Practice Exam #4 with Answers
Transcription
Practice Exam #4 with Answers
CH1410 Practice Exam #4 Multiple Choice - Write the letter of the BEST CHOICE in the space provided. (YOU MUST INCLUDE A SOLUTION PLAN. NO CREDIT WILL BE AWARDED FOR SIMPLY CHOOSING THE CORRECT ANSWER FOR PROBLEMS WHICH INCLUDE A CALCULATION. (#’s 7-13, 15, 16, 21-26)) D _____ 1. Consider the following n-alkanes: CH4, C2H6, C3H8, C4H10 Which of these would you expect to have the highest boiling point? A) CH4 B) C2H6 C) C3H8 D) C4H10 A _____ 2. Two compounds are considered as isomers if they have the D A) same molecular formula AND different structure. B) same molecular formula AND same structure. C) different molecular formula AND different structure. D) different molecular formula AND same structure. _____ 3. Name the following alkene: A) 2-propyl-2-isobutene B) 1-propyl-2-butene C) 1,1,3-trimethyl-1-pentene D) 3,4-dimethyl-2-pentene CH3 CH3 C C H CH3 CH CH3 B _____ 4. The combustion of alkanes, alkenes and alkynes produces: A) water and carbon. B) carbon dioxide and water. C) carbon dioxide and hydrogen. D) hydrogen and water. _____ 5. Name the major functional group in the molecule pictured at right B A) alcohol B) ester C) carboxylic acid D) ketone O C H3C CH3 O C _____ 6. Name the following alkane: A) 2-ethyl-1,3-dimethyl propane B) 3,3-dimethyl pentane C) 3-ethyl pentane D) isoheptane CH3 CH2 CH CH2 CH2 CH3 CH3 A 7. We dissolve 2.45 g of sugar in 200.0 g water. What is the mass percent of sugar in the solution? _____ A) 1.21% B) 1.23% C) 2.42% D) 123% [(2.45)/(2.45+200.0)] x 100%= 1.21% D _____ 8. What is the mass percent of a sodium fluoride solution prepared by dissolving 0.64 moles of sodium fluoride (molar mass = 41.99 g/mole) in 63.5 grams of water? A) 26.9% B) 42.3% C) 70.3% D) 29.7% 0.64 x 41.99 = 26.87 g NaF [(26.87)/(26.87+63.5)] x 100% =29.7% D _____ 9.What is the molarity of a solution prepared by dissolving 10.7 g NaI (molar mass = 149.89 g/mole)in water to give 0.250 L of solution? A) 42.8 B) 0.0714 -4 C) 2.86x 10 D) 0.286 10.7/149.89= 0.0714 mol NaI 0.0714 mol NaI/0.250 L = 0.286 M A _____10. How many grams of LiF would be present in 575 mL of 0.750 M LiF (molar mass = 25.94 g/mole) solution?? A) 11.2 B) 0.0338 C) 1.12 × 104 D) 19.9 (0.575 L) x(0.750 mol/L) x (25.94 g/mol)= 11.2 g LiF D _____ 11. What is the final concentration of a solution prepared by diluting 35.0 mL of 12.0 M HCl to a final volume of 1.20 L? A) 0.504 M M1 x V1 = M2 x V2 (12.0) x (0.035) = M1 x (1.20 L) B) 3.50 M C) 0.420 M D) 0.350 M M2 = 0.350 M B _____ 12. If you add 4.00 mL of pure water to 6.00 mL of 0.750 M NaCl solution, what is the concentration of sodium chloride in the diluted solution? A) 0.250 M B) 0.450 M C) 0.500 M D) 1.13 M (0.750) x (0.006) = M2 x (0.0100) M2 = 0.450 M A _____13. How many mL of 0.218 M sodium sulfate react with exactly 25.34 mL of 0.113 M BaCl2 given the reaction: BaCl2 (aq) + Na2SO4(aq) → BaSO4 (s) + 2NaCl (aq) A) 13.1 B) 5.52 C) 24.6 D) 2.86 D 0.02534 L BaCl2 solution X 0.113 mol BaCl2 1.00 L BaCl2 1.00 L Na2SO4 solution 0.218 mol Na2SO4 X X 1.00 mol Na2SO4 1.00 mol BaCl2 1000 ml 1.00 L _____14. In the following reaction, label the conjugate acid/base pairs and choose A,B,C, or D. NH4+ (aq) + H2O (aq) → NH3 (aq) + H3O+ (aq) A) NH4+ is an acid and H2O is its conjugate base. B) H2O is a base and NH3 is its conjugate acid. C) NH4+ is an acid and H3O+ is its conjugate base. D) H2O is a base and H3O+ is its conjugate acid. mass % = (mass of solute/mass of solution)x100 Molarity = mol/L = M X = 13.1 mL A _____15. A 25.0 ml sample of 0.105 M HCl was titrated to an endpoint with 31.5 ml of NaOH. What is the concentration of the NaOH? A) 0.0833 M B) 0.132 M C) 0.105 M D) 0.075 M D ______16.Exactly 17.0 mL of a H2SO4 solution was required to neutralize 45.0 mL of 0.235 M NaOH. What was the concentration of the H2SO4 solution? H2SO4 (aq) + 2NaOH (aq) → 2H2O (l) + Na2SO4 (aq) A) 5.63 M B) 0.622 M C) 0.00529 M D) 0.311 M D _____17. Which of the following acids is a diprotic, weak acid? A) sulfuric acid (H2SO4) C) hydrobromic acid (HBr) B) phosphoric acid (H3PO4) D) carbonic acid (H2CO3) A _____18. What is the concentration of the hydroxide ion given that the concentration of the hydronium ion is 1.5 × 10-5 M? A) 6.7 × 10-10 M B) 1.5 × 109 M C) 1.0 × 10-14 M D) 1.0 × 10-19 M ([OH-]) x (1.5 x 10-5) = 1.0 x 10-14 [OH-] = 6.7 x 10-10 A _____19. What is the pH of a solution that has a H⁺ concentration equal to 1.76 × 10-5 M? A) 4.75 C) 0.22 B) 5.20 D) 10.20 pH = -log(1.76 x10-5 ) = 4.75 C _____20. What is the [H⁺] in a solution that has a pH of 3.35? A) 1 × 103.35 M B) 2.2 × 103 M C) 4.5 × 10-4 M D) 3.35 × 10-14 M [H+} = 10-pH = 10-3.35 = 4.5 x 10-4 C _____21. Convert 1.50 atm to torr. A) 760 torr C) 1140 torr B) 875 torr D) 1000 torr C _____22. The volume of a gas is proportional to the temperature of a gas is known as A) Avogadro's Law C) Charles's Law B) Ideal Gas Law D) Boyle's Law B _____23. A balloon filled with 0.500 L of air at sea level is submerged in the water to a depth that produces a pressure of 3.25 atm. What is the volume of the balloon at this depth? (P1) (V1)= (P2) (V2) A) 1.63 L B) 0.154 L C) 6.50 L D)0.615 L Molarity = mol/L = M (1) (0.500)= (3.25) (V2) pH = -log[H3O+] [H3O+] = 10-pH [H3O+][OH-] = Kw = 1x10-14 C _____24. A gas sample occupies 3.50 liters of volume at 20.°C. What volume will this gas occupy at 100.°C (reported to three significant figures)? D (V1)/ (T1)= (V2) /(T2) A) 0.224 L B) 2.75 L C) 4.46 L D) 17.5 L (3.50)/ (293)= (V2)/ (372) _____25. A balloon originally had a volume of 0.439 L at 44°C and a pressure of 729 torr. To what temperature must the balloon be cooled to reduce its volume to 378 mL if the pressure remained constant? A) 0°C B) 38°C C) 95°C D) 273°C (V1)/ (T1)= (V2) /(T2) (0.439)/ (317)= (0.378)/ (T2) B _____26. A sample of helium gas initially at 37.0°C, 785 torr and 2.00 L was heated to 58.0°C while the volume expanded to 3.24 L. What is the final pressure in atm? A) 517 B) 0.679 C) 1.79 D)3.21 (P1)(V1)/ (T1)= (P2)(V2) /(T2) 785/760 = 1.03 atm (1.03)(2.00)/ (310)= (P2)(3.24)/(331) A _____27. A sample of 0.255 mole of gas has a volume of 748 mL at 28°C. Calculate the pressure of this gas. (R= 0.0821 atm · L / mol · K) A) 8.42 atm B) 0.784 atm C) 0.00842 atm D) 7.84 × 10-4 atm (P)(V)= (n)(R)(T) (P)(0.748 L)= (0.255)(0.0821)(301) A _____28. What is the temperature (°C) of 2.48 moles of gas stored in a 30.0 L container at 1559 mm Hg? (R= 0.0821 L atm/ mol K) A) 302 B) 189 C) 29 D)-84 (P)(V)= (n)(R)(T) 1559/760 = 2.05 atm (2.05 atm)(30.0 L)= (2.48 L)(0.0821)(T) A _____29. How many liters of oxygen are needed to exactly react with 1.24 moles of methane at STP? CH4(g) + 2 O2(g) → CO2(g) + 2 H2O(g) A) 13.9 L B) 27.8 L C) 55.5 L D) 60.5 L 1.24 mol x 22.4 L = 27.8 L O2 1/2 x 27.8 L = 13.9 L CH4 C _____30. When 14.0 g of zinc metal (atomic weight = 65.39) reacts with excess HCl, how many liters of H2 gas are produced at STP? Zn(s) + 2 HCl(aq) → H2(g) + ZnCl2 (aq) A) 0.208 L B) 0.416 L 22.4 L H2 = 4.80 14.0 g Zn X 1.00 mol Zn X 1.00 mol H2 X C) 4.80 L 1.00 mol H2 1.00 mol Zn 65.39 g Zn D) 9.60 L P1V1=P2V2 V1/T1=V2/T2 P1/T1=P2/T2 Molar gas volume=22.4 L/mol at STP PV=nRT L H2 (R=0.0821 L-atm/mol-K)