Practice Exam B

1 Practice Exam 1B 1. What is the best answer to report for 3478 1164 200 0354 .. . .? × + (A) 2.378 (B) 2.3782 (C) 2 (D) 2.4 (E) 2.38 2. The density of a gas is 1.96 g/L at 1.00 atm and 0 °C. What is the density of this gas at 0.855 atm and 25.0 °C ? (A) 0.00276 g/L (B) 0.0423 g/L (C) 0.651 g/L (D) 1.54 g/L (E) 1.82 g/L 3. A sheet of Xerox paper measures 8.5 × 11.0 inches. What is the surface area of one side of the paper in cm 2 ? (A) 6.03 × 10 2 cm 2 (B) 94 cm 2 (C) 6 × 10 2 cm 2 (D) 6.0 × 10 2 cm 2 (E) 93.5 cm 2 4. You are given a 0.252 g sample of a copper-containing alloy and asked to determine the weight percent of copper. After dissolving the metal in acid, you add an excess of KI, and the Cu 2+ and I - ions undergo the reaction 2Cu 2+ (aq) + 5I - (aq) ? CuI(s) + I 3 - (aq) The liberated I 3 - is titrated with sodium thiosulfate according to the equation I 3 - (aq) + 2S 2 O 3 2- (aq) ? S 4 O 6 2- (aq) + 3I - (aq) If 26.32 mL of 0.101 M Na 2 S 2 O 3 is required for titration to the equivalence point, what is the weight percent of Cu in the alloy? (A) 74.3% (B) 67.1% (C) 93.4% (D) 45.8% (E) 33.6% 2 5. A 1.00 g sample of KMnO 4 (M = 158 g/mol) was completely decomposed by heating, yielding 99.2 mL of oxygen collected over water at 22 o C and a total pressure of 755 mmHg. At 22 o C the vapor pressure of water is 20 mm Hg. Which of the following equations best fits this data for the decomposition reaction? (A) 2KMnO 4 (s) ? K 2 MnO 4 (s) + MnO 2 (s) + O 2 (g) (B) 2KMnO 4 (s) ? K 2 MnO 3 (s) + MnO(s) + 2O 2 (g) (C) 7KMnO 4 (s) ? 3K 2 MnO 4 (s) + Mn 3 O 4 (s) + 6O 2 (g) (D) 8KMnO 4 (s) ? 4K 2 MnO 4 (s) + 2Mn 2 O 3 (s) + 5O 2 (g) (E) 9KMnO 4 (s) ? 3K 3 MnO 4 (s) + 2Mn 3 O 4 (s) + 8O 2 (g) 6. Which combination represents a 57 Fe 3+ ion? (p = protons, n = neutrons, e = electrons) (A) 26p, 31n, 26e (B) 26p, 31n, 29e (C) 26p, 31n, 23e (D) 57p, 26n, 23e (E) 57p, 26n, 54e 7. The atomic mass of Ga is 69.72. There are only two naturally occurring isotopes of gallium, 69 Ga with a mass of 69.0 and 71 Ga with a mass of 71.0. The natural abundance of the 71 Ga isotope must be approximately (A) 20%. (B) 60%. (C) 80%. (D) 40%. (E) 50%. 8. Calculate the standard enthalpy change for the reaction CH 4 (g) + 3Cl 2 (g) ? CHCl 3 (g) + 3HCl(g) using the following information: HCl(g) ? ½ H 2 (g) + 1/2Cl 2 (g) ?H o = +92.3 kJ C(s) + 2H 2 (g) ? CH 4 (g) ?H o = -74.8 kJ C(s) + 1/2H 2 (g) + 3/2Cl 2 (g) ? CHCl 3 (g) ?H o = -103.1 kJ A) -120.6 kJ B) -212.9 kJ C) -305.2 kJ D) -454.8 kJ E) +212.9 kJ 3 9. Assume that 0.25 mole of H 2 CO 3 is produced in the following reaction: CO 3 2- (aq) + 2 H 3 0 + (aq) ??? H 2 CO 3 (aq) + 2 H 2 O (l) Which statement(s) is(are) correct? 1. 0.50 mole of H 3 O + reacted to produce H 2 CO 3 . 2. 6.022 x10 23 CO 3 2- ions reacted to produce H 2 CO 3 . 3. The H 2 CO 3 produced weighs 15.5 g. (A) 1 only (B) 2 only (C) 3 only (D) 1 and 3 only (E) 1, 2, and 3 10. The total number of atoms in 1.00 g of CaCO 3 (molar mass = 100.0 g/mol) is (A) 2.41 × 10 23 . (B) 3.01 × 10 23 . (C) 3.01 × 10 22 . (D) 2.41 × 10 22 . (E) 1.81 × 10 22 . 11. A sample of fructose, a fruit sugar, C 6 H 12 O 6 , that contains 48 g of carbon also contains how many grams of hydrogen? (A) 16 (B) 24 (C) 8 (D) 32 (E) 12 12. Cubane is a compound composed of only C and H. It contains 92.26% C by mass. What is its empirical formula? (A) CH (B) C 3 H 4 (C) C 2 H 5 (D) CH 2 (E) C 2 H 3 13. The hormone testosterone has a molecular mass of 288.4 amu and contains 79.12% carbon by mass. How many carbon atoms are in each testosterone molecule? (A) 21 (B) 23 (C) 28 (D) 17 (E) 19 4 14. 2Al(s) + 6HCl(aq) ??? 2AlCl 3 (aq) + 3H 2 (g) According to the equation above, how many grams of aluminum are needed to react with 1.16 mol of hydrochloric acid? (A) 10.4 (B) 15.7 (C) 23.6 (D) 1.16 (E) 18.2 15. Which of the following is a weak electrolyte in aqueous solution? (A) H 2 SO 3 (B) HBr (C) HClO 4 (D) NaOH (E) HNO 3 16. When a solution of lithium chloride and a solution of ammonium sulfate are mixed, (A) a precipitate forms. (B) a new salt is formed. (C) a gas is evolved. (D) an acid and a base are formed. (E) no reaction occurs. 17. The net ionic equation for the reaction of phosphoric acid with a dilute solution of calcium hydroxide to form a precipitate is (A) 2 H 3 PO 4 (aq) + 3 Ca 2+ (aq) + 6 OH - (aq) ??? Ca 3 (PO 4 ) 2 (s) + 6 H 2 O(l). (B) 2 H 3 PO 4 (aq) + 3 Ca 2+ (aq) + 6 OH - (aq) ??? 3Ca 2+ (aq) + 2 PO 4 3- (aq) + 6 H 2 O (l). (C) 2H + (aq) + 4H 2 PO 4 - (aq) + 3Ca 2+ (aq) + 6OH - (aq) ??? Ca 3 (PO 4 ) 2 (s) + 6H 2 O(l). (D) 6H + (aq) + 2PO 4 3- (aq) + 3Ca 2+ (aq) + 6OH - (aq) ??? Ca 3 (PO 4 ) 2 (s) + 6H 2 O(l). (E) 2H 3 PO 4 (aq) + 3Ca(OH) 2 (aq) ??? Ca 3 (PO 4 ) 2 (s) + 6 H 2 O(l). 18. Which of the following reactions is an oxidation-reduction reaction? (A) AgNO 3 + KI ??? AgI + KNO 3 (B) CaCO 3 + 2HCl ??? CaCl 2 + H 2 O + CO 2 (C) H 2 SO 4 + 2NaOH ??? Na 2 SO 4 + 2H 2 O (D) CaO + SO 3 ??? CaSO 4 (E) NH 4 NO 3 ??? N 2 O + 2 H 2 O 5 19. In which of the following compounds does the underlined element have an oxidation number of +2? (A) CrO 2 Cl 2 (B) HNO 2 (C) PH 4 . (D) Zn(OH) 4 2- (E) NO 2 20. A certain aqueous solution of FeCl 3 has a density of 1.19 g/mL and contains 20.0% (by mass) FeCl 3 (M w = 162 g/mol). What is the concentration of this solution? (A) 0.0282 M (B) 0.163 M (C) 1.27 M (D) 1.47 M (E) 7.35 M 21. If the standard enthalpies of formation of CO 2 (g), H 2 O(l), and toluene, C 7 H 8 (l) are -393.5, - 285.8, and + 12.0 kJ/mol, respectively, what is the standard enthalpy of combustion of toluene? (A) -3886 kJ/mol (B) -667.3 kJ/mol (C) -3910 kJ/mol (D) -5029 kJ/mol (E) -691.3 kJ/mol 22. Which one of the following combinations of names and formulas of ions is incorrect? (A) O 2- oxide (B) Cd 2+ cadmium (C) ClO 3 - chlorate (D) HCO 3 - hydrogen carbonate (E) NO 2 - nitrate 23. Assume you place 0.167 g of a gaseous compound in a 0.346 L flask. It exerts a pressure of 0.427 atm at 30 o C. What is the correct formula of the compound? (A) C 2 H 6 (B) C 2 H 4 (C) C 2 H 2 (D) C 6 H 6 (E) C 3 H 8 6 24. An important reaction sequence in the industrial production of nitric acid is the following: N 2 (g) + 3H 2 (g) ? 2NH 3 (g) 4NH 3 (g) + 5O 2 (g) ? 4NO(g) + 6H 2 O(l) Starting from 20.0 mol of nitrogen gas in the first reaction, how many moles of oxygen gas are required in the second one? (A) 12.5 (B) 20.0 (C) 25.0 (D) 50.0 (E) 100 25. The value of ?H? for the reaction below is ?1107 kJ: )(2)()(2 2 sBaOgOsBa ?+ How many kJ of heat are released when 15.75 g of Ba(s) (molar mass = 137.3 g/mol) reacts completely with oxygen to form BaO(s)? (A) 20.8 (B) 63.5 (C) 114 (D) 70.3 (E) 35.1 dotie Microsoft Word - Practice Exam 1B.doc