Chapter 3.1-3.5 Review packet Balancing and Stoichiometry

# Element x has three naturally occurring isotopes the

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23. Element X has three naturally occurring isotopes. The mass (amu) and % abundance of the isotopes are: 37.919 (5.07%), 39.017 (15.35%), and 42.111 (79.58%). What is the average atomic mass (amu) of element X? a. 41.42 b. 39.68 c. 39.07 d. 38.64 e. 33.33 24. The mass % of C in CH 4 is __________. 25. Which of the following, strictly speaking, does not have a molecular weight? 26. There are __________ mol of carbon atoms in 4 mol of dimethylsulfoxide (C 2 H 6 SO). 27. How many hydrogen atoms are there in 25 molecules of C 4 H 4 S 2 ? a. 25 b. 3.8 x 10 24 c. 6.0 x 10 25 d. 100 e. 1.5 x 10 25

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28. How many molecules of CH 4 are in 48.2 g of this compound? 29. A sample of CH 2 F 2 with a mass of 19 g contains __________ atoms of F. 30. How many oxygen atoms are contained in 2.74 g of Al 2 (SO 4 ) 3 ? 31. What is the empirical formula of a compound that contains 27.0% S, 13.4% O, and 59.6% Cl? a. SOCl b. SOCl 2 c. S 2 OCl d. SO 2 Cl e. ClSO 4 32. What is the empirical formula of a hydrocarbon that is 89.94% by mass carbon? 33. What is the empirical formula for a compound that contains 29% Na, 41% S, and 30% O by mass? 34. A compound contains 40.0% C, 6.71% H, and 53.29% O by mass. The molecular mass of the compound is 60.05 amu. The molecular formula of this compound is __________.
35. The empirical formula of a compound is NO 2 and the formula weight is (89 ñ 6) amu. The molecular formula is ____________. a. NO b. NO 2 c. N 2 O d. N 2 O 4 e. N 3 O 6

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