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Name: Answer Key Period: ______Date: ______Chem B odds for HW and evens for review

WS 4.2: Empirical Problems

Directions: Determine the empirical formula for the following substances. If a molecular formula cannot be reduced, write “cannot be reduced in the box for empirical formula”

Molecular Formula Empirical Formula Molecular Formula Empirical Formula

1) C6H6 CH 2) C10H18 C5H9

3) C8H18 C4H9 4) C7H15O2 Not reducible

5) WO2 Not reducible 6) N2H4 NH2

7) C2H6O2 CH3O 8) P3F6 PF2

9) X39Y13 X3Y 10) IF5 Not reducible 11) C4H10 C2H5 12) N2O5 Not reducible 13) C6H12O6 CH2O 14) N2O4 NO2 15) P2F4 PF2 16) SF6 Not reducible

17) SO3 Not reducible 18) N2Cl4 NCl2

19) N2Br4 NBr2 20) P2O5 Not reducible

Directions: Solve the following problems. You may need to use a separate sheet of paper.

1) What is the empirical formula for a compound which 3) Barry Um has a sample of a compound which weighs 200 contains 0.0134 g of iron, 0.00769 g of sulfur and 0.0115 g of grams and contains only , , and oxygen? nitrogen. By analysis, he finds that it contains 97.56 grams of carbon, 4.878 g of hydrogen, 52.03 g of oxygen and 45.53

g of nitrogen. Find its empirical formula.

3 FeSO

C5H3N2O2

2) A compound is found to contain 53.7 % iron and 46.27 % sulfur. Find its empirical formula. 4) What is the empirical formula for a compound which

contains 80.3% zinc and the rest is oxygen?

Fe2S3

ZnO

5) Rubbing alcohol was found to contain 60.0 % carbon, 13.4 9) Give the name and empirical formula of a compound % hydrogen, and the remaining mass was due to oxygen. which contains 0.463 g Thallium, 0.0544 g of carbon, What is the empirical formula of rubbing alcohol? 0.00685g of hydrogen and 0.0725g oxygen.

C3H8O TlC2O2H3

10) A compound was analyzed and found to contain 13.5 g Ca, 10.8 g O, and 0.675 g H. What is the empirical formula of 6) If 4.04g of Nitrogen combine with 11.46g Oxygen to the compound? If the compound is ionic, what is the produce a compound with a molar mass of 108.0 g/mol, correct ? what is the empirical formula of this compound?

2 2 CaO H N2O5 But knowing what we know about ionic compounds the correct chemical formula would be:

Ca(OH)2

11) What is the simplest formula of a substance which contains about 94% sulfur and about 6% hydrogen?

7) What’s the empirical formula of a containing 18.7% lithium, 16.3% carbon, and 65.0% oxygen? SH2

Li2CO3

12) Find the empirical formula for a substance with the 8) A sample of indium chloride weighing 0.5000 g is found to following mass percentages: contain 0.2404 g of chlorine. What is the empirical formula Al = 22%, P = 25%, and O = 53%. of the indium compound?

AlPO4 InCl3