In a complete combustion process, the products would be 1 mol of CO2 and 1 mol of H2O. In order to find out the amount of naphthalene reacted in the combustion process, you would need the relation of the mass of carbon with carbon dioxide (1 mol of CO2 = 1 mol C) and also the mass of hydrogen with water (1 mol H2O = 2 mol H). Convert the mass of CO2 and H2O given to moles of Carbon and Hydrogen respectively. You would get 0.1998 mol C and 0.1598 mol H. Then you would need to divide each with the smallest amount of moles present which is 0.1598. Thus you would get a ratio of 1.25 C: 1 H. Multiply this ratio with 4 in order to make it whole number. The empirical formula would be C5H4.
