Additional Practice: pgs 10-11 A student conducted an experiment to determine whether the sample was Iron (II) Iodide or Iron (III) Iodide. By heating the sample, the iodine is released and the iron is left in the dish. The student weighed an evaporating dish and the sample, and then proceeded to heat the sample to drive off the iodide. After ten minutes, the sample was cooled and weighed again. The data from this experiment is provided in the table below. Use this data to answer the analysis questions that follow.

Data Table Mass of the empty evaporating dish 21.5g Mass of the original sample 17.4g Total mass of dish and sample before heating 38.9g Total mass of dish and remaining solid after heating 23.7g

Analysis Questions: (Show work) Determine the difference in mass before and after heating. (This is the mass of the iodine that was driven off by heating.) Mass of iodine :   Subtract the mass of iodine from the mass of the original sample. (This is the mass of the remaining solid, and is the mass of iron in the sample.) Mass of iron: 38.9 g - 23.7 g 15.2 g 17.4 g - 15.2 g 2.2 g

15.2 g x 1 mol = mol 0.12 126.9 g 2.2 g = mol x 1 mol 0.038 55.8 g Convert the mass of iodine into moles of iodine. Show your work.   Convert the mass of iron into moles of iron. Show your work. 15.2 g x 1 mol = mol 0.12 126.9 g 2.2 g = mol x 1 mol 0.038 55.8 g

0.12 mol I ~ 3 mol I 1 mol Fe 0.038 mol Fe Fe 3+ I - Vs. Fe 2+ I - To determine the ratio of iodine to iron in the original sample, divide the moles of iodine by the moles of iron. Round your answer to the nearest whole number, this is the mole ratio; use it to construct the formula for the iron and iodine compound in your sample. Mole ratio: I / Fe Formula: FeI   What are the two possible formulas for the compounds of iron with iodine? ___________ 0.12 mol I ~ 3 mol I 1 mol Fe 0.038 mol Fe Iron (III) iodide Iron (II) iodide 3 Fe 3+ I - Vs. Fe 2+ I - FeI2