Sample Mid-term Examination Chemistry 217
Sample Mid-term Examination Chemistry 217 Multiple-choice Questions (2 marks each) Circle appropriate response. 1. A sky-blue aqueous solution was labeled "chromium(II) perchlorate". This solution contains the ions A) Cr2O2+ and ClO4–. B) Cr2O4+ and Cl–. C) Cr2+ and Cl–. D) Cr2+ and ClO4–. E) Cr3+ and ClO4–. 2. A) B) C) D) E) The name of the compound Hg2Cl2 is mercury(II) chloride. mercury(I) chloride. dimercury dichloride. mercury dichloride. dimercury chloride. 3. A) B) C) D) E) What is the charge on the anion in Cr2(SO3)3? –2 –6 –3 –4 +3 4. What volume of 0.202 M NaCl solution should you transfer so as to have a sample of solution that contains 0.354 mol NaCl? A) 1.75 L B) 5.71 mL C) 71.5 mL D) 1.75 mL E) 0.571 L 5. A) B) C) D) E) The prefix corresponding to the factor 10–9 is nano. pico. micro. kilo. milli. 6. A) B) C) D) E) What is the molar mass of sodium hydrogen carbonate? 107.0 g/mol 83.00 g/mol 68.01 g/mol 106.0 g/mol 84.01 g/mol 7. A) B) C) D) E) Which of the following is correct with respect to the reactions of PbO? PbO does not react with acid or base. PbO dissolves in water to give hydroxide ions. PbO reacts with base to give Pb(OH)4–. PbO reacts with water to give hydrogen gas. PbO is insoluble in base. 8. A) B) C) D) E) What type of reagent is required to convert HNO2 to NO2–? base acid reducing agent oxidizing agent neutralization reagent 9. A) B) C) D) E) Which of the following is soluble in water? lead(II) sulfate lead(II) nitrate lead(II) phosphate lead(II) chromate lead(II) bromide 10. How many moles of H+ ions are contained in 375 mL of an aqueous solution which is 0.200 M oxalic acid, H2C2O4(with two acidic protons)? A) 0.0375 mol B) 0.300 mol C) 0.150 mol D) 0.600 mol E) 0.0750 mol 11. How many moles of carbon monoxide gas are produced from the reaction of 5.00 moles of SnO2(s) with 8.00 moles of carbon according to the equation below? SnO2(s) + 2C(s) ® Sn(s) + 2CO(g) A) 10.0 mol B) 16.0 mol C) 5.00 mol D) 4.00 mol E) 8.00 mol 12. A) B) C) D) E) How many mL of 0.200 M HCl(aq) are neutralized by 5.00 g of Mg(OH)2(s)? 21.4 mL 2330 mL 857 mL 429 mL 1710 mL 13. A 20.0-mL sample of sulfuric acid from a lake near a mine was titrated to the stoichiometric point with 9.92 mL of 0.0120 M NaOH(aq). What is the molarity of sulfuric acid in the sample? A) 0.00238 M B) 0.00398 M C) 0.00595 M D) 0.00298 M E) 0.0119 M 14. Calculate the volume of carbon dioxide produced at STP by the combustion of 227 grams of propane, C3H8(g). A) 462 L B) 0.690 L C) 0.920 L D) 116 L E) 346 L 15. Consider the following reaction. CS2(g) + 3O2(g) ® CO2(g) + 2SO2(g) If 2.50 moles of CS2(g) are burned, what volume of SO2(g) is produced at STP? A) 112 L B) 56.0 L C) 5.00 L D) 22.4 L E) 28.0 L 16. A) B) C) D) E) Calculate the volume occupied by 12.4 g of nitrogen gas at STP. 4.96 L 10.9 L 22.4 L 19.8 L 9.92 L 17. A) B) C) D) E) Calculate the volume occupied by 5.75 moles of chlorine gas at STP. 258 L 141 L 129 L 64.4 L 22.4 L 18. If the standard enthalpy of formation of N2O(g) is +82.05 kJ · mol–1, calculate the reaction enthalpy for 2N2O(g) ® 2N2(g) + O2(g) A) +82.05 kJ B) –82.05 kJ C) –41.03 kJ D) –164.10 kJ E) +164.10 kJ 19. The standard enthalpies of combustion of CH3OH(l), C(s), and hydrogen gas are –726, – 394, and –286 kJ · mol–1, respectively. What is the standard enthalpy of formation of CH3OH(l)? A) –620 kJ · mol–1 B) –240 kJ · mol–1 C) –484 kJ · mol–1 D) +620 kJ · mol–1 E) –240 kJ · mol–1 20. Consider the heating curve for one mole of a substance that melts at –23oC and boils at 327 oC. A) B) C) D) E) If the heat is added at a constant rate of 180 J/min, the molar enthalpy of vaporization of the substance is +1.5 kJ · mol–1 +0.24 kJ · mol–1 +0.60 kJ · mol–1 +2.7 · mol–1 +3.0 kJ · mol–1 21. The standard enthalpy of combustion of octane, C8H18(l), is –5471 kJ · mol–1. The standard enthalpies of formation of H2O(l) and CO2(g) are –285.83 and –393.51 kJ · mol– 1, respectively. What is the standard enthalpy of formation of octane? A) –689 kJ · mol–1 B) +250 kJ · mol–1 C) –438 kJ · mol–1 D) +689 kJ · mol–1 E) –250 kJ · mol–1 Short-answer Questions (4 marks each) 22. Fill in the blanks and the correct symbol for "E" in the following table. Symbol = E E 75E (Z = 33) E Atomic Number 24 ___ 38 Number of Electrons 24 ___ 38 Number of Neutrons 28 ___ 49 23. Complete and balance the equations for any reactions which will occur for the following situations. Write the net ionic equation where appropriate. a) BaSO4(s) + NaCl(aq) ® b) Pb(NO3)2(aq) + Na2CrO4(aq) ® c) Ca(OH)2(aq) + H2SO4(aq) ® 24. If 3.00 moles of sulfur dioxide occupy 4.00 L at 120oC, calculate the pressure using both the van der Waals and ideal gas equations. The van der Waals constants for sulfur dioxide are a = 6.87 L2 atm mol–2 and b = 0.0568 L mol–1. Explain the results. 25. If the standard enthalpy of combustion of acetylene, C2H2(g), is –1300 kJ · mol–1, how many liters of acetylene measured at 25oC and 2.62 atm must be burned to liberate 10.0 × 106 kJ of heat? Long-answer Questions (6 marks each) 26. The following elemental analysis was found for artificial sweetener aspartame (commercially sold as NutraSweetTM): C, 57.1; H, 6.1; N, 9.5; and O 27.2% by mass What is the empiracal formula of aspartame? 27. Cobalt(II)chloride exists as a hydrated salt that can be represented by the formula CoCl2 . xH2O. In an experiment to determine the exact formula of this hydrated salt, 1.024 g of the hydrate was dissolved in 250 mL of water and excess sodium hydroxide was added to the resulting solution. The reaction that occured produced 0.573 g of cobalt(II)hydroxide. Determine the formula of hydrated cobalt(II)hydroxide (i.e. the value of x in CoCl2 . xH2O) 28. A 2.032 g sample of menthol (C10H20O) is introduced into a bomb calorimeter and completely burned with oxygen. The heat of combustion was found to be -6310 kJ/mol. The temperature of the calorimeter increases from 22.37 to 36.52 oC. Calculate the heat capacity of the calorimeter: *** END OF EXAMINIATION *** Mid-term Examination Chemistry 217 Answer Key 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. D B A A A E C A B C E C D E A E C D E A E 33, 33, 42 a) BaSO4(s) + NaCl(aq) ® No reaction b) Pb(NO3)2 (aq) + Na2CrO4 (aq) ® PbCrO4 (s) + 2NaNO3 (aq) Net: Pb2+ (aq) + CrO42- (aq) ® PbCrO4 (s) c) Ca(OH)2 (aq) + H2SO4 (aq) ® Ca SO4 (s) + 2H2O (l) Net: Ca2+ (aq) + SO42- (aq) ® Ca SO4 (s) 24.Ideal gas: 24.2 atm and VDW gas: 21.4 atm Only at low pressures will VDW gas approximte an ideal gas. 25. 7.2 ´ 104 L 26. C H N O (57.1)/(12) (6.1)/(1) (9.5)/(14) (27.2)/(16) = = = = (Wt/MWt) Divide by .67857 Best Ratio 4.7583 6.1 .67857 1.70 7.01 8.99 1 2.5 14 18 2 5 C14H18N2O5 27. 0.573 g of Co(OH)2 ===> 6.16 x 10-3 moles Moles of CoCl2 . xH2O = Moles of Co(OH)2 MWt (CoCl2 . xH2O) = (1.024 g)/(6.16 x 10-3 moles) = 166.2 g/mol CoCl2 . xH2O = 166.2 xH2O = 36.2 x = 36.2/18 = 2 CoCl2 . 2H2O 28. 2.032 g ==> 1.302 x 10-2 mol menthol (-6310 kJ/mol)(1.302 x 10-2 mol) = -82.19 kJ q = -C x DT -82.19 kJ = -C(36.52 - 22.37 oC) C = (-82.19 kJ)/(14.15 oC) = 5.81 kJ/oC or 5.81 kJ/K
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