AP Chemistry - Emprical Formulas Worksheet | |

1. |
The molecular formulas of some substances are as follows.
Write their empirical formulas. (a) Acetylene, C _{2}H_{2} (used in oxyacetylene
torches)(b) Glucose, C _{6}H_{12}O_{6} (the
chief sugar in blood)(c) Octane, C _{8}H_{18} (a component of
gasoline)(d) Ammonium nitrate, NH_{4}NO_{3} (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 CO_{2} and 0.6369 grams of H_{2}O were obtained. What
is the empirical formula of the compound? |

14. |
When a 3.00 grams sample of a compound containing only
C, H, and O was completely burned, 1.17 grams of H_{2}O and 2.87
grams of CO_{2} were formed. What is the simplest formula of the
compound? |

15. |
During early research on a sex hormone, thousands of
litres of urine collected from pregnant mares were processed to isolate less
than a gram of the hormone. It was found to consist entirely of carbon, hydrogen,
and oxygen. When a sample of this hormone with a mass of 6.853 mg was burned,
20.08 mg CO_{2} and 5.023 mg of H_{2}O were obtained. The
formula weight of the substance was found to be 270. What is its molecular
formula? |

16. |
Vitamin D activity is shown by several compounds consisting
wholly of carbon, hydrogen, and oxygen. When a sample of one of them with
a mass of 5.676 mg was burned in oxygen, 17.536 mg of CO_{2} and
5.850 mg of H_{2}O were obtained. The formula weight was found to
be 385. What is the molecular formula of this compound? |

17. |
Progesterone, the so-called pregnancy hormone, was
isolated by Adolf Butenandt in 1934. By extracting the ovaries of 50,000
sows, Butenandt was able to isolate 20 mg of the pure hormone. Microanalysis
of a 0.0050 gram sample of this material by combustion analysis led to the
production of 0.0147 grams of CO_{2} and 0.0043 grams of H_{2}O. |