Homework 3 Student Chem1046 PDF

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Broward College, South Campus Homework 3 CHM 1046 Instructor: Prakash Manandhar, PhD Due date: July 8, 2019 (Before the class-in person) (Please submit your answer in scantron) Chapter Covered: 6 and 17 Textbook: Chemistry: A Molecular Approach by Nivaldo J. Tro, 4th Edition;

Multiple-Choice Questions (50X0.5= 25 Points) 1. The internal energy of a system is always increased by ________. A) adding heat to the system B) having the system do work on the surroundings C) withdrawing heat from the system D) adding heat to the system and having the system do work on the surroundings E) a volume decompression 2. When a system ________, ΔE is always negative. A) absorbs heat and does work B) gives off heat and does work C) absorbs heat and has work done on it D) gives off heat and has work done on it E) None of the above is always negative. 3. The internal energy can be increased by ________. (a) transferring heat from the surroundings to the system (b) transferring heat from the system to the surroundings (c) doing work on the system A) a only B) b only C) c only D) a and c E) b and c 4. A ________ ΔH corresponds to an ________ process. A) negative, endothermic B) negative, exothermic C) positive, exothermic D) zero, exothermic E) zero, endothermic

5. For a given process at constant pressure, w is positive. This means that the process involves ________. A) work being done by the system on the surroundings B) work being done by the surroundings on the system C) no work being done D) an equal amount of work done on the system and by the system E) work being done against a vacuum 6. A chemical reaction that absorbs heat from the surroundings is said to be ________ and has a ________ ΔH at constant pressure. A) endothermic, positive B) endothermic, negative C) exothermic, negative D) exothermic, positive E) exothermic, neutral 7. The reaction 4Al (s) + 3O2 (g) → 2 Al2O3 (s) ΔH° = -3351 kJ is ________, and therefore heat is ________ by the reaction. A) endothermic, released B) endothermic, absorbed C) exothermic, released D) exothermic, absorbed E) thermoneutral, neither released nor absorbed 8. For which one of the following reactions is ΔH°rxn equal to the heat of formation of the product? A) N2 (g) + 3H2 (g) → 2NH3 (g) B) (1/2)N2 (g) + O2 (g) → NO2(g) C) 6C (s) + 6H (g) → C6H6 (l) D) P (g) + 4H (g) + Br (g) → PH4Br (l) E) 12C (g) + 11H2 (g) + 11O (g) → C6H22O11 (g) 9. Consider the following two reactions: A → 2B A→C

ΔH°rxn = 456.7 kJ/mol ΔH°rxn = -22.1 kJ/mol

Determine the enthalpy change for the process: 2B → C A) -478.8 kJ/mol B) -434.6 kJ/mol

C) 434.6 kJ/mol D) 478.8 kJ/mol E) More information is needed to solve the problem. 10. In the reaction below, ΔH°f is zero for ________. Ni (s) + 2CO (g) + 2PF3 (g) → Ni(CO)2(PF3)2 (l) A) Ni (s) B) CO (g) C) PF3 (g) D) Ni(CO)2(PF3)2 (l) E) both CO (g) and PF3 (g) 11. The change in the internal energy of a system that absorbs 2,500 J of heat and that does 7,655 J of work on the surroundings is ________ J. A) 10,155 B) 5,155 C) -5,155 D) -10,155 E) 1.91 × 107 12. Hydrogen gas and bromine gas react to form hydrogen bromide gas. How much heat (kJ) is released when 155 grams of HBr is formed in this reaction? ΔH° = -72 kJ. A) 137 B) 69 C) -69 D) -137 E) 1.12 × 105 13. The value of ΔH° for the reaction below is -790 kJ. The enthalpy change accompanying the reaction of 0.95 g of S is ________ kJ. 2S (s) + 3O2 (g) → 2SO3 (g) A) 23 B) -23 C) -12 D) 12 E) -790 14. Carbon monoxide and oxygen gas react to form carbon dioxide. How much heat is released when 89.5 grams of O2 (g) reacts with excess CO? ΔH° = -482 kJ. A) 1.35 × 103 kJ B) 2.70 × 103 kJ

C) 1.35 × 10-3 kJ D) 674 kJ E) 4.31 × 104 kJ 15. The value of ΔH° for the reaction below is +128.1 kJ: CH3OH (l) → CO (g) + 2H2 (g) How many kJ of heat are consumed when 5.10 g of CO (g) is formed as shown in the equation? A) 0.182 kJ B) 162 kJ C) 8.31 kJ D) 23.3 kJ E) 62.0 kJ 16. How many kJ of heat are released when 15.75 g of Ba (s) reacts completely with oxygen gas to form BaO (s)? ΔH° = -1107 kJ. A) 63.5 kJ B) 20.8 kJ C) 114 kJ D) 70.3 kJ E) 35.1 kJ 17. The molar heat capacity of an unknown substance is 92.1 J/mol-K. If the unknown has a molar mass of 118 g/mol, what is the specific heat (J/g-K) of this substance? A) 1.28 B) -92.1 C) 1.09 × 104 D) 0.781 E) 92.1 18. The specific heat of liquid bromine is 0.226 J/g-K. How much heat (J) is required to raise the temperature of 10.0 mL of bromine from 25.00 °C to 27.30 °C? The density of liquid bromine: 3.12 g/mL. A) 5.20 J B) 16.2 J C) 300 J D) 32.4 J E) 10.4 J 19. Given the following reactions Fe2O3 (s) + 3CO (s) → 2Fe (s) + 3CO2 (g) ΔH = -28.0 kJ 3Fe (s) + 4CO2(s) → 4CO (g) + Fe3O4(s) ΔH = +12.5 kJ

the enthalpy of the reaction of Fe2O3 with CO 3Fe2O3 (s) + CO (g) → CO2 (g) + 2Fe3O4 (s) is ________ kJ. A) -59.0 B) 40.5 C) -15.5 D) -109 E) +109 20. Given the following reactions N2 (g) + O2 (g) → 2NO (g) 2N2O (g) → O2 (g) + 2N2 (g) the enthalpy of reaction for 2N2O (g) → 2NO (g) + N2 (g)

ΔH = +180.7 kJ ΔH = -163.2 kJ

is ________ kJ. A) 145.7 B) 343.9 C) -343.9 D) 17.5 E) -145.7 21. Given the data in the table below, ΔH°rxn for the reaction Ca(OH)2 + 2H3AsO4 → Ca(H2AsO4)2 + 2H2O is ________ kJ.

A) -744.9 B) -4519 C) -4219 D) -130.4 E) -76.4 22. For the following reactions, the ΔH°rxn is NOT equal to ΔH°f for the product except for ________.

A) 2Ca (s) + O2 (g) → 2CaO (s) B) 3Mg (s) + N2 (g) → Mg3N2 (s) C) C2H2 (g) + H2 (g) → H4 (g) D) 2C (graphite) + O2 (g) → 2CO (g) E) C (diamond) + O2 (g) → CO2 (g) 23. For the following reactions, the ΔH°rxn is NOT equal to ΔH°f for the product except for ________. A) N2 (g) + O2 (g) → 2NO (g) B) 2H2 (g) + O2 (g) → 2H2O (l) C) 2H2 (g) + O2 (g) → 2H2O (g) D) 2C (s, graphite) + 2H2(g) → C2H4 (g) E) H2O (l) + 1/2 O2 (g) → H2O2 (l) 24. For the following reactions, the ΔH°rxn is NOT equal to ΔH°f for the product except for ________. A) H2O (l) + 1/2O2 (g) → H2O2 (l) B) N2 (g) + O2 (g) → 2NO (g) C) 2H2 (g) + O2 (g) → 2H2O (l) D) 2H2 (g) + O2 (g) → 2H2O (g) E) none of the above 25. For the following reactions, the ΔH°rxn is NOT equal to ΔH°f for the product except for ________. A) H2 (g) + 1/2 O2 (g) → H2O (l) B) H2 (g) + O2 (g) → H2O2 (l) C) 2C (s, graphite) + 2H2 (g) → C2H4 (g) D) 1/2 N2 (g) + O2 (g) → NO2 (g) E) all of the above 26. The specific heat of liquid bromine is 0.226 J/g-K. How much heat (J) is required to raise the temperature of 10.0 mL of bromine from 25.00 °C to 27.30 °C? The density of liquid bromine: 3.12 g/mL. A) 5.20 J B) 16.2 J C) 300 J D) 32.4 J E) 10.4 J 27. ΔH for the reaction IF5 (g) → IF3 (g) + F2 (g)

is ________ kJ, give the data below. IF (g) + F2 (g) → IF3 (g) ΔH = -390 kJ IF (g) + 2F2 (g) → IF5 (g) ΔH = -745 kJ A) +355 B) -1135 C) +1135 D) +35 E) -35 28. Given the following reactions N2 (g) + 2O2 (g) → 2NO2 (g) ΔH = 66.4 kJ 2NO (g) + O2 (g) → 2NO2 (g) ΔH = -114.2 kJ the enthalpy of the reaction of the nitrogen to produce nitric oxide N2 (g) + O2 (g) → 2NO (g) is ________ kJ. A) 180.6 B) -47.8 C) 47.8 D) 90.3 E) -180.6 29. The value of ΔH° for the reaction below is +128.1 kJ: CH3OH (l) → CO (g) + 2H2 (g) How many kJ of heat are consumed when 5.10 g of CO (g) is formed as shown in the equation? A) 0.182 kJ B) 162 kJ C) 8.31 kJ D) 23.3 kJ E) 62.0 kJ 30. CH3OH (l) decomposes into carbon monoxide and hydrogen gas in the presence of heat. How much heat is consumed when 5.75 g of CO (g) is formed? ΔH° = +128.1 kJ. A) 26.3 kJ B) 23.3 kJ C) 62.0 kJ D) 162 kJ E) 8.3 kJ 31. The value of ΔH° for the reaction below is -1107 kJ:

2Ba (s) + O2 (g) → 2BaO (s) How many kJ of heat are released when 5.75 g of Ba (s) reacts completely with oxygen to form A) 96.3 kJ B) 26.3 kJ C) 46.4 kJ D) 23.2 kJ E) 193 kJ 32. Decreasing the pH of blood will cause hemoglobin to release ________. A) CO2 B) N2 C) H2 D) O2 E) Fe

33. A 25.0 mL sample of a solution of an unknown compound is titrated with a 0.115 M NaOH solution. The titration curve above was obtained. The unknown compound is ________. A) a strong acid B) a strong base C) a weak acid D) a weak base E) neither an acid nor a base 34. A 50.0 mL sample of a solution of a monoprotic acid is titrated with a 0.115 M NaOH solution. The titration curve above was obtained. The concentration of the monoprotic acid is about ________ mol/L. A) 0.120 B) 25.0 C) 0.240 D) 0.0600 E) 0.100

35. A 25.0 mL sample of a solution of a monoprotic acid is titrated with a 0.115 M NaOH solution. The titration curve above was obtained. Which of the following indicators would be best for this titration? A) methyl red B) bromthymol blue C) thymol blue D) phenolpthalein E) bromocresol purple Consider the following table of

values.

36. Which compound listed below has the greatest molar solubility in water? A) CdCO3 B) Cd(OH)2 C) AgI D) CaF2 E) ZnCO3 37. Which compound listed below has the smallest molar solubility in water? A) ZnCO3 B) Cd(OH)2 C) CdCO3 D) AgI E) CaF2 38. The molar solubility of ________ is not affected by the pH of the solution.

A) Na3PO4 B) NaF C) KNO3 D) AlCl3 E) MnS 39. In which one of the following solutions is silver chloride the most soluble? A) 0.200 M HCl B) 0.750 M LiNO3 C) 0.0150 M NH3 D) 0.185 M KCl E) pure H2O 40. Which one of the following is not amphoteric? A) Al(OH)3 B) Ca(OH)2 C) Cr(OH)3 D) Zn(OH)2 E) Sn(OH)2 41. For which salt should the aqueous solubility be most sensitive to pH? A) MgCl2 B) Mg(NO3)2 C) MgF2 D) MgBr2 E) MgI2 42. Which one of the following is amphoteric? A) H2SO4 B) H2O2 C) CO2 D) H2O E) NaOH 43. Why does fluoride treatment render teeth more resistant to decay? A) Fluoride kills the bacteria in the mouth that make the acids that decay teeth. B) Fluoride stimulates production of tooth enamel to replace that lost to decay. C) Fluoride reduces saliva production, keeping teeth drier and thus reducing decay. D) Fluoride converts hydroxyapatite to fluoroapatite that is less reactive with acids. E) Fluoride dissolves plaque, reducing its decaying contact with teeth. 44. Which is the correct A) = [Pb2+] [Cl–]2

expression for PbCl2 (s) dissolving in water?

B) C) D) E)

= [Pb2+] [Cl–] = [Pb2+]2 [Cl–] = [PbCl+] [Cl–] = [Pb+] [Cl2–]2

45. A 25.0-mL sample of 0.150 M hypochlorous acid is titrated with a 0.150 M NaOH solution. What is the pH after 13.3 mL of base is added? The of hypochlorous acid is 3.0 × 10-8. A) 7.25 B) 1.34 C) 4.43 D) 7.58 E) 7.46 46. A 25.0 mL sample of 0.723 M HCl concentration after the addition of A) 0.0181 B) 0.430 C) 0.723 D) 0.273 E) none of the above

is titrated with a KOH solution. The of KOH is ________ M.

47. A 25.0 mL sample of an acetic acid solution is titrated with a 0.175 M NaOH solution. The equivalence point is reached when 10.2 mL of the base is added. The concentration of acetic acid in the sample was ________ M. A) 0.365 B) 0.175 C) 0.119 D) 0.0714 E) none of the above

48. What is the pH of a solution which is prepared by mixing 55.0 mL of 0.183 M KOH and 10.0 mL of HC2H3O2? A) 13.122 B) 9.97 C) 7.74 D) 0.878 E) none of the above 49. What is the molar solubility of calcium carbonate ( CaCO3 ) in water? The solubilityproduct constant for CaCO3 is 4.5 × 10-9 at 25 °C. A) 2.3 × 10-9

B) 9.0 × 10-9 C) 8.35 D) 9.5 × 10-5 E) 6.7 × 10-5 50. What is the molar solubility of silver carbonate ( Ag2CO3 ) in water? The Ksp for Ag2CO3 is 8.1 × 10-12 at A) 1.3 × 10-4 B) 1.4 × 10-6 C) 2.0 × 10-4 D) 4.0 × 10-6 E) 2.7 × 10-12 51. In which aqueous system is A) O

least soluble?

B) 0.5 M HF C) 0.2 M HF D) 1.0 M HN E) 0.8 M KF 52. A result of the common-ion effect is ________. A) that some ions, such as Na+ (aq), frequently appear in solutions but do not participate in solubility equilibria B) that common ions, such as Na+ (aq), don't affect equilibrium constants C) that the selective precipitation of a metal ion, such as Ag+, is promoted by the addition of an appropriate counterion (X-) that produces a compound (AgX) with a very low solubility D) that ions such as K+ and Na+ are common ions, so that their values in equilibrium constant expressions are always 1.00 E) that common ions precipitate all counter-ions...