Carver Engineering and Science AP Chemistry – Mr. Wagenhoffer AP Problem Set #3 Name:______________________________________________________________________________________ Date:_______________________________ 1. How many grams of calcium nitrate, Ca(NO3)2, contains 24 grams of oxygen atoms? (A) 164 grams (B) 96 grams (C) 62 grams (D) 50 grams (E) 41 grams 2. The mass of element Q found in 1.00 mole of each of four different compounds is 38.0 grams, 57.0 grams, 76.0 grams, and 114 grams, respectively. A possible atomic weight of Q is (A) 12.7 (B) 19.0 (C) 27.5 (D) 38.0 (E) 57.0 3. The simplest formula for an oxide of nitrogen that is 36.8 percent nitrogen by weight is (A) N2O (B) NO (C) NO2 (D) N2O3 (E) N2O5 4. Aluminum reacts with sulfuric acid, H2SO4, to form aluminum sulfate, Al2(SO4)3, and hydrogen gas, H2. Give the sum of all coefficients (all reactants and products) for this balanced chemical reaction. (A) 4 (B) 5 (C) 6 (D) 9 (E) 12 5. There are three naturally occurring isotopes of oxygen: oxygen-16, oxygen-17, and oxygen-18. The atomic mass of oxygen is 16.00 amu. From these data, it may be concluded that… (A) most of the oxygen atoms are 17O. (B) most of the oxygen atoms are 18O. (C) very few of the atoms are 17O and 18O. (D) there is an equal abundance of all three isotopes in nature. (E) more than half of the atoms are 18O. 6. Analysis of a sample of an oxide of chromium is reported as 26 g of chromium and 12 g of oxygen. From these data, determine the empirical formula of this compound. (A) CrO (B) Cr2O3 (C) CrO3 (D) CrO2 (E) Cr4O6 7. A 100.0 g sample of impure calcium carbonate was heated. It decomposed to form carbon dioxide gas and calcium oxide. After heating, the solid residue weighed 78 grams. What was the percent of calcium carbonate by mass in the original sample? (A) 10 % (B) 15 % (C) 25 % (D) 50 % (E) 75 % 8. A solution contains 0.10 mol of Pb(NO3)2 and 0.050 mol of BaI2. How many moles of PbI2 will precipitate? (A) 0.050 (B) 0.10 (C) 0.15 (D) 0.20 (E) none of these 9. Naturally occurring copper exists in two isotopic forms: 63Cu and 65Cu. The atomic mass of copper is 63.55 amu. What is the approximate natural abundance of 63Cu? (A) 63 % (B) 90 % (C) 70 % (D) 50 % (E) 30 % 10. Naturally occurring element X exists in three isotopic forms: X-28 (27.977 amu, 92.23 % abundance), X-29 (28.976 amu, 4.67 % abundance), and X-30 (29.974 amu, 3.10 % abundance). What is the identity of element X? (A) Cu (B) Al (C) Ni (D) Si (E) Sr 11. The molar mass of the compound formed by potassium and oxygen is… (A) 94.2 g/mol (B) 71.1 g/mol (C) 55.1 g/mol (D) 87.1 g/mol (E) 133.3 g/mol 12. In the balanced equation for the reaction: xP4O6 (s) + yH2O (l) ======> zH3PO4 (aq) if x = 2, the coefficient z equals… (A) 2 (B) 4 (C) 6 (D) 10 (E) none of these