If average molecular Wt. of air 29, then assuming N2 and O2 gases are there which options are correct regarding composition of air:

Question

If average molecular weight of air 29, then assuming N₂ and O₂ gasses are there which options are correct regarding composition of air: 

(1) 75% by mass of N₂   

(2) 75% by moles N₂ 

(3) 72.41% by mass of N₂ 

(a) Only (1) correct 

(b) Only (2) is correct 

(c) both (2) and (3) are correct 

(d) both (1) and (2) are correct 

Comments

Can you please explain me ? Why option (c) is not the ans

Answer 1

Correct option : (1) 75% by mass of N₂ 

Explanation :

The average atomic mass of air 

The average atomic mass of air