1. Lecture 89/17/04 1 rst Exam next Friday  Review Session Seminar next Monday

2. Quiz 3 1. Give the name of each of the following 1. Ba(OH) 2 2. FeCl 2 2. What is the percentage of carbon in CO 2 ?

3. Use the weight percentage to derive the EMPIRICAL or SIMPLEST formula. CH 4 : CH 4 : 75% C and 25% H by weight C 2 H 8 : C 2 H 8 : 75% C and 25% H by weight C 3 H 12 : C 3 H 12 : 75% C and 25% H by weight Empirical and Molecular Formulas

4. If only B and H, then 18.90% H Assume 100.0 g of the compound  81.10 g of B and 18.90 g of H. Convert to moles  7.502 moles B and 18.75 moles of H Find whole number ratio of elements  Always divide by the smaller number.  2.5 mol H/1.0 mol B = 5 mol H to 2 mol B  EMPIRICAL FORMULA = B 2 H 5 A compound of B and H is 81.10% B What is its empirical formula?

5. Now that we know that its empirical formula is B 2 H 5. Is the molecular formula: B 2 H 5, B 4 H 10, B 6 H 15, B 8 H 20, etc.?

6. Need to do an experiment Experiment shows that it has a molar mass of 53.3 g/mol Compare with the mass of B 2 H 5 (26.66 g/unit) Molecular formula = B 4 H 10

7. Reaction of Sn and I 2 is done using excess Sn. Mass of Sn in the beginning = 1.056 g Mass of iodine (I 2 ) used = 1.947 g Mass of Sn remaining = 0.601 g Determine the formula of a compound of Sn and I using the following data

8. Find the mass of Sn that combined with 1.947 g I 2. Mass of Sn initially = 1.056 g Mass of Sn recovered = 0.601 g Mass of Sn used = 0.455 g Find moles of Sn used: Tin and Iodine Compound

9. Now find the number of moles of I 2 that combined with 3.83 x 10 -3 mol Sn. Mass of I 2 used was 1.947 g. How many mol of iodine atoms ? = 1.534 x 10 -2 mol I atoms

10. Tin and Iodine Compound Now find the ratio of number of moles of moles of I and Sn that combined. Empirical formula is SnI 4

11. Thallium has an atomic weight of 204.38 amu, and has 2 isotopes, Tl-203 and Tl-205. What are the abundances of these isotopes ?