If average molecular wt. of air is 29, then assuming N₂ and O₂ gases are there which options are correct regarding composition of air:
(i) 75% by mass of N₂
(ii) 75% by moles N₂
(iii) 72.47% by mass of N₂

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only (i) is correct

only (ii) is correct

both (ii) and (iii) are correct

both (i) and (ii) are correct

answer is C.

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Detailed Solution

Let total mass be

$\begin{array}{l} M_{Avg} = \frac{Total mass}{Total moles} \\ 29 = \frac{100}{\frac{x}{23} + \frac{(100 - x)}{32}} \Rightarrow x = 72 .41 % \end{array}$

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