Question

A chemistry student was given a sample of an unknown compound. The student performed an analysis on the sample using mass balance calculations and obtained the following data: the sample had a mass of 2.64 g and contained 1.32 g of carbon, 0.22 g of hydrogen, and 0.88 g of oxygen. What is the molecular formula of the unknown compound?

Answer 1

To determine the molecular formula of the unknown compound, we first need to find the empirical formula. The empirical formula is the simplest whole-number ratio of the elements in the compound. 1. Calculate the moles of each element in the compound:Carbon: 1.32 g /  12.01 g/mol  = 0.11 molHydrogen: 0.22 g /  1.01 g/mol  = 0.218 molOxygen: 0.88 g /  16.00 g/mol  = 0.055 mol2. Divide each value by the smallest number of moles to find the mole ratio:Carbon: 0.11 mol / 0.055 = 2Hydrogen: 0.218 mol / 0.055 = 3.96  4Oxygen: 0.055 mol / 0.055 = 13. The empirical formula is C2H4O.Now, we need to find the molecular formula. To do this, we need to determine the molecular weight of the unknown compound. Unfortunately, we do not have enough information to determine the molecular weight. If we had the molecular weight, we could divide it by the empirical formula weight and multiply the empirical formula by the resulting factor to obtain the molecular formula.Without the molecular weight, we can only determine the empirical formula, which is C2H4O.