CH4O First, look up the atomic weights of the involved elements Atomic weight carbon = 12.0107 Atomic weight hydrogen = 1.00794 Atomic weight oxygen = 15.999 Now determine the number of moles of each element you have moles carbon = 37.5 / 12.0107 = 3.1222 mol moles hydrogen = 12.5 / 1.00794 = 12.4015 moles oxygen = 50 / 15.999 = 3.1252 So we have the ratio 3.1222 : 12.4015 : 3.1252 We need to find a ratio of small integers that closely matches the above ratio. First, divide all values by 3.1222 (selected because it's the smallest), giving 1 : 3.972 : 1.001 All of the above values are close to integers, so the ratio is 1 : 4 : 1 This indicates that the empirical formula is CH4O