Question

A gaseous compound of nitrogen and hydrogen contains 12.5% hydrogen by mass. Find the molecular formula of the compound if it’s relative molecular mass is 37. [N =14, H = 1].

August 5, 2024

Answer

Element	% composition	At. wt.	Relative no. of atoms	Simplest ratio
Nitrogen	100 – 12.5 = 87.5	14	87.5/14 = 6.25	6.25/6.25 = 1
Hydrogen	12.5	1	12.5/1 = 12.5	12.5/6.25 = 1

Simplest ratio of whole numbers N : H = 1 : 2

Hence, empirical formula is NH₂

Empirical formula weight = 14 + 2(1) = 16

Relative molecular mass = 37

n = $Molecular\ weight\over Empirical\ formula\ weight$

= $37\over 16$

=2.31 = 2

∴ Molecular formula = [NH₂]₂ = N₂H₄

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