CHEMISTRY Practice Exam #2 -Answers (KATZ)

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1 HEMISTRY Practice Exam #2 -Answers (KATZ) Section 1 - This section of the exam is multiple choice. hoose the EST 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. What is the correct name for Mnr 2. 2H 2 O? A. manganese bromide hydrate. cobalt dichloride dihydrate. manganese (I) bromide dihydrate. manganese (II) bromide dihydrate 2. What is the name of the acid formed when Hr gas is dissolved in water? A. bromic acid. bromous acid. hydrobromic acid. hydrobromous acid 3. Which one of the following combinations of names and formulas is incorrect? A. H 3 PO 4< > phosphoric acid. N 2 O 5 < >dinitrogen pentaoxide. NaHO 3 < >sodium carbonate. H 2 O 3< > carbonic acid 4. Which of the following solutions will have the highest concentration of chloride ions? A M Nal M Mgl M All M al2 5. How many milliliters of a 9.0 M H2SO4 solution are needed to make 0.35 L of a 3.5 M solution? A ml ml. 140 ml. 900 ml 6. Identify Hl. A) strong electrolyte, weak acid ) weak electrolyte, weak acid ) strong electrolyte, strong acid ) weak electrolyte, strong acid

2 7. Which of the following pairs of aqueous solutions will form a precipitate when mixed? A) NH4NO3 + Li2O3 ) Hg2(NO3)2 + LiI ) Nal + Li3PO4 ) Ag2H3O2 + u(no3)2 8. Identify the spectator ions in the following molecular equation. Kr(aq) + AgNO3(aq) Agr(s) + KNO3(aq) A) Ag+ and r- ) K+ and NO3 - ) K+ and r- ) Ag+ and NO3-9. 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 ) 0.40 M ) 0.10 M ) 0.36 M 10. Which of the following is an acid base reaction? A) (s) + O2(g) O2(g) ) 2 HlO4(aq) + a(oh)2(aq) 2 H2O(l) + a(lo4)2(aq) ) Fe(s) + 2 AgNO3(aq) 2 Ag(s) + Fe(NO3)2(aq) ) MgSO4(aq) + a(no3)2(aq) Mg(NO3)2(aq) + aso4(s) 11. etermine the oxidation state of Sn in Sn(SO4)2. A) +2 ) +4 ) +6 ) 0 A 12. What element is undergoing oxidation in the following reaction? Zn(s) + 2 AgNO3(aq) Zn(NO3)2(aq) + 2 Ag(s) A) Zn ) N ) O ) Ag 13. To what temperature must a balloon, initially at 25 and 2.00 L, be heated in order to have a volume of 6.00 L? A) 993 K ) 403 K ) 75 K ) 894 K

3 A 14. How many moles of O are contained in a 5.00 L tank at 155 and 2.80 atm? A) moles ) 1.10 moles ) 2.51 moles ) moles 15. What is the volume of 5.60 g of O2 at 7.78 atm and 415K? A) 1.53 L ) 565 L ) 24.5 L ) L 16. Which of the following samples will have the greatest volume at STP? A) 22 g O ) 22 g He ) 22 g O2 ) 22 g l2 17. Place the following gases in order of increasing density at STP. N2 NH3 N2O4 Ar A) N2O4 < Ar < N2 < NH3 ) Ar < N2O4 < N2 < NH3 ) NH3 < Ar < N2 < N2O4 ) NH3 < N2 < Ar < N2O4 18. The density of a gas is 1.43 g/l at STP. What is the gas? A) l2 ) S ) O2 ) Ne 19. A 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 ) 33.9 g/mol ) 12.2 g/mol ) 38.0 g/mol 20. A mixture of He, Ne and Ar has a pressure of 7.85 atm. If the Ne has a mole fraction of 0.47 and Ar has a mole fraction of 0.23, what is the pressure of He? A) 4.2 atm ) 3.7 atm ) 1.8 atm ) 2.4 atm

4 21. Which statement is TRUE about kinetic molecular theory? A A) A single particle does not move in a straight line. ) The size of the particle is large compared to the volume. ) The collisions of particles with one another are completely elastic. ) The average kinetic energy of a particle is not proportional to the temperature 22. Which of the following signs on q and w represent a system that is doing work on the surroundings, as well as gaining heat from the surroundings? A) q = +, w = - ) q = -, w = + ) q = +, w = + ) q = -, w = alculate the change internal energy (ΔE) for a system that is giving off 45.0 kj of heat and is performing 855 J of work on the surroundings. A) 44.1 kj ) kj ) kj ) 9.00 x 102 kj A 24. A sample of copper absorbs 43.6 kj of heat, resulting in a temperature rise of 75.0, determine the mass (in kg) of the copper sample if the specific heat capacity of copper is J/g. A) 1.51 kg ) 6.62 kg ) 1.26 kg ) 7.94 kg 25. The specific heat capacity of liquid water is 4.18 J/g-K. How many joules of heat are needed to raise the temperature of 5.00 g of water from 25.1 to 65.3? A) 48.1 J ) 840 J ) J ) J 26. Which of the following substances (with specific heat capacity provided) would show the greatest temperature change upon absorbing J of heat? A) 10.0 g Fe, Fe = J/g ) 10.0 g H2O, H2O = 4.18 J/g ) 10.0 g ethanol, ethanol = 2.42 J/g ) 10.0 g Au, Au = J/g

5 27. How much energy is evolved during the reaction of 48.7 g of Al, according to the reaction below? Assume that there is excess Fe2O3. Fe2O3(s) + 2 Al(s) Al2O3(s) + 2 Fe(s) ΔH rxn = -852 kj A) 415 kj ) 769 kj ) 241 kj ) 130 kj 28. Use the standard reaction enthalpies given below to determine ΔH rxn for the following reaction: 2 NO(g) + O2(g) 2 NO2(g) ΔH rxn =? Given: N2(g) + O2(g) 2 NO(g) ΔH rxn = +183 kj 1/2 N2(g) + O2(g) NO2(g) ΔH rxn = +33 kj A) kj ) -117 kj ) -333 kj ) +115 kj 29. hoose the reaction that illustrates ΔH f for NaHO3. A) Na(s) + H2(g) + (s) + O2(g) NaHO3 (s) ) Na+(aq) + HO3-1 (aq) NaHO3 (s) ) Na+(aq) + H2O (l) + O2 (g) NaHO3 (s) ) Na(s) + 1/2 H2(g) + (s) + 3/2 O2(g) NaHO3 (s) 30. Use the information provided to determine ΔH rxn for the following reaction: ΔH f (kj/mol) H4(g) + 3 l2(g) Hl3(l) + 3 Hl(g) ΔH rxn =? H4(g) -75 Hl3(l) -134 Hl(g) -92 A) -151 kj ) -335 kj ) +662 kj ) +117 kj

6 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. ul2 (aq) + 2 NaOH (aq) u(oh)2 (s) + 2 Nal (aq) 2. Solid boron(iii) oxide reacts with hydrofluoric acid to yield boron trifluoride gas and water. 2O3 (s) + 6 HF (aq) 2 F3 (g) + 3 H2O 3. Liquid benzene ( 6 H 6 ) reacts with oxygen gas to yield carbon dioxide and water. 2 6H6 (l) + 15 O2 (g) 12 O2 (g) + 6 H2O (g) Section 3 - alculations involving Solutions 1. alculate the molarity of a solution prepared by dissolving 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) = mol LiOH ( mol LiOH)/(0.750 L) = M 2. escribe how to prepare ml of M Nal (MM = g/mol) from solid Nal. (.2500 L soln) x (3.000 mol/1.000 L soln) x (58.45 g Nal/1 mol Nal) = g Nal g Nal is dissolved in enough water to make ml.

7 Section 4 - alculations Involving hemical Equations onsider the following reaction al 2 (s) + H 2 SO 4 (l) > aso 4 (s) + 2 Hl (g) A mixture of 2.65 g of al 2 and 6.78 g of H 2 SO 4 are allowed to react. Molar masses: al 2, H 2 SO 4, aso 4, Hl, How many grams of aso 4 could theoretically be produced from the 2.65 g of al 2? Answer: g 2. How many grams of aso 4 could theoretically be produced from 6.78 g of H 2 SO 4? Which is the limiting reagent in this reaction? 16.1 Answer: g al2 Answer: 4. If 1.25 g of aso 4 is actually isolated, what is the percentage yield for the reaction? 42.1% Answer:

8 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. The barometric pressure is 753 torr. If the mass of the liquid retained in the flask is g, what is its molar mass? a. Find the number of moles of gas present using the ideal gas law. PV = nrt; n= (PV)/(RT) = (753/760)(.273)/(.0821)(273+99) = (.991)(.273)/(.0821)(372) = mol b. Using the measured mass of the liquid, find its molar mass. molar mass = (1.365 g)/( mol) = 160. g/mole 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 and 753 torr. from the reaction. (Pwater = 24 torr at 25 ) 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 Hl (aq) Znl2 (aq) + H2 (g) b. orrecting for water vapor pressure, what was the pressure of the hydrogen gas collected? = 729 torr = 729/760 atm = atm c. Using the ideal gas equation, calculate the number of moles of hydrogen gas collected? n= (PV)/(RT) = (0.959)(.195)/(.0821)(298) = mol H2 d. How many grams of zinc were present in the original reaction? mol H2 X (1 mol Zn)/(1 mol H2 )X (65.4 g Zn)/(1.00 mol Zn) = g Zn

CHEMISTRY Practice Exam #2 (KATZ)

CHEMISTRY Practice Exam #2 (KATZ) 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