Question

3. Acrylic acid, used in the manufacture of some plastics, has the composition 50.0% C,

5.6% H, and 44.4% O by mass. What is the empirical formula?

4. Urea contains C, H, N, and O. A 2.54 gram sample of urea is found to contain 0.51 g carbon,

0.17 g of hydrogen, and 1.19 g of nitrogen. What is the empirical formula of urea?

5. Putrescine, a substance produced by decaying animals, is composed of 54.5 % carbon,

13.6% hydrogen, and 31.8 % nitrogen by mass. If putrescine has a molar mass of 88 g/mol, determine its molecular formula.

6. A compound has a molar mass of 134 g/mol. If a 15.0 gram sample contains 5.15 g sodium,

2.69 g carbon, and 7.16 g oxygen, what is the name of this compound?

% Composition, Empirical & Molecular Formula

1. Calculate the mass percent of each element in the following compounds:

(a) Ca(C2H3O2)2

(b) ammonium sulfide

2. How many grams of iron are present in 10.0 grams of iron III oxide (rust)?

3. What are the empirical formulas for compounds with the following compositions?

(a) 2.1 percent hydrogen, 32.6 percent sulfur, and 65.3 percent oxygen

(b) 50.0% carbon, 5.6% hydrogen, and 44.4% oxygen

4. Analysis of an unknown compound determines that it contains 2.84 grams of

phosphorous and 3.66 grams of oxygen. Determine its empirical formula.

5. A carbohydrate is a compound which contains only carbon, hydrogen, and oxygen. A

particular carbohydrate with a molar mass of 179 g is composed of 40% carbon and 6.7% hydrogen by mass. Determine the molecular formula of this compound.

6. Caffeine is composed of 49.5% carbon, 5.15% hydrogen, 28.9% nitrogen, and 16.5% oxygen

by mass. If its molar mass is 194.2 g/mol, determine the molecular formula of caffeine.

Answer 1

Empirical formula of Acrylic acid = C3H4O2.