Question

“ The number of atoms in a certain volume of hydrogen is twice the number of atoms in the same volume of helium at same temperature and pressure.” Why ?

Answer 1

• According to Avogadro's Law , equal volumes of all the gases contain same number of molecules under same conditions of temperature and pressure.
• Since Hydrogen gas ${\mathrm{H}}_2$ is a diatomic molecule, it contains two atoms of hydrogen in one molecule.
• But Helium gas $\mathrm{He}$ is monoatomic, so there is one atom of Helium .
• Since ${\mathrm{H}}_2$ gas and $\mathrm{He}$ gas have different atomicity where atomicity of hydrogen gas is twice the atomicity of helium gas,The number of atoms in a certain volume of hydrogen is twice the number of atoms in the same volume of helium at same temperature and pressure.”