Determine the molar masses of hydrogen and helium.

Molar mass is the mass of one mole of a substance. To find the molar mass of a substance, it is necessary to add up the molar masses of the atoms included in it. Hydrogen contains one hydrogen atom; its atomic mass is known from the periodic table of elements of Mendeleev, equal to about 1 g / mol. Accordingly, the molar mass of the substance hydrogen is 1 g / mol. A helium molecule contains 4 hydrogen atoms – the molar mass of helium is M = 4 * 1 = 4 g / mol.