Answer : The correct option is, 3.75 mole [tex]N_2[/tex]
Explanation : Given,
Moles of [tex]NaN_3[/tex] = 2.5 mol
The balanced chemical equation is:
[tex]2Na+3N_2\rightarrow 2NaN_3[/tex]
From the balanced reaction we conclude that
As, 2 moles of [tex]NaN_3[/tex] produce from 3 moles of [tex]N_2[/tex]
So, 2.5 moles of [tex]NaN_3[/tex] produce from [tex]\frac{3}{2}\times 2.5=3.75[/tex] moles of [tex]N_2[/tex]
Therefore, the moles of [tex]N_2[/tex] initially present was, 3.75 moles.