Question

A 0. 1014 g sample of a purified cho compound was burned in a combustion apparatus and produced 0. 1486 g co2 and 0. 0609 g of h2o. What is the empirical formula of this cho compound? enter as c#h#o#, e. G. C2h3o2 mass spectrometry analysis revealed that the cho compound had a molar mass of 180 g/mol. What is the molecular formula for this compound? enter as c#h#o# (e. G. C2h3o2).

Answer 1

The empirical formula of a compound can be determined by dividing the number of moles of each element by the smallest number of moles of any element and rounding to the nearest whole number.

The 0.1014 g sample produced 0.1486 g CO2 and 0.0609 g H2O, which would mean that 0.1014 g / (12.01 + 16.00) = 0.0055 moles of carbon, and 0.1014 g / (1.01 + 16.00) = 0.0052 moles of hydrogen.

To find the empirical formula, divide each mole by the smallest mole: 0.0055 moles C / 0.0052 moles H = 1.06, so there is 1 mole of C and 1.06 moles of H. Rounding the moles of H to the nearest whole number gives 1 mole of H.

The empirical formula for the compound is therefore C1H1O.

The molecular formula for the compound can be found by dividing the molar mass of the compound by the empirical formula mass and rounding to the nearest whole number.

The empirical formula mass is 12.01 + 1.01 = 13.02 g/mol.

180 g/mol / 13.02 g/mol = 13.79. Rounding to the nearest whole number gives 14, so the molecular formula for the compound is C14H14O.