Class - 11th || Chemistry || Chapter-1 || Basic concept of Chemistry || By Ramesh Sir || part 3

Molar Mass

The molar mass of a substance is defined as the total mass of one mole of the substance. It is often represented in terms of ‘grams per mole’ (g/mol). However, the SI unit of this quantity is kg/mol. Molar mass can be represented by the following formula:
Molar mass of a Substance = (Mass of the Substance in grams)/(Number of Moles)
For example, the molar mass of water is approximately 18.015 g/mol, which is the mass of NA number of water molecules.

Gram Atomic Mass and Gram Molecular Mass

The gram atomic mass of an element is the mass of one mole of that element. Similarly, the gram molecular mass of a compound refers to the mass of a single mole of the compound. Therefore, the gram atomic mass of hydrogen is approximately 1.007g and the gram molecular mass of water is approximately 18.015g.

Related Formulae

The number of moles in a given sample of an element/compound can be calculated by dividing the total mass of the sample by the molar mass of the element/compound, as described by the following formula.
Number of Moles = (Mass of the Sample)/(Molar Mass)
The total number of atoms/molecules in a sample can be calculated by multiplying the number of moles with the Avogadro constant. This formula can be written as:
Number of Atoms or Molecules = (Number of Moles)*(6.022*1023)
The relationship between the atomic mass unit (amu) and the gram is given by:
1 amu = (1gram)/(6.022*1023) = 1.66*10-24 grams
Therefore, the mass of one mole of an element will be equal to its atomic mass in grams.
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