# Mole Concept and Molar mass

Mole:

• Unit of amount of substance.
• One mole amount of substance that contains as many particles or entities  as there are atoms in exactly 12 g of the 12C isotope.

Molar mass:

• Mass of one mole of a substance in gram
• Molar mass in gram in numerically equal to atomic/molecular/formula mass in amu or u.

Mole concept

• One mole of a substance (atoms, molecules, ions, or particles) is that quantity in number having a mass equal to its atomic or molecular mass in grams.
• The Avogadro constant is the number of particles (usually atoms or molecules) in one mole of a given substance.
• Its value is equal to 6.022 ×1023 mol−1
• The constant was named after the Italian scientist Amedeo Avogadro.
• Avogadro number is denoted by N0.
• One-mole molecule of any substance contains 6.022 x 1023 molecules.

Percentage composition:

Mass percentage of an element in a compound =  (Mass of that element in the compound / Molecular mass of the compound)×100

Percentage yield:

• It is the ratio of actual yield of the reaction to the theoretical yield multiplied by 100.
• % yield = (Actual yield /Theoretical yield) ×100

Empirical and Molecular formula

• An empirical formula represents the simplest whole number ratio of various atoms present in a compound.
• The molecular formula shows the exact number of different types of atoms present in a molecule of a compound.

For example-

Hydrogen peroxide

• Molecular formula – H2O2
• Empirical formula – HO

For example –

Empirical formula of iron oxide , has 69.9% of iron and 30.1 % of oxygen by mass.

Empirical formula = Fe2O3