Introduction
Every substance that is stated in the periodic table exhibits a specific molar mass. It is different for all elements and is used in the identification of an element or a compound. Molar mass is the weight of one mole of an element and as we know that one mole of every element contains a specific number of atoms of that element. Hence, we can say that the molar mass of each element is also specific and is stated in the literature. A molar mass calculator is used to calculate the molar mass of a given element.
Importance of Molar mass
When a new element or a compound is discovered then first of all its physical and chemical properties are studied. Then comes the structure elucidation of the element where its empirical and molecular formula is predicted.
The structure of the element / compound is designed using all this data. Molar mass plays an important role in the structure elucidation step. In the case of a new compound, it is first converted into fragments and then each fragment is studied separately. Molar mass is equal to the atomic mass of an element and is expressed in grams per mole (g/mol). For example, the atomic mass of fluorine is 19 so the molar mass of fluorine is 19 g/mol.
Calculation of Molar mass
Molar mass is the mass per mole of a substance and is written as “M”. In the case of elements, it is given in the literature while in the case of elements and compounds, you can calculate it using the simple fragments method. But if you are given a certain number of grams of a substance and asked to find its molar mass then there is a formula to calculate it (it would always be equal to the atomic mass of that substance).
Molar mass = mass / number of moles of a substance
The molar mass of a molecule with the same atoms = no. of atoms x molar mass of the atom
M of a compound AB = (no. of atoms of A x M of A) + (no. of atoms of B x M of B)
It is easier to use a molar mass calculator to avoid this hassle. Simply enter the molecular formula or the name of the substance and press the “calculate” button. It would tell you the molar mass of the given substance. following is the example to prove that molar mass is always equal to the atomic mass of a substance.
Example # 1
Calculate the molar mass of 30g sodium metal.
\
Number of moles present in 30 grams of sodium = mass/molar mass (present in literature)
Moles of sodium = 30 / 23
Moles of sodium = 1.3 mol
Molar mass = mass / moles
Molar mass = 30 / 1.3
Molar mass = 23 g/mol
Hence, the molar mass is always equal to the atomic mass of a substance. whatever the data is given to you, the answer would always be equal to the atomic mass (given in literature) of the substance.
Example # 2
Calculate the molar mass of O3.
Molar mass = no. of atoms x molar mass of an atom
Molar mass = 3 x 16
Molar mass = 48g/mol
Answer; the molar mass of an ozone molecule is 48 g/mol.
