What is meant by molar mass?

Molar mass, also known as molecular weight, is a fundamental concept in chemistry that represents the mass of a substance (typically a molecule or an atom) in atomic mass units (amu) or grams per mole (g/mol). It is a critical property because it allows chemists to relate the mass of a substance to the amount of that substance in a given sample, facilitating various chemical calculations.

Here are some key points about molar mass:

Definition: Molar mass is the mass of one mole of a substance. One mole is defined as the amount of a substance that contains the same number of entities (atoms, molecules, ions, etc.) as there are in exactly 12 grams of carbon-12. This number is approximately 6.022 x 10^23, and it's known as Avogadro's number.

Units: Molar mass is expressed in atomic mass units (amu) or grams per mole (g/mol). In the context of chemical calculations, g/mol is more commonly used, as it directly relates the mass of a substance to the number of moles.

Calculation: To calculate the molar mass of a compound, you sum up the atomic masses of all the atoms in the molecule, taking into account the subscripts that indicate how many of each type of atom are present. For example, the molar mass of water (H2O) is calculated as follows:

Molar mass of H2O = (2 × Molar mass of hydrogen) + (1 × Molar mass of oxygen)

Periodic Table: The molar mass of individual elements can be found on the periodic table. It is given in atomic mass units (amu), and you can use these values to calculate the molar mass of compounds.

Importance: Molar mass is essential for various chemical calculations, such as determining the amount of a substance in moles when you know its mass, calculating the mass of a sample given the number of moles, or balancing chemical equations.

In summary, molar mass is a measure of the mass of a substance on a per-mole basis, and it plays a crucial role in stoichiometry and other chemical calculations.