A compound is found to be 30.45% N and 69.55% O by mass.If 1.63 g of this compound occupy 389 mL at 0.00°C and 775 mm Hg,what is the molecular formula of the compound?

Question

Quizplus · Accepted Answer

1. Find the empirical formula of the compound: Mass of N = 0.3045 g Mass of O = 0.6955 g Convert mass to moles: Moles of N = 0.3045 g / 14.01 g/mol = 0.02177 mol Moles of O = 0.6955 g / 16.00 g/mol = 0.04347 mol Divide by the smallest number of moles (0.02177) to get the empirical formula: N:O = 1:2 Empirical formula = NO2 2. Find the molecular formula of the compound: First, find the molar mass of the empirical formula: Mass of NO2 = (14.01 g/mol x 1) + (16.00 g/mol x 2) = 46.01 g/mol Next, find the number of empirical formula units in the molecular formula: Molecular weight / empirical weight = n n = 1.63 g / (46.01 g/mol) = 0.0354 mol Divide each subscript in the empirical formula by the smallest subscript (1) to get the ratio of subscripts: N1O2 Multiply each subscript by n to get the molecular formula: N1 x 0.0354O2 x 0.0354 = N1O1.9948 ≈ N1O2 Therefore, the molecular formula is N₂O₄.

A Compound Is Found to Be 30