Question

Explain or define the following terms:

a) molar absorptivity

b) path length

c) ligand

Answer 1

Molar absorptivity : Molar absorptivity also known as the molar attenuation coefficient is a measurement of how strongly a chemical species attenuates light at a given wavelength. It is an intrinsic property of the species. The SI unit of molar attenuation coefficient is the square metre per mole (m²/mol), but in practice, it is usually taken as the M^?1?cm^?1 or the L?mol^?1?cm^?1.

Path length : The path length is defined as the distance that light (UV/VIS) travels through a sample in an analytical cell. Typically, a sample cell is made of quartz, glass, or a plastic rhombic cuvette with a volume typically ranging from 0.1 mL to 10 mL or larger used in a spectrophotometer. For the purposes of spectrophotometry (i.e. when making calculations using the Beer-Lambert law) the path length is measured in centimeters (rather than in meters).

Ligand : A ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from covalent to ionic and the metal-ligand bond order can range from one to three.