CHM 2045 Exam 2 (Form Code A) March 04, 2008 Instructions: On your scantron sheet enter your name, UF ID number (start on the first space and leave the last space blank), Discussion Section No. and Form Code (see above). This exam consists of 25 multiple choice questions each worth 10.0 points for a total maximum of 250 pts. Keep your exam sheet (mark your answers on it and the scantron sheet). Turn in only the scantron. Any bubbling error will count as an incorrect response. Your name on the answer sheet states the assertion: I hereby pledge that I have neither given nor received unauthorized aid during this exam 1. What is the vacuum wavelength of light that has a frequency of 1.4990 x 1010 s-1 ? a) 2.0 m b) 2.0 dm c) 2.0 cm d) 2.0 nm e) 2.0 pm 2. The lowest frequency light that will produce the photoelectric effect is called the “threshold frequency”. The threshold frequency for platinum is 1.3x1015 s-1. What is the closest value to the energy of a photon of this radiation? a) 8.6x10-19 J b) 1.96x1048 J c) 5.1x10-49 J d) 518 kJ e) 2.3x10-7 J 3. What is the closest value to the vacuum wavelength of the light (in nm) emitted when the electron in a hydrogen atom drops from energy level n=6 to energy level n=4? a) 1094 nm b) 2625 nm c) 4558 nm d) 2.63 x 10 -7 nm e) 1459 nm 4. What is the closest value to the longest wavelength of light that can Ionize a Hydrogen atom in its n=3 level? (Choose the closest value) a) 9.75 x 106 nm b) 273.5 nm c) 136.8 nm d) 820.6 nm e) -102.6 nm 5. How many radial (spherical) nodes exist in a 4p orbital? a) 0 b) 1 c) 2 d) 3 e) 4 6. Which of the following sets of quantum numbers (n, l, ml, ms) refers to an electron in a 3d orbital? a) (3, 1, 0, +½) b) (3, 2, 2, +½) c) (3, 3, -2, +½) d) (3, 0, 2, +½) e) (3, 4, 3, +½) 7. Rank the following bonds in order of increasing ionic character: N – O, Ca – O, C – F, Br – Br, K – F a) Br – Br < N – O < C – F < Ca – O < K – F b) N – O < C – F < Ca – O < K – F < Br – Br c) C – F < Ca – O < K – F < N – O < Br – Br d) Br – Br < Ca – O < K – F < C – F < N – O e) Br – Br < C – F < N – O < K – F < Ca – O 8. Arrange the following in order of increasing size: Ar, K+, Cl-, S2-, Ca2+ a) Ca2+ < K+ < Ar < Cl- < S2- b) Ar < K+ < Cl- < S2- < Ca2+ c) K+ < Ar < Cl- < S2- < Ca2+ c) Ar < K+ < Cl- < Ca2+ < S2- e) Ca2+ < K+ < Ar < S2- < Cl- 9. Identify the element having the ground-state electron configuration [Ar] 4s23d104p3. a) Ca b) Se c) P d) As e) V 10. Which is paramagnetic? a) Zn b) Zn+2 c) Ne d) Co e) Ca 11. Which of the following ground-state electron configurations corresponds to an atom that has the most negative value of the electron affinity? a) 1s22s22p63s1 b) 1s22s22p63s23p5 c) 1s22s22p63s23p2 d) 1s22s22p63s23p63d54s2 e)1s22s22p6 12. Rank the following ions in order of increasing ionization energy: O2–, Mg2+, F–, Na+. a) O2– < Mg2+ < F– < Na+ b) Mg2+ < O2– < Na+ < F– c) O2– < F– < Na+ < Mg2+ d) Mg2+ < Na+ < F– < O2– e) O2– < F– < Mg2+ < Na+ 13. Given the average bond dissociation enthalpies provided of the data sheet, estimate the closest value to the standard molar enthalpy of formation of ClF3 (gas). a) 765 kJ/mol b) -363 kJ/mol c) 147 kJ/mol d) -405 kJ/mol e) -810 kJ/mol 14. Given the average bond dissociation enthalpies on the data sheet: estimate the molar standard heat of reaction of the gas-phase reaction of hydrogen peroxide with methanol to yield formaldehyde and water, i.e. : HOOH (gas) + H3COH (gas) → H2CO (gas) + 2 H2O (gas) a) - 345 kJ/mol b) 96 kJ/mol c) -105 kJ/mol d) 4 kJ/mol e) +345 kJ/mol 15. In which of the following molecules would you expect the nitrogen-to-nitrogen bond to be the shortest? a) N2H4 b) N2 c) N2O4 d) NO2 e) all the same 16. Which of the following processes is endothermic? a) Cs+(g) + e– → Cs(g) b) F(g) + e– →F–(g) c) Cs+(g) + F–(g) → CsF(s) d) CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) e) ½F2(g) → F(g) 17. Which of the following requires a resonance hybrid for its Lewis structure? a) CO2 b) Cl2CO c) CO32- d) SF4 e) H2O 18. Predict the shape of BrF5. a) square pyramidal b) seesaw c) trigonal bipyramidal d) tetrahedral e) bent 19. What is the formal charge on N atom in the NO3- ion? a) +1 b) -1 c) +2 d) +3 e) 0 20. Predict the molecular shape of N2O. a) tetrahedral b) linear c) trigonal planar d) bent e) seesaw 21. Which of the following molecules would you expect to be polar? a) SF6 b) SF4 c) C2H4 d) BF3 e) XeF2 22. Which of the following molecules/ions has a central atom with a hybridization of sp3d2? a) SiF4 b) AsF6– c) BrF3 d) BF4– e) PF5 23. Which of the following molecular shapes is associated with sp3d hybridization? a) T-shaped b) square planar c) trigonal pyramidal d) bent e) octahedral 24. Which of the following molecules is nonpolar? a) ClF3 b) PF3 c) PF5 d) SF4 e) CH2F2 25. The nitrosyl ion, NO+, has ten bonding electrons and four antibonding electrons. Therefore, it has a bond order of a) 3 b) 6 c) 7 d) 14 e) 5 Fundamental Constants: h = 6.62608 x 10-34 Js RH = 2.180 x 10-18 J NA = 6.02214 x 1023 mol-1 c = 2.99792 x 108 m/s g = 9.80665 m/s2 R= 1.096776 x 107 m-1 See the Periodic Table, reverse of this page, for Atomic Weights in g/mol.