Moorpark College Chemistry 11 Fall 2011 Instructor: Professor Gopal Examination #2: Section Two October 17, 2011 Name: (print) Directions: Make sure your examination contains ELEVEN total pages (including this cover sheet) when instructed to do so. Answer all the questions in the spaces provided. Be sure to show all your work for partial credit. NEGATIVE ION POSITIVE ION SOLUBILITY* Chloride (Cl - ), Bromide (Br - ), Ag +, Pb 2+, Cu + Insoluble Iodide (I - ) Phosphate (PO 3-4 ), Carbonate All positive ions EXCEPT Insoluble (CO 2-3 ), Sulfite (SO 2-3 ), Hydroxide (OH - ) + alkali ions and NH 4 Sulfate (SO 2-4 ) Ca 2+, Sr 2+, Ba 2+, Ra 2+, Ag +, Insoluble Pb 2+ Sulfide (S 2- ) All positive ions EXCEPT alkali ions, alkaline earth + ions, NH 4 Insoluble * NOTE: All nitrates, perchlorates, and acetates are soluble. Li > K > Ca > Na > Mg > Al > Mn > Zn > Cr > Fe > Cd > Ni > Sn > Pb > H 2 > Cu > Ag > Au Question 1. 27. (54 pts.) 28. (14 pts.) 29. (20 pts.) 30. (12 pts.) TOTAL (100 points) Points 1
Chemistry 11 Fall 2011 Examination #2 For the first portion of this exam, select the best answer choice for the questions below and mark the answers on your scantron. Then answer the free response questions that follow (100 pts. total; multiple choice 2 pts. each). 1. When the equation below is properly balanced, the number of moles of CO 2 will be: C 6 H 14 + O 2 CO 2 + H 2 O A. 6 moles B. 12 moles C. 1 moles D. 3 moles E. 9 moles 2. Which of the following is expected to be least soluble in water? A. HOCH 2 CH 2 OH B. CH 3 OH C. CH 3 CH 2 CH 2 CH 2 CH 3 D. MgCl 2 E. CH 3 COOH 3. What is the mass of 9.44 x 10 24 molecules of NO 2? A. 2.05 x 10 2 g B. 2.94 x 10 2 g C. 7.21 x 10 2 g D. 341 g E. 685 g 4. What is the weight of 0.300 moles of glucose, C 6 H 12 O 6? A. 9.00 g B. 27.0 g C. 54.0 g D. 108 g E. 1.67 x 10-3 g 2
5. Which of the following is NOT a strong base? A. NaOH B. LiOH C. K 2 O D. Be(OH) 2 E. All of the above are strong bases 6. Which of the following substances has London dispersion forces as its only intermolecular force? A. CH 3 OH B. NH 3 C. H 2 O D. CH 4 E. HCl 7. Which of the following pairs of compounds could create a suitable buffer system? A. Sodium sulfate and sodium hydroxide B. Ammonia and potassium hydroxide C. Sodium chloride and sodium hydroxide D. Sodium acetate and acetic acid Carbonic acid and sodium chloride 8. A 25.0 L container is filled with nitrogen gas at a pressure of 950.0 mm Hg. How many moles of nitrogen are present at -92 ºC? A. 2.10 moles B. 1598 moles C. 86.1 moles D. 1.04 moles E. 2.50 moles 9. Breathing is an example of which gas law? A. Avogadro's Law B. Boyle's Law C. Charles' Law D. Dalton's Law E. Gay-Lussac s Law 3
10. Evidence that a chemical reaction has taken place is indicated by: A. Heat B. Gas bubbles C. Formation of a precipitate D. All of the above, namely heat, gas bubbles, and formation of a precipitate E. Only gas bubbles and formation of a precipitate 11. A patient visits the ER with a blood pressure reading of 142/97. This person is in which stage? A. Normal and should continue to maintain a healthy lifestyle. B. Pre-hypertension and should adopt a healthy lifestyle. C. Stage 1 hypertension and should take medication. D. Stage 2 hypertension and should take more than one medication. E. At risk of cardiac arrest and should be immediately admitted into the hospital. 12. Concentrated stock solution of nitric acid (15.70 M) is purchased by stockroom personnel with the goal of setting up for multiple lab experiments requiring 1500. ml of 0.5000 M HNO 3 (aq). How much water must be added to the stock solution in order to produce the desired quantity for the lab experiments? A. 47,100 ml B. 45,600 ml C. 48 ml D. 1500 ml E. 1452 ml 13. The label on a bottle of vinegar says it contains 5.0% (w/v) of acetic acid. The bottle contains 240 ml of vinegar. How many grams of acetic acid are in the bottle? A. 12 g B. 1200 g C. 48 g D. 2.1 g E. 2400 g 4
14. Which of the following statements is TRUE? A. A liquid with a low vapor pressure at room temperature will probably have a low surface tension and a high boiling point. B. A liquid with a low vapor pressure at room temperature will probably have a high surface tension and a high boiling point. C. A liquid with a high vapor pressure at room temperature will probably have high intermolecular forces and a low boiling point. D. A liquid with a low vapor pressure at room temperature will probably have high intermolecular forces and a low boiling point. E. A liquid with a low vapor pressure at room temperature will probably have a low surface tension and a low boiling point. 15. Which pairs of liquids are NOT likely to be miscible? A. H 2 O and CH 3 OH B. H 2 O and C 6 H 6 C. C 6 H 14 and CCl 4 D. CCl 4 and C 5 H 12 OH E. H 2 O and 0.1 g of NaCl 16. Which of the following is NOT a characteristic of a strong electrolyte? A. Strong electrolytes are good conductors of electricity. B. HCl is an example of a strong electrolyte. C. Strong electrolytes do not dissociate completely in solution. D. NaOH is an example of a strong electrolyte. E. None of the above 17. A quantity of gas has a volume of 250.0 L at 17.0 ºC and 3.00 atm pressure. To what volume must the gas be increased for the gas to be under STP conditions? A. 78.4 L B. 88.5 L C. 706 L D. 771 L E. 797 L 18. Which of the molecules below would NOT form hydrogen bonds? A. CH 3 OH B. CH 3 OCH 3 C. CH 3 COOH D. NH 3 E. None of these would hydrogen bond. 5
19. Arrange the following in the order of increasing boiling points: A. RbF < CO 2 < CH 3 OH < CH 3 Br < CH 3 I B. CO 2 < CH 3 OH < CH 3 Br < CH 3 I < RbF C. CH 3 Br < CH 3 OH < RbF < CO 2 < CH 3 I D. RbF < CH 3 OH < CH 3 Br < CH 3 I < CO 2 E. CO 2 < CH 3 I < CH 3 Br < CH 3 OH < RbF 20. What is the balanced net ionic equation for the reaction of CaCl 2 and AgNO 3? A. CaCl 2 (aq) + 2AgNO 3 (aq) Ca(NO 3 ) 2(aq) + 2AgCl(s) B. Ca 2+ (aq) + 2Cl (aq) + 2Ag + (aq) + 2NO 3 (aq) Ca 2+ (aq) + 2NO 3 (aq) + 2AgCl(s) C. 2Ag + (aq) + 2Cl (aq) 2AgCl(s) D. Ag + (aq) + Cl (aq) AgCl(s) E. Ca 2+ (aq) + 2Cl (aq) + 2Ag + (aq) + 2NO 3 (aq) Ca 2+ (aq) + 2NO 3 (aq) + 2Ag + (aq) + 2Cl (aq) 21. The condition of alkalosis is described by which of the following conditions? A. The blood ph lies between 7.5 and 7.8. B. A patient may feel dizzy and agitated. C. This condition may be caused by fever and rapid breathing (hyperventilation). D. All of the above (A, B, and C) are correct. E. None of the above (A, B, and C) are correct. 22. End point is defined as A. The final measurement in a buret B. An indicator in volumetric analysis C. A point in a titration where ph indicator changes color D. Stoichiometric point in a titration experiment E. All of the above 23. A constant volume of oxygen gas, O 2, is heated from 120 ºC to 212 ºC. The final pressure is 20.3 atm. What is the initial pressure? A. 11.5 atm B. 16.4 atm C. 25.1 atm D. 35.9 atm E. 10.5 atm 6
24. If the concentration of H + in a solution is 10-3 M, what will the concentration of OH - be in the same solution at 25 C? A. 10-3 M B. 10-11 M C. 10 11 M D. 2 x 10-11 M E. 10-14 M 25. Which of the following does NOT correctly characterize the Kinetic Molecular Theory of gases? A. Gases are compressible. B. Gases assume the shape/volume of their container. C. Gases are in continuous, random motion. D. The average kinetic energy of gas molecules does not change with time as long as temperature remains constant. E. Attractive and repulsive forces between gas molecules cannot be ignored. 26. A solution has a poh of 9.1. What is its ph? A. -4.9 B. -7.1 C. 9.1 D. 4.9 E. -9.1 27. A certain wine contains 0.0100 M NaHSO 3 as a preservative. What weight of NaHSO 3 is in a 750 ml bottle of this wine? A. 0.39 g B. 0.75 g C. 0.78 g D. 1.5 g E. 0.80 g END OF MULTIPLE CHOICE 7
FREE RESPONSE! SHOW ALL WORK IN THE SPACE PROVIDED TO RECEIVE CREDIT! 28. (14 pts. total) When solutions of FeCl 3 and H 2 S react, the UNBALANCED molecular equation is 2FeCl 3 (aq) + 3H 2 S(aq) Fe 2 S 3 (s) + 6HCl(aq). A. (10 pts.) What is the mass of HCl produced when 90.0 g of FeCl 3 reacts with 52.0 g of H 2 S? What is the limiting reactant in this reaction? 90.0 g FeCl 3 x 1 mole FeCl 3 x 6 moles HCl x 36.461 g HCl = 60.7 g HCl 162.206 g FeCl 3 2 moles FeCl 3 1 mole HCl 52.0 g H 2 S x 1 mole H 2 S x 6 moles HCl x 36.461 g HCl = 111 g HCl 34.082 g H 2 S 3 moles H 2 S 1 mole HCl Mass of HCl produced is 60.7 g Limiting Reactant is FeCl 3 B. (4 pts.) If a student obtains 58.8 g of HCl in the laboratory, what is the percentage yield in the experiment? % yield = Actual yield = 58.8 g x 100 = 96.9% Theoretical yield 60.7 g 29. (20 pts. total; 4 pts. each) Write BALANCED equations (net ionic where appropriate) for each laboratory situation. Assume that solutions are aqueous unless otherwise indicated. Write NR if no reaction occurs. A. Solid silver is mixed with copper(ii) nitrate. No Reaction B. Aluminum chloride is reacted with calcium sulfate. No Reaction 8
C. Potassium metal is combined with hydrochloric acid. 2K (s) + 2HCl (aq) 2K (s) + 2H + (aq) H 2(g) + 2KCl (aq) H 2(g) + 2K + (aq) D. Aqueous solutions of lithium phosphate and barium nitrate are mixed together. 2Li 3 PO 4(aq) + 3Ba(NO 3 ) 2(aq) 3Ba 2+ (aq) + 2PO 4 3- (aq) 6LiNO 3(aq) + Ba 3 (PO 4 ) 2(s) Ba 3 (PO 4 ) 2(s) E. Combustion of liquid methanol (CH 3 OH) in air. 2CH 3 OH (l) + 3O 2(g) 2CO 2(g) + 4H 2 O (g) 30. (12 pts. total) ACIDS and BASES! A. (5 pts.) If 25.0 ml of a standard 0.05 M HCl solution is required to neutralize 20.0 ml of a solution of Sr(OH) 2, what is the concentration of the base? 2HCl (aq) + Sr(OH) 2(aq) SrCl 2(aq) + 2H 2 O (l) The number of moles of acid is twice the number of moles of base, therefore it will take twice as much base to neutralize the acid. moles acid = 2(moles base ) V A M A = 2V B M B 25.0 ml x 0.05 M = 2 x M B x 20.0 ml M B = 25.0 ml x 0.05 M = 0.03 M 2 x 20.0 ml 9
B. (7 pts.) What is a buffer solution? Give an example of an acid/base buffer system found in body fluids such as blood. If a body fluid contains excess hydrochloric acid, what is the condition called? How will the buffer in the body fluid help counteract the excess acid? You can use an equation to explain your answer or explain clearly in words. A buffer is a weak acid and its salt or conjugate base. A buffered solution resists changes in ph when either hydrogen ions or hydroxide ions are added to the solution. The most important buffer system in the body is carbonic acid/sodium bicarbonate buffer. Excess acid results in a condition called acidosis. The bicarbonate acts as the base and neutralizes the acid. HCl + NaHCO 3 NaCl + H 2 CO 3 (weak acid) The strong acid is neutralized by the sodium bicarbonate to give the weak acid. 10