The term CHEM. UNIT refers to two chemical units, a Mole (MOL) and an ESTER (ESTER). A Mole is a unit of measurement in chemistry that is used to measure the amount of a substance. It is equal to 6.022 x 10^23 particles of the substance. An ESTER is a type of organic compound that is formed when an acid reacts with an alcohol. It is composed of a carbonyl group bonded to an oxygen atom and two hydrocarbon groups.