CHEMISTRY 1710 - Practice Exam #2 (KATZ) Section 1 - This section of the exam is multiple choice. Choose the BEST answer from the choices which are given and write the letter for your choice in the space provided. All questions are equally weighted and there is no penalty for guessing. (Please include any calculations in the space provided.) 1. Which of the following is the empirical formula for hexane, C 6 H 14? A. C 12 H 28 B. C 6 H 14 C. C 3 H 7 D. CH 2.3 2. Which of the following is the formula for barium nitrite? A. Ba 3 N 2 B. BaNO 3 C. BN D. Ba(NO 2 ) 2 3. Which of the following is the formula for strontium nitride? A. Sr 3 N 2 B. Sr(NO 3 ) 2 C. SrN D. Sr 2 N 3 4. What is the correct name for MnBr 2. 2H 2 O? A. manganese bromide hydrate B. cobalt dichloride dihydrate C. manganese (I) bromide dihydrate D. manganese (II) bromide dihydrate 5. What is the name of the acid formed when HBr gas is dissolved in water? A. bromic acid B. bromous acid C. hydrobromic acid D. hydrobromous acid 6. Which one of the following combinations of names and formulas is incorrect? A. H 3 PO 4<---------------> phosphoric acid B. N 2 O 5 <------------------>dinitrogen pentaoxide C. NaHCO 3 <----------------->sodium carbonate D. H 2 CO 3<-------------------> carbonic acid
7. Kaolinite, a clay mineral with the formula Al 4 Si 4 O 10 (OH) 8, is used as a filler in slick-paper for magazines and as a raw material for ceramics. Analysis shows that 14.35 g of kaolinite contains 8.009 g of oxygen. Calculate the mass percent of oxygen in kaolinite. A. 24.80 mass % B. 30.81 mass % C. 34.12 mass % D. 55.81 mass % 8. What is the mass of 9.44 1024 molecules of NO2? The molar mass of NO2 is 46.01 g/mol. A. 205 g B. 294 g C. 721 g D. 341 g 9. How many moles of PCl3 contain 3.68 1025 chlorine atoms? A. 61.1 moles PCl3 B. 20.4 moles PCl3 C. 16.4 moles PCl3 D. 54.5 moles PCl3 10. Determine the molecular formula of a compound that has a molar mass of 183.2 g/mol and an empirical formula of C2H5O2. A. C2H5O2 B. C6H15O6 C. C3H7O3 D. C4H10O4 11. Which of the following solutions will have the highest concentration of chloride ions? A. 0.20 M NaCl B. 0.10 M MgCl2 C. 0.10 M AlCl3 D. 0.05 M CaCl2 12. How many milliliters of a 9.0 M H2SO4 solution are needed to make 0.35 L of a 3.5 M solution? A. 0. 14 ml B. 0.90 ml C. 140 ml D. 900 ml 13. Identify HCl. A) strong electrolyte, weak acid B) weak electrolyte, weak acid C) strong electrolyte, strong acid D) weak electrolyte, strong acid 14. Identify NaCl. A) weak acid B) weak electrolyte C) strong acid D) strong electrolyte
15. Which of the following pairs of aqueous solutions will form a precipitate when mixed? A) NH4NO3 + Li2CO3 B) Hg2(NO3)2 + LiI C) NaCl + Li3PO4 D) AgC2H3O2 + Cu(NO3)2 16. Identify the spectator ions in the following molecular equation. KBr(aq) + AgNO3(aq) AgBr(s) + KNO3(aq) A) Ag+ and Br- B) K+ and NO3 - C) K+ and Br- D) Ag+ and NO3-17. Give the net ionic equation for the reaction that occurs when aqueous solutions of H2SO4 and KOH are mixed. A) H+(aq) + OH-(aq) H2O(l) B) 2 K+(aq) + SO4 2- (aq) K2SO4(s) C) H+(aq) + OH-(aq) + 2 K+(aq) + SO4 2- (aq) H2O(l) + K2SO4(s) D) H2 2+ (aq) + OH-(aq) H2(OH)2(l) 18. The titration of 25.0 ml of an unknown concentration H2SO4 solution requires 83.6 ml of 0.12 M LiOH solution. What is the concentration of the H2SO4 solution (in M)? A) 0.20 M B) 0.40 M C) 0.10 M D) 0.36 M 19. Which of the following is an acid base reaction? A) C(s) + O2(g) CO2(g) B) 2 HClO4(aq) + Ca(OH)2(aq) 2 H2O(l) + Ca(ClO4)2(aq) C) Fe(s) + 2 AgNO3(aq) 2 Ag(s) + Fe(NO3)2(aq) D) MgSO4(aq) + Ba(NO3)2(aq) Mg(NO3)2(aq) + BaSO4(s) 20. Determine the oxidation state of Sn in Sn(SO4)2. A) +2 B) +4 C) +6 D) 0
21. What element is undergoing oxidation (if any) in the following reaction? Zn(s) + 2 AgNO3(aq) Zn(NO3)2(aq) + 2 Ag(s) A) Zn B) N C) O D) Ag 22. What is the oxidation number change for the bromine atom in the following unbalanced reduction half reaction: BrO 3 - (aq) + H + (aq) Br - (aq) + I A) -7 B) - 6 C) + 6 D) + 7 23. To what temperature must a balloon, initially at 25 C and 2.00 L, be heated in order to have a volume of 6.00 L? A) 993 K B) 403 K C) 75 K D) 894 K 24. How many moles of CO are contained in a 5.00 L tank at 155 C and 2.80 atm? A) 0.399 moles B) 1.10 moles C) 2.51 moles D) 0.455 moles 25. What is the volume of 5.60 g of O2 at 7.78 atm and 415K? A) 1.53 L B) 565 L C) 24.5 L D) 0.766 L 26. Which of the following samples will have the greatest volume at STP? A) 22 g CO B) 22 g He C) 22 g O2 D) 22 g Cl2 27. Place the following gases in order of increasing density at STP. N2 NH3 N2O4 Ar A) N2O4 < Ar < N2 < NH3 B) Ar < N2O4 < N2 < NH3 C) NH3 < Ar < N2 < N2O4 D) NH3 < N2 < Ar < N2O4
28. The density of a gas is 1.43 g/l at STP. What is the gas? A) Cl2 B) S C) O2 D) Ne 29. A 0.465 g sample of an unknown gas occupies 245 ml at 298 K and 1.22 atm. What is the molar mass of the unknown compound? A) 26.3 g/mol B) 33.9 g/mol C) 12.2 g/mol D) 38.0 g/mol Section 2 - Write balanced chemical equations which correspond to the following statements. 1. Aqueous copper (II) chloride reacts with aqueous sodium hydroxide to yield solid copper (II) hydroxide and aqueous sodium chloride. CuCl2 (aq) + 2 NaOH (aq)------------> Cu(OH)2 (s) + 2 NaCl (aq) 2. Solid boron(iii) oxide reacts with hydrofluoric acid to yield boron trifluoride gas and water. B2O3 (s) + 6 HF (aq) ------------> 2 BF3 (g) + 3 H2O (l) 3. Liquid benzene (C 6 H 6 ) reacts with oxygen gas to yield carbon dioxide and water. 2 C6H6 (l) + 15 O2 (g) ------------> 12 CO2 (g) + 6 H2O (l)
Section 3 - Calculations Involving Chemical Equations Consider the following reaction BaCl 2 (s) + H 2 SO 4 (l)--------------> BaSO 4 (s) + 2 HCl (g) A mixture of 2.65 g of BaCl 2 and 6.78 g of H 2 SO 4 are allowed to react. Molar masses: BaCl 2, 208.2324 H 2 SO 4, 98.078 BaSO 4, 233.43 HCl, 36.4606 1. How many grams of BaSO 4 could theoretically be produced from the 2.65 g of BaCl 2? 2.97 Answer: g 2. How many grams of BaSO 4 could theoretically be produced from 6.78 g of H 2 SO 4? c) Which is the limiting reagent in this reaction? Answer: g Answer: d) If 1.25 g of BaSO 4 is actually isolated, what is the percentage yield for the reaction? 16.1 BaCl2 42.1% Answer:
Section 4 - Calculations involving Solutions 1. Calculate the molarity of a solution prepared by dissolving 1.495 g of LiOH in enough water to give a final volume of 750. ml (Show work.) (1.495 g LiOH) x (1 mol/23.95 g LiOH) = 0.06242 mol LiOH (0.06242 mol LiOH)/(0.750 L) = 0.0832 M 2. Describe how you would prepare 250.0 ml of 3.000 M NaCl (M = 58.45 g/mol) from solid NaCl. (.2500 L soln) x (3.000 mol/1.000 L soln) x (58.45 g NaCl/1 mol NaCl) = 43.84 g NaCl 43.84 g NaCl is dissolved in enough water to make 250.0 ml.
Section 5 - Follow the directions to solve each problem. 1. An unknown liquid is vaporized in a 273-mL flask by immersion in a water bath at 99 C. The barometric pressure is 753 torr. If the mass of the liquid retained in the flask is 1.362 g, what is its molar mass? a. Find the number of moles of gas present using the ideal gas law..009 moles b. Using the measured mass of the liquid, find its molar mass. 150 g/mol 2. A small quantity of hydrogen was prepared by the addition of hydrochloric acid to zinc. 195 ml of hydrogen was collected over water at 25 C and 753 torr. from the reaction. (Pwater = 24 torr at 25 C) a. Write the balanced chemical equation for the reaction of zinc metal with hydrochloric acid to yield zinc chloride and hydrogen gas. Zn (s) + 2 HCl (aq)----> ZnCl2 (aq) + H2 (g) b. Correcting for water vapor pressure, what was the pressure of the hydrogen gas collected? 729 torr c. Using the ideal gas equation, calculate the number of moles of hydrogen gas collected?.00764 moles d. How many grams of zinc were present in the original reaction?.500 g