Units of Measurement

Phytotechnology Laboratories products and the PhytoTech Wiki both utilize the metric system (as applicable) when addressing units of measurement. Listed below are several units of measurement used in the PhytoTech Wiki. This is not intended to serve as a comprehensive list of units of measurement.

Measuring Concentration
A mole is the the base unit of amount of pure substance in the International System of Units that contains the same number of elementary entities as there are atoms in exactly 12 grams of the isotope carbon 12.

The molecular weight is calculated as the sum of the atomic weights of the constituent atoms.

A molecule is the smallest particle of a substance that retains all the properties of the substance and is composed of one or more atoms.

Making Moles Easy to Understand:

Moles can be a very confusing part of chemistry for some people. But in reality moles are very easy. It may help you to think of a mole as a "Scientist's Dozen." When you have a dozen eggs you have 12 eggs. Likewise when you have one mole, you have 6.02 × 1023 molecules. This number of molecules is known as Avogadro's Number or Avogadro's constant.

Where moles become confusing for most people is when using them to determine weight. The number of grams in one mole varies from substance to substance. But think of it like this: one dozen eggs do not weigh the same as one dozen cars. For example: one mole of Oxygen is 15.9994g while one mole of Carbon is 12.0107g. How you determine this weight is incredibly simple, all you need is the periodic table of elements. Each element has a different atomic weight, that weight is the weight in grams of one mole of that element.

You can then extend this concept to determining the weight of one mole of any chemical compound. One mole of a chemical compound is equal to the molecular weight of that compound. You determine the molecular weight of a compound by adding the atomic weight of each element in the compound. Using water as an example: to determine the molecular weight of water, H2O, you add the atomic weight of oxygen (the atomic weight of oxygen is 15.9994 or roughly 16.0) to the atomic weight of each instance of hydrogen (the atomic weight of hydrogen is 1.0079 or roughly 1.0). The weight of one oxygen and two hydrogen is roughly 18.0, the approximate molecular weight of water. So one mole of water is equal to approximately 18.0 grams.

By using moles you can calculate the number of molecules in a sample by weighing it.

Moles in Plant Tissue Culture:

The most common usage of moles in plant tissue culture is in referencing moles per liter (mol/L). Media formulations often require that certain elements be present in specific molar concentrations. For example most media formulations contain at least 25-60mM of inorganic nitrogen. Using moles you can determine then, that most media formualtions contain at least 0.35-0.84g of inorganic nitrogen per liter.