What is the molecular formula for the compound that is made up of 30.45 g N and 69.55 g O, and has a formula mass of 92.02 amu?

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Answer 1 · 2018-04-14T10:43:58

$"N"_2"O"_4$

Moles of nitrogen

$"n"_"N" = "30.45 g"/"14 g/mol" = "2.175 mol"$

Moles of oxygen

$"n"_"O" = "69.55 g"/"16 g/mol" = "4.347 mol"$

Ratio of moles of nitrogen and oxygen

$"n"_"N"/"n"_"O" = "2.175 mol"/"4.347 mol" ≈ 1/2$

∴ Emperical formula $"= NO"_2$

$"Molecular formula mass"/"Emperical formula mass" = "92.02 amu"/"46.0 amu" ≈ 2$

∴ Molecular formula $= 2 × "NO"_2 = color(Green)("N"_2"O"_4)$