Chemistry 105: General Chemistry I Dr. Gutow and Dr. Matsuno Spring 2004 Page 1

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1 Page 1 1) Name You are to keep this copy of the test. Your name is in case you leave it behind. 2) Use only a #2 pencil on the answer sheet. 3) Before starting the exam fill in your student ID# (not your SS#). Also fill in your name, course number and sign the form. 4) Fill in the test form section (A, B, C or D). Which form you have is shown in the upper right corner. 5) Do not begin the exam until you are told to. 6) You will not get your scan sheet back!!! Circle your answers on this exam sheet and then transfer them to the scan sheet when you are satisfied with all your answers. An answer key will be posted on the class web site and in the glass case across from the lab after the exam. 7) If atomic weights are needed use only those from the attached periodic table. 8) No scratch paper is to be used. Use the back of this exam sheet if necessary. 9) There are 40 equally weighted questions on this exam. You have 90 minutes to complete them. 10) If you believe there is more than one correct answer pick only the best answer. Useful Data Constants c = x 10 8 m/s h = 6.63 x Js density of H 2 O = 1.00 g/ml N A (Avogadro s #) =6.022 x particles mol -1 R (gas constant) = L atm mol -1 K -1 e (charge on electron) = 1.60 x C 1 D = x C m Units 2.54 cm = 1 inch 3.78 L = 1 gal 1 kg = 2.20 lb 1 % = 10,000 ppm 1 hr = 60 min 1 min = 60 seconds 1 amu = x kg molarity (M) = moles solute/l sol n molality (m)= moles solute/ kg solvent Equations % = fraction 100 % ppm = fraction 10 6 ppm T (in Kelvin) = T (in C) T (in Celsius) = (5/9) (T (in F) -32) π = imrt T b = imk b T f = imk f actual yield (g) % yield =100% # theoretical yield (g) F.C. = V.E - (# non-bonding e-) - 1/2(# of bonding e-) B.O. = 1/2 (bonding e- - antibonding e-) µ = Qr

2 Page 2 1. How many valence electrons does Al 3+ have? a. one b. two c. three d. six e. zero 2. How many valence electrons are contained in BrO -? a. 7 b. 6 c. 12 d. 13 e Indicate which of the following molecules contains a polar covalent bond a. O 2 b. N 2 c. CN d. H 2 e. Cl 2 4. How many shared electrons are there in the Lewis structure of CN -? a. three b. four c. six d. eight e. octet 5. Which of the following properties is typically used to predict the type of bond that forms between two elements? a. Electronegativity b. Ionization energy c. Atomic radius d. Electron affinity e. Powerpoint 6. Electronegativity increases from left to right across a period because of a. the electronegativity trend rule b. the increase of Z eff across the period due to increasing nuclear charge c. the decrease of Z eff across the period due to shielding d. the laws of conservation of electronegativity e. cancellation of wave function due to shielding

3 Page 3 7. Which element has the highest electronegativity? a. Al b. C c. O d. Cs e. Rb 8. Which of the following lists the elements from smallest to largest atomic radius? a. Cs, Rb b. Si, As c. Mg, He d. Zr, Sc e. none of the above 9. Indicate the element with the greatest first ionization energy. a. Cs b. Sr c. S d. O e. Fr 10. Which of the following elements has the greatest electron affinity? a. H b. Sn c. P d. Sr e. they are all the same at 0 kj/mol

4 Page Which of the following bonds is definitely ionic? Element Electronegativity C 2.5 O 3.5 H 2.1 Li 1.0 a. Li-C b. Li-H c. Li-O d. Li-Li e. C-O 12.A resonance structure indicates that there is a. more than one allotropic form of a compound. b. more than one ionic form of a compound. c. more than one way to draw a compound s Lewis structure. d. more than one isotopic form of an element. e. more than one electronegativity in the molecule. 13. Which of the following is a resonance structure of the chlorite ClO 2 - ion? 14.Vinegar is a solution of acetic acid (C 2 H 4 O 2 ) and water. Which of the following is the Lewis structure for acetic acid?

5 Page What is the formal charge of the nitrogen atom in hydrogen cyanide (HCN)? a. 1 b. 0. c. -1 d. 5 e On the basis of formal charge, which of the following possible resonance structures of the perchlorate ion (ClO 4 - ) is most stable? 17. Indicate which type of molecular orbital results from a buildup of electron density between two nuclei. a. σ b. π c. σ* d. π* e. δ 18. Which one of the below correctly arranges the bond lengths between two atoms from longest (left) to shortest (right)? a. C-C, C = C, C=C b. N = N, N=N, N-N c. O-O, O=O d. C=O, C-O e. Cl=O, Cl-O

6 Page Which of the following molecules is paramagnetic? (Hint: you may use the figure attached on the back) a. Be 2 b. C 2 c. N 2 d. B 2 e. F 2 Questions Below Here Are For Chapter Which of the following cannot absorb infrared radiation a. HCl b. SiH 4 c. N 2 d. C 6 H 6 e. NO 2 21.Increased emission of CO 2 due to fossil-fuel consumption has been predicted to lead to a 1.0º-3.5º C rise in Earths surface temperature during the twenty-first century. Which of the following might offset such global warming? a. increased emission of methane (CH 4 ) from cows b. increased cloud formation due to the increased evaporation of water c. increased clear-cutting of old-growth forests d. decreased growth of phytoplankton in the oceans e. increased production of CO 2 by burning more fossil fuel. 22.Objects warmed by absorbing visible radiation from the Sun emit radiation in the region of the spectrum. a. ultraviolet b. visible c. infrared d. microwave e. gamma ray 23. Infrared spectra usually measure the of radiation by vibrational modes in molecules. a. emission b. scattering c. diffraction d. absorption e. reflection 24. Which of the C to O bonds in the following molecules do you expect to absorb the longest wavelength infrared radiation? a. the C O bond in CH 3 OH (methanol) b. there is no way to tell. c. C O d. the C=O bond in CO 2 e. the C=O bond in H 2 CO (formaldehyde)

7 Page How many valence electrons are there surrounding the iodine atom in the iodate ion (IO 3 - )? a. 8 b. 10 c. 5 d. 4 e Which of the following atoms can have an expanded octet? a. H b. C c. N d. B e. Se 27. ClO is an important intermediate in the decomposition of stratospheric ozone. What is the proper Lewis structure for this molecule? Useful information: Electronegativities Cl = 3.0, O = 3.5. a. Cl O b. Cl O c. Cl O d. Cl O e. Cl O 28. Using the MO diagram (valence orbitals only) for ClO shown below determine the actual bond order for the ClO molecule. Cl ClO O E 3p σ p π 3s 2s σ a. 1.5 b. 2.0 c. 2.5 d. 3.0 e Based on the MO diagram below and the fact that nuclei with odd numbers of protons like N cause a triple splitting in ESR (electron spin resonance spectra), what will be observed if you take an ESR spectrum of ClO? Cl ClO O π σ p σ σ p 2p E 3p 3s π σ p π σ σ 2s 2p a. a single peak b. a double peak c. a triple peak d. a broad peak e. no peak 30. Molecular geometry is determined by a. electron-proton attractive forces. b. electron-electron attractive forces. c. nuclear attractive forces. d. electron-electron repulsive forces. e. nuclear repulsive forces.

8 Page Which of the following is a square planar molecule? In the molecules below the central atom underlined. a. NH 3 b. PCl 5 c. KrF 4 d. CH 3 COOH e. SO Determine the molecular geometry of CF 2 Cl 2. a. linear b. bent c. trigonal bipyramidal d. tetrahedral e. square planer 33. Which of the following molecules has the smallest H A H bond angle, where A represents the central atom? In the molecules below the central atom is underlined. a. SiH 4 b. H 2 S c. H 2 CO d. CH 3 OH e. BH Which of the following molecules is expected to be square pyramidal? a. NH 4 + b. PCl 5 c. PCl 4 O (P is the central atom) d. [AlCl 4 O] 3- (Al is the central atom) e. XeF Which of the following molecules has a carbon atom that is sp 3 hybridized? a. C 2 H 2 b. H 2 CO c. CH 3 Cl d. C 2 H 4 e. H 2 CS 36. Which of the following has a central atom with the same hybridization as the oxygen in water? a. SO 2 b. OCS c. CS 2 d. NH 3 e. XeF 2

9 Page What is the hybridization of the central iodine in I 3 -? a. sp b. sp 2 c. sp 3 d. sp 3 d e. sp 3 d What type of hybridization will lead to a "T-shaped" molecule? a. sp 3 d 2 b. sp 3 d c. sp 3 d. sp 2 e. sp 39. Which of the following diagrams shows the correct orientation of the dipole moment of COCl 2? a. b. c. d. e. none of these 40.What is the partial charge in fractions of an electron on the Br atom in HBr if the dipole moment is 0.78 D and the bond length is 2.67 pm? Useful constants: 1 D = x C m, charge on electron e = 1.60 x C. a x 10 1 e b. 9.7 x C c. 2.9 x 10 9 D/m d. 1.8 x e e e