CHM1045 Exam 3 Chapters 5, 8, & 9

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1 1. Which of the following conditions will never result in a decrease in the internal energy of a system? CHM1045 Exam 3 Chapters 5, 8, & 9 a. System loses heat and does work on the surroundings. b. System gains heat and does work on the surroundings. c. System gains heat and has work done on it by the surroundings. d. System loses heat and has work done on it by the surroundings. e. None of these is ALWAYS true. 2. What is the hybridization of krypton in krypton difluoride? a. sp 2 b. sp 3 c. sp 3 d d. sp 3 d 2 e. sp 3 d 3 f. sp 3 d 4 g. None of the above 3. Which of these ionic solids would require the least amount of energy to convert one mole of the solid to its constituent ions in the gas phase? a. LiF b. MgS c. FrI d. AlN e. MgO f. TiC 4. Which of the following is the most polar bond? a. FF b. ClF c. BrF d. IF e. OF 5. In an endothermic reaction the reactants are in energy and have bond enthalpy than the products : a. lower, greater b. lower, less c. Greater, greater d. Greater, less e. Not enough information

2 6. In which one of the following species does the central atom violate the octet rule? a. PF 4 b. SiCl 4 c. NF 3 d. ICl 4 e. ClO 2 7. In a steel cylinder, ozone gas (O 3 ) decomposes to oxygen gas. The work done is: a. Positive b. Negative c. Zero d. Not enough information is given 8. Predict the actual bond angles in ClBr 5 using the VSEPR theory. a. All less than 90 b. Contains both 90 and 120 angles c. All between 90 and 120 d. Some less than 90, some between 90 and 120, and some greater than 120 e. All greater than As the number of electrons shared between two atoms increases, the bond length decreases: a. True b. False c. It depends 10. Carbon monoxide contains (A) 3 sigma bonds (B) 2 sigma bonds and 1 pi bond (C) 1 sigma bond and 2 pi bonds (D) 3 pi bonds 11. In which species is the central atom NOT surrounded by exactly 8 valence electrons? (A) BF 4 (B) NCl 3 (C) PCl 4 (D) SF 4

3 12. The enthalpy change of which reaction corresponds to H f for Na 2 CO 3 (s) at 298 K? (A) 2Na (s) C (s) 3/2O 2(g) Na 2 CO 3(s) (B) Na 2 O (s) CO 2(g) Na 2 CO 3(s) (C) 2Na (aq) CO 3 2 (aq) Na 2 CO 3(s) (D) 2Na (aq) 2OH (aq) CO 2(aq) Na 2 CO 3(s) H 2 O 13. What is the shape of the ClF 3 molecule? (A) trigonal planar (B) trigonal pyramidal (C) Tshaped (D) Tetrahedral 14. Which applies to any endothermic reaction? (A) H < 0 (B) H > 0 (C) H = 0 (D) U = Which species has the largest FAF bond angle where A is the central atom? (A) BF 3 (B) CF 4 (C) NF 3 (D) OF When a bomb calorimeter is used to determine the heat of reaction, which property of the system under investigation is most likely to remain constant? (A) number of molecules (B) pressure (C) temperature (D) volume

4 17. What is the hybridization of a central atom with one double bond, four single bonds and two lone pairs? (A) sp 3 (B) sp 6 (C) sp 3 d 3 (D) sp 3 d 2 f An ice cube at 0.00 C is placed in 200. g of distilled water at C. The final temperature after the ice is completely melted is 5.00 C. What is the mass of the ice cube? (A) 23.6 g H fus = 340 J g 1 1, S H2O = J g 1 C (B) 46.3 g (C) 50.0 g (D) 800. g 19. If the enthalpy of vaporization for H 2 O (l) is 44.0 kj/mol,what is ΔH for the following reaction if H 2 O (l) is formed instead of H 2 O (g)? C 2 H 6(g) 7.5O 2(g) 2CO 2(g) 3H 2 O (g) (A) kj (B) kj (C) kj (D) kj 20. The nitrite ion can be represented by how many resonance structures? (A) 1 (B) 2 (C) 3 (D) 4 ΔH = kj 21. Calculate the change in enthalpy, ΔH, for the combustion of 11.2 L of hydrogen gas, measured at 0 C and 1 atm pressure, to form H 2 O (g). ΔHf of H 2 O (g) = kj mol 1. (A) 60.5 kj (B) 121 kj (C) 484 kj (D) 2710 kj 22. Which substance has both covalent and ionic bonds? (A) NH 4 Br (s) (B) KI (s) (C) CH 2 Cl 2(l) (D) SiF 4(g) 23. Which molecule has the largest bond order? (A) Li 2 (B) Be 2 (C) B 2 (D) C 2

5 24. Given these reactions: A 2B ΔH = 40 kj B C ΔH = 50 kj 2C D ΔH = 20 kj Calculate ΔH for the reaction; D A 4C. (A) 100 kj (B) 60 kj (C) 40 kj (D) 80 kj 25. Which species have one or more atoms that violate the octet rule? I. NO II. SF 2 III. PF 4 (B) I only (C) III only (D) I and II only (E) II and III only 26. Use bond energies to calculate ΔH in kj for the reaction; N 2 2H 2 N 2 H 4 Bond Energies are: H H 436 kj mol 1 N H 389 kj mol 1 N N 159 kj mol 1 N=N 418 kj mol 1 N N 941 kj mol 1 (A) 425 kj (B) 98 kj (C) 98 kj (D) 425 kj 27. In which species is the carbonnitrogen bond the shortest? (A) CH 3 NH 2 (B) CH 2 NH (C) (CH 3 ) 4 N (D) CH 3 CN 28. The standard enthalpy of formation for ammonia gas is 46.1 kj mol 1. Calculate ΔH for the decomposition of ammonia into nitrogen and hydrogen at 298K and 1 atm. (A) 92.2 kj (B) 46.1 kj (C) 46.1 kj (D) 92.2 kj 29. How many valence electrons are in the pyrophosphate ion, P 2 O 7 4? (A) 48 (B) 52 (C) 54 (D) 56

6 30. What is the specific heat capacity of mercury (in J g 1 C 1 ) if a 25.0 g sample requires 19.3 J to raise its temperature from 24.5 C to 30.0 C? (A) (B) (C) 0.14 (D) In which species does the central atom have one or more lone pairs of valence electrons? (A) AlCl 4 (B) CO 2 (C) PCl 4 (D) SO Which of the following are exothermic processes? I. combustion of ethanol II. dehydration of calcium sulfate dihydrate (A) I only (B) II only (C) both I and II (D) neither I nor II 33. In which pair of formulas are both species polar? (A) CO 2 and H 2 O (B) BF 3 and PCl 3 (C) SO 2 and SCl 2 (D) CS 2 and NO Which has the largest dipole moment? (A) HF (g) (B) HCl (g) (C) HBr (g) (D) HI (g) 35. In which choice are the sodium halides listed in order of increasing lattice energy? (A) NaF, NaCl, NaBr (B) NaBr, NaCl, NaF (C) NaCl, NaF, NaBr (D) NaCl, NaBr, NaF

Form J. Test #4 Last Name First Name Zumdahl, Chapters 8 and 9 November 23, 2004

Form J. Test #4 Last Name First Name Zumdahl, Chapters 8 and 9 November 23, 2004 Form J Chemistry 1441-023 Name (please print) Test #4 Last Name First Name Zumdahl, Chapters 8 and 9 November 23, 2004 Instructions: 1. This exam consists of 27 questions. 2. No scratch paper is allowed.