Empirical Formulas Worksheet 1. The molecular formulas of some substances are as follows.  Write their empirical formulas. (a) Acetylene, C2H2 (used in oxyacetylene torches) (b) Glucose, C6H12O6 (the chief sugar in blood) (c) Octane, C8H18 (a component of gasoline) (d) Ammonium nitrate, NH4NO3 (a component of fertilizer) 2. A radioactive form of sodium pertechnetate is used as a brain-scanning agent in medical diagnosis. An analysis of a 0.9872 gram sample found 0.1220 grams of sodium and 0.5255 grams of technetium. The remainder is oxygen. Calculate the empirical formula of sodium pertechnetate. (Use the value of 98.907 as the atomic weight of Tc and arrange the atomic symbols in the formula in the order NaTcO.) 3. Potassium persulphate (Anthion) is used in photography to remove the last tracers of hypo from photographic papers and plates. A 0.8162 gram sample was found to contain 0.2361 grams of potassium and 0.1936 grams of sulphur; the rest was oxygen. The formula weight of this compound was measured to be 261. What are the empirical and molecular formulas of potassium persulphate? (Arrange the atomic symbols in the formulas in the order KSO.) 4. Adenosine triphosphate (ATP) is an important substance in all living cells. A sample with a mass of 0.8138 grams was analyzed and found to contain 0.1927 grams of carbon, 0.02590 grams of hydrogen, 0.1124 grams of nitrogen, and 0.1491 grams of phosphorus. The remainder was oxygen. Its formula weight was determined to be 507. Calculate the empirical and molecular formulas of adenosine triphosphate. (Arrange the atomic symbols in alphabetical order in the formula.) 5. Realgar (re-Al-gar) is a deep red pigment used in painting. A 0.6817 grams sample was found to contain 0.4774 grams of arsenic; the remainder was sulphur. The formula weight of realgar was found to be 428. What are the empirical and molecular formulas of this pigment? (Arrange the symbols in the order AsS.) 6. Isobutylene is a raw material for making synthetic rubber. A sample with a mass of 0.6481 grams was found to contain 0.5555 grams of carbon; the rest was hydrogen. Its formula weight was determined to be 56.12. What are the empirical and molecular formulas of isobutylene? (Place the atomic symbols in the formulas in the order CH.) 7. Cyanuric acid is used for such different purposes as making synthetic sponges and killing weeds. A sample with a mass of 0.5627 grams was found to contain 0.1570 grams of carbon, 0.01317 grams of hydrogen, and 0.1832 grams of nitrogen, with the balance being oxygen. Its formula weight was found to be 129. Calculate the empirical and molecular formulas of cyanuric acid, arranging the atomic symbols in alphabetical order. 8. C.I.Pigment Yellow 45 ("sideran yellow") is a pigment used in ceramics, glass, and enamel. When analyzed, a 2.164 grams sample of this substance was found to contain 0.5259 grams of Fe and 0.7345 grams of Cr. The remainder was oxygen. Calculate the empirical formula of this pigment. 9. The composition of nicotine is 74.0% C, 8.7% H, and 17.3% N.  The molecular mass of nicotine is 162.  What is its molecular formula? 10. One compound of mercury with a formula weight of 519 contains 77.26% Hg, 9.25% C, and 1.17% H, and the remainder is oxygen. Calculate its empirical and molecular formulas, arranging the atomic symbols in the order Hg, C, H, and O. 11. The chief compound in the mineral celestine consists of strontium, sulphur, and oxygen. The percentage composition is 47.70% Sr and 17.46% S; the remainder being oxygen. Its formula weight is 184. What are the empirical and molecular formulas of this compound? (Arrange the atomic symbols in the formulas in the order Sr, S, and O.) 12. One of the most deadly poisons, strychnine, has a formula weight of 334 and the composition 75.42% C, 6.63% H, 8.38% N; the rest is oxygen. Calculate the empirical and molecular formulas of strychnine, arranging the atomic symbols in alphabetical order. 13. A sample of a liquid consisting of only C, H and O and having a mass of 0.5438 grams was burned in pure oxygen and 1.039 grams of CO2 and 0.6369 grams of H2O were obtained. What is the empirical formula of the compound?