Chemistry 1411 Practice Exam 2, Chapters 5-8 Brown

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1 Chemistry 1411 Practice Exam 2, Chapters 5-8 Brown Some constants and equations: E = q + w q = C p T Heat = m T Cs h = X J. s c = X 10 8 m/s R H = 2.18 X J E = (2.18 X J)(1/n 2 i 1/n 2 f ) E = h = hc/ A periodic table is also attached to the end of the exam. 1. The first law of thermodynamics states a) All reactions are exothermic. b) All reactions produce work. c) The work done by a reaction equals the amount of heat it produces. d) Energy is not created or destroyed in any reaction. 2. When a reaction absorbs heat under constant pressure conditions, a) the heat = H and H will be negative. b) the heat = H and H will be positive. c) the heat = E and E will be positive. d) the heat = E and E will be negative. 3. H for the reaction 2N 2 (g) + 6H 2 (g) 4NH 3 (g) is kj. What is H for the reaction 2NH 3 (g) N 2 (g) + 3H 2 (g)? a) kj b) kj c) 92.4 kj d) kj 4. What is the E of a system that releases J of heat to the surroundings and does 18.2 J of work to the surroundings? a) J b) J c) J d) J 5. A 2.85 g sample of a food substance was burned in a calorimeter that had a heat capacity of 9.84 kj/ C. The temperature of the calorimeter increased from C to C. Calculate the amount of heat released per gram of the substance. a) kj/g b) kj/g c) kj/g d) kj/g

2 6. The specific heat of liquid mercury is 0.14 J/g C. How many joules of heat would be required to raise the temperature of 3.75 g of mercury from 25 C to 65 C? a) 19 J b) 25 J c) 16 J d) 21 J 7. A sample of aluminum metal at 75.0 C was placed in 100 ml of water at 24.0 C in a coffee cup calorimeter. The final temperature was 28.0 C. What was the mass of the aluminum? The specific heat of aluminum is J/g C and the specific heat of water is J/g C. a) 12.5 g b) 28.0 g c) 39.6 g d) 351 g 8. The combustion of ammonia with oxygen occurs by the reaction 4 NH 3 (g) + 7 O 2 (g) 4 NO 2 (g) + 6 H 2 O(g) H = 1132 kj Calculate the amount of heat released when 2.00 gram of NH 3 is combusted. (Hint: How many moles of NH 3 is this?) a) 33.2 kj b) 87.0 kj c) 11.4 kj d) 16.6 kj 9. From the following information, Substance H f (kj/mole) MgO(s) HCl(g) MgCl 2 (s) H 2 O(l) calculate H in kj for the following reaction: MgO(s) + 2 HCl(g) MgCl 2 (s) + H 2 O(l) a) +122 kj b) 122 kj c) +141 kj d) 141 kj 10. What is the wavelength of light that has a frequency of 1.20 X s 1? a) 2.50 X 10 7 m b) 1.20 X 10 8 m c) 25.0 cm d) 3.60 X 10 4 m

3 11. Which type of electromagnetic radiation has the highest energy? a) UV b) radio c) visible d) gamma 12. What is the wavelength of a photon with an energy of 5.25 X J? a) 3.78 X 10 7 m b) 2.64 X 10 6 m c) 2.38 X m d) 4.21 X m 13. Calculate the energy change associated with an electron transition from n=1 to n=6 in a hydrogen atom. a) 2.12 X J b) 5.52 X J c) 1.89 X J d) 4.60 X J 14. The values of the principal quantum number (n) and the secondary quantum number (l) of an electron in a 3p orbital are a) 2, 3 b) 3, 2 c) 3, 1 d) 2, Which set of quantum numbers cannot be correct? a) n = 1, l = 0, m l = 0 b) n = 3, l = 2, m l = 2 c) n = 3, l = 2, m l = 2 d) n = 5, l = 5, m l = The term degenerate orbitals indicates that the orbitals a) contain the maximum number of electrons b) have different principal quantum numbers c) have the same energy d) have different energies 17. Which diagram represents a violation of the Pauli exclusion principle? a) 1s 2s 2p 1s 2s 2p b) c) 1s 2s 2p 1s 2s 2p d) 18. Rank the following elements below in order of increasing atomic radius (smallest to largest): Mg, Na, P, Si, Ar a) Mg, Na, P, Si, Ar b) Ar, P, Si, Mg, Na c) Si, P, Ar, Na, Mg d) Na, Mg, Si, P, Ar

4 19. Which one of the following atoms has the largest effective nuclear charge, Z eff? a) C b) N c) O d) F 20. Which of the following elements has the highest ionization energy? a) Na b) Li c) Cl d) Ca 21. When a metal and a nonmetal react, which one tends to lose electrons? a) the metal b) the nonmetal c) either 22. Which one of the following ions has the largest radius? a) Na + b) Al 3+ c) P 3 d)f 23. Which will form an acidic solution when dissolved in water? a) Li 2 O b) Na 2 O c) CO 2 d) MgO 24. The best Lewis dot structure of the NO molecule has a) an unpaired electron on the nitrogen atom b) an unpaired electron on the oxygen atom c) a triple bond between N and O d) an expanded octet on N 25. The type of compound that is most likely to contain an ionic bond is a) one that is composed of a metal and a nonmetal b) a solid metal c) one that is composed of only nonmetals d) one that is nonpolar 26. Which compound has the lowest lattice energy? a) NaCl b) NaBr c) MgCl 2 d) MgBr The lattice energy of an ionic solid is greater if a) the ions have large sizes b) the charges of the ions are high c) the distance between the ions is large d) the distance between the ions is large and the charges are low 28. The PO 4 3 ion has how many total valence electrons? a) 24 b) 30 c) 32 d) 34 e) Of the molecules below, which is the most polar? a) HBr b) HF c) HCl d) HI 30. Which type of bond is the longest? a) single b) double c) triple d) all are the same

5 31. Given the electronegativities below, which of the following covalent single bonds is the least polar? Element: H C N O Electronegativity: a) O-H b) N-H c) C-H d) O-C e) C-N 32. What is the formal charge of the carbon atom in the carbon monoxide molecule? a) 0 b) +1 c) 1 d) +2 e) The Lewis electron-dot structure of PF 3 gives the central P atom a) 2 nonbonding pairs and 2 bonding pairs of electrons b) 1 nonbonding pair and 3 bonding pairs of electrons c) 3 nonbonding pairs and 1 bonding pair of electrons d) 2 nonbonding pairs and 3 bonding pairs of electrons 34. Which one of the following is the correct Lewis electron-dot formula of CO 3 2? a) b) c) d) 35. How many resonance forms can be drawn for the NO 3 ion? a) 0 b) 1 c) 2 d) Which of these violates the octet rule? a) SF 4 b) PCl 3 c) SiF 4 d) CS 2 End of Multiple-Choice Section

6 37. Write the electron configuration of nickel. Show the complete configuration, starting with the 1s orbital. Ni 38. Draw the orbital (box) diagram electron configuration for the element fluorine. Label the boxes. You may use the noble gas label for the inner electrons if you desire. F 39. Use reactions 1 and 2 to determine the value of H (in kj) for reaction 3. (1) N 2 (g) + 2O 2 (g) 2NO 2 (g) H = kj (2) NO(g) + 1/2 O 2 (g) NO 2 (g) H = 56.6 kj (3) N 2 (g) + O 2 (g) 2 NO(g) H =? 40. Using average bond energies, calculate H for the reaction C 2 H 4 (g) + 3 O 2 (g) > 2 CO 2 (g) + 2 H 2 O (g) Bond Dissociation Energies C=C 614 kj/mol C-H 413 kj/mol O=O 495 kj/mol C=O 799 kj/mol O-H 463 kj/mol

7 Answers 1. D 11. D 21. A 31. C 2. B 12. A 22. C 32. C 3. B 13. A 23. C 33. B 4. D 14. C 24. A 34. A 5. C 15. D 25. A 35. D 6. D 16. C 26. B 36. A 7. C 17. A 27. B 8. A 18. B 28. C 9. D 19. D 29. B 10. A 20. C 30. A 37. 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 8 Can you give the configuration for the Ni 2+ ion? m l 1s 2s 2p type of orbital Can you give the four quantum numbers for each electron? kj kj