Question

2.00g of a certain Compound X, known to be made of carbon, hydrogen and perhaps oxygen, and to have a molecular molar mass of 70g/mol , is burned completely in excess oxygen, and the mass of the products carefully measured: carbon dioxide: 6.29g water: 2.57g

Answer 1

moles of CO2 = (6.29 g) / (44.01 g/mol) = 0.143 mol moles of carbon = 0.143 mol weight of carbon = (0.143 mol) x (12.01 g/mol) = 1.72 g moles of H20 = (2.57 g)/(18.02 g/mol) = 0.143 mol moles of Hydrogen = 2 x 0.143 mol = 0.286 mol weight of Hydrogen = (0.286 mol) (1.01 g/mol) = 0.288 g weight of oxygen = 2.0 g - (1.72 g +0.28 g) =0 g No oxygen in it Simplest mol ration C = (0.143 mol) / (0.143 mol) = 1 H = (0.286 mol) / (0.143 mol) = 2 Empirical formula is: CH2 Empirical mass = 14 g/mol molecular mass = 70 g/mol Molecular formula: C5H10