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

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 ?

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

If only B and H, then 18.90% H Assume g of the compound  g of B and g of H. Convert to moles  moles B and 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?

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.?

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

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

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

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

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

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