The correct option is A 7
∙ Helium exists as a monoatomic gas (He) whereas nitrogen gas is a diatomic molecule (N2).
∙ Gram molecular mass of a substance is the sum of gram atomic masses of the constituent atoms.
Gram molecular mass of N2 = 2×14 g = 28 g.
Gram atomic mass of He = 4 g
Let us assume that the mass of x moles of helium is equal to the mass of one mole of nitrogen gas.
4x=28⟹x=7
So, 7 moles of helium gas will have a mass equal to that of 1 mole of nitrogen gas.