Question

A student has a sample of an unknown inorganic compound that contains only carbon, oxygen, and nitrogen. They perform a combustion analysis on a 0.230 g sample of the compound, which yields 0.535 g of CO2 and 0.184 g of H2O. Additionally, when the compound is analyzed using a mass spectrometer, the mass spectrum shows a molecular ion peak at m/z = 42. Determine the empirical and molecular formulas of this compound.

Answer 1

First, we need to determine the moles of carbon and oxygen in the compound using the masses of CO2 and H2O produced.1. Moles of carbon:From the combustion analysis, we know that 0.535 g of CO2 is produced. The molar mass of CO2 is 12.01 g/mol  C  + 2 * 16.00 g/mol  O  = 44.01 g/mol. Moles of carbon = mass of CO2 / molar mass of CO2Moles of carbon = 0.535 g / 44.01 g/mol = 0.01216 mol2. Moles of oxygen:From the combustion analysis, we know that 0.184 g of H2O is produced. The molar mass of H2O is 2 * 1.01 g/mol  H  + 16.00 g/mol  O  = 18.02 g/mol.Moles of oxygen = mass of H2O / molar mass of H2OMoles of oxygen = 0.184 g / 18.02 g/mol = 0.01022 molNow, we need to find the moles of nitrogen in the compound. We know the total mass of the compound is 0.230 g.Mass of nitrogen = total mass - mass of carbon - mass of oxygenMass of nitrogen = 0.230 g -  0.01216 mol * 12.01 g/mol  -  0.01022 mol * 16.00 g/mol Mass of nitrogen = 0.230 g - 0.146 g - 0.163 g = -0.079 gThe mass of nitrogen is negative, which indicates an error in the analysis or a mistake in the problem statement. Please recheck the given data and try again.