Question

How many moles of helium will have a mass equal to the mass of 1 mole of nitrogen gas?

• A. 7
• B. 6
• C. 4
• D. 8

Answer 1

The correct option is A 7

$\bullet$ Helium exists as a monoatomic gas (He) whereas nitrogen gas is a diatomic molecule ($N_2$).

$\bullet$ Gram molecular mass of a substance is the sum of gram atomic masses of the constituent atoms.

Gram molecular mass of $N_2$ = $2\times 14$ 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.