What is the number of moles of ‘He’ in 104 g of helium gas ?

To determine the number of moles of helium (He) in a given mass, the standard formula used is the given mass divided by the molar mass of the element. The atomic mass of helium is approximately 4 atomic mass units (u), which corresponds to a molar mass of 4 g/mol. Given that the mass of the helium gas is 104 g, the calculation is performed by dividing 104 g by the molar mass of 4 g/mol. This calculation (104 / 4) results in exactly 26 moles. Helium is a noble gas with an atomic number of 2, and its molar mass is consistently defined as approximately 4.003 g/mol in chemical standards [1]. Therefore, 104 g of helium contains 26 moles of helium atoms.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > 3.3 HOW DO METALS AND NON-METALS REA ALS REACT? > p. 47