Name,

12

Prelab for Experiment 4: The Atomic Theory of Matter

1. Demonstrate the Law of Multiple Proportions with the following data:

a. Iron forms two compounds with chlorine, compound X and compound Y. When 3.00 g of

compound X was analyzed, it was found that 1.68 g of Cl combined with 1.32 g of Fe. When

5.00 g of compound Y was analyzed, it was found that 3.28 g of Cl combined with 1.72 g of Fe.

To illustrate the Law, one needs to know how much of one element combines with the

same mass as the other element in each compound, but the data above give different masses for

both Fe and Cl. One way to standardize the data is to find out how much of one element, say Cl,

combines with exactly 1 g of the other, say Fe. This can be done by a simple proportion method

("if 1.75 g of Cl combines with 1.25 g of Fe, how many g of Cl would combine with

1.00 g of Fe...") Do this for both compounds, X and Y.

b. You now have the mass of chlorine that combines with 1.00 g of Fe for each of the two

different compounds. If the data obey the Law of Multiple Proportions, the ratio of the chlorine

mass in compound X to the chlorine mass in compound Y should be a whole number or a simple

fraction (i.e., 1.5 would be 3/2; 1.33 would be 4/3). Do the above data support the Law?

2. In this experiment, the mass of Cu is determined directly by weighing. How will the mass of

chloride be determined?

3. What is acetone used for in this experiment?