic Base
Corrosive High
Reactivity Medium
Hygroscopic Yes
Solubility (20°C) 1110g/L

2. By Alan Joye
Soluble (in) Water, acids, alcohol and
other materials
Neutralisation Reaction
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
equation:
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)
Sodium Hydroxide reaction with acidic oxides
This is another type of reaction that is vital to illustrate in terms for sodium hydroxide due to this
reaction harm gases such as carbon dioxide and sulfur dioxide (production of burning coal) to be
‘scrubbed’ and absorbed, reducing the amount exposed into the atmosphere.
2NaOH(aq) + CO2(g) → Na2CO3(s) + H2O(l)
As you can see, in the above reaction, sodium hydroxide reacts with carbon dioxide gas (harmful gas
to atmosphere) produces sodium carbonate and water. Sodium carbonate (washing soda) is a very
safe compound, which is used in detergents to remove oil, grease and alcohol stains. Basically
reducing a harmful gas into a non-harmful compound.
Saponification Reaction with Sodium Hydroxide
Saponification is a chemical process that results in the production of soap from fatty acids such as
Stearic acid (C17H35COOH)1 and a base like sodium hydroxide (NaOH):
C17H35COOH(s) + NaOH(aq) → C17H35COONa(aq) + H2O(l)
1
A saturated fatty acid.

3. By Alan Joye
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
stable state.
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

4. By Alan Joye
Bibliography
DOW Caustic Soda: "Physical Properties" 1995, viewed 21/9/10, ‹http://www.dow.com/causticsoda/
phys/index.htm›.
Green Planet Solar Energy: "The Structure of Sodium Hydroxide" 2010, viewed 21/9/10,
‹http://www.green-planet-solar-energy.com/sodium-hydroxide.html›.
Sodium Hydroxide 2008, viewed 21/9/10, ‹http://webbook.nist.gov/cgi/cbook.cgi?
ID=C1310732&Units=SI&Mask=1EFF&Type=JANAFL&Table=on#JANAFL›.
Wikipedia: "Sodium Hydroxide" 2010, viewed 21/9/10,
‹http://en.wikipedia.org/wiki/Sodium_hydroxide›.