Exam 3. Dr. Susan Bates. December 5, Name 9:00 OR 10:00

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1 ID #: Chem 1711 Exam 3 Dr. Susan Bates December 5, 2013 Name 9:00 OR 10:00 h = 6.63 x J s c = 3.00 x 10 8 m/s R = x 10 7 m 1 E = hν = hc/λ = mc 2 1 J = 1 (kg m 2 )/s 2 N A = x mol 1 E Q 1 Q 2 /r λ = h/mv A = log(%t/100) = εbc!e = -Rhc = R 1 1 n 2 f n 2 i " n 2 l n 2 u I A II A III B IV B V B VI B VII B VIII I B II B III A IV A V A VI A VII A inert gases 1 H He Li Na K Rb Cs Fr (223) 4 Be Mg Ca Sr Ba Ra Sc Y * La * Ac (227) 22 Ti Zr Hf Rf (261) 23 V Nb Ta Db (262) 24 Cr Mo W Sg (263) 25 Mn Tc Re Bh (262) 26 Fe Ru Os Hs (265) 27 Co Rh Ir Mt (266) 28 Ni Pd Pt (269) 29 Cu Ag Au (272) 30 Zn Cd Hg (277) 5 B Al Ga In Tl ? 6 C Si Ge Sn Pb (289) 7 N P As Sb Bi O S Se Te Po (210) 9 F Cl Br I At (210) 10 Ne Ar Kr Xe Rn (222) 58 Ce Th Pr Pa (231) 60 Nd U Pm (147) 93 Np (237) 62 Sm Pu (242) 63 Eu Am (243) 64 Gd Cm (247) 65 Tb Bk (247) 66 Dy Cf (251) 67 Ho Es (254) 68 Er Fm (253) 69 Tm Md (256) 70 Yb No (254) 71 Lu Lr (257)

2 Chem 1711 Exam 3 Part I: Short Answer (43 points). Name 1. Which photon of electromagnetic radiation below that has higher energy? Cirlce the one best answer. phonton with λ = 1200 nm photon with ν = 4.63 x Hz 2. True or False? In your Atomic Spectroscopy experiment, lithium ions could be identified by their distinctive, emitted red color. 3. Indicate (by circling) whether each of the following species are paramagnetic or diamagnetic: a. a neutral atom of zinc paramagnetic OR diamagnetic b. a chromium (II) ion paramagnetic OR diamagnetic c. an oxide ion paramagnetic OR diamagnetic 4. Consider a neutral atom of chromium in its ground state. a. Using noble gas core symolism, write the electron configuration for Cr: b. Construct an orbital diagram below to show how the electrons beyond the noble gas core populate atomic orbitals. c. Give a set of quantum number for one core e of Cr: n m m s 5. How many electrons in an atom can have quantum numbers of n = 5 and = 2? 6. Identify (by name) the neutral atom that is isoelectric with Os Determine the wavelength (in m) of an electron travelling with a velocity of 365 m/s. For an e, m = 9.11 x kg. λ = m 8. Determine the energy (in J) of 2 moles of photons with λ = 230 nm. E = J 9. Determine the frequency (in s 1 ) of a photon of light with wavelength = 783 nm. ν = s 1

3 10. Draw a Lewis structure (including all lone pairs of electrons) that obeys the octet rule for each of the following species: a. HSiCl 3 b. SCN (C is the central atom) c. Determine the formal charge on each atom in your structure for b above: S C N 11. Rank the following from smallest to largest first ionization energy: Be, O, Sr < < smallest largest 12. Circle the one atom or ion below that could correspond to the following Lewis symbol: E Al Al 3+ I + Sb In Circle the one element below that is predicted to have the greatest electronegativity: V As Ta 14. Put the following atoms or ions in order from smallest to largest radius: Ca, Ti 4+, Ca Circle the one quantity below that should be the greatest: < < smallest largest / 43 1 st ionization energy of Rb 2 nd ionization enery of Ca 1 st ionization energy of Sr Part II (42 points): Multiple Choice. Indicate the one best answer for each of the following by bubbling in that answer on the provided Scan-Tron sheet. 1. Which element could be represented in its ground state by the following diagram? a. N b. O c. P d. Si e. S 2. Which of the following transitions in a hydrogen atom corresponds to the emission of the shortest λ of light? a. n = 1 to n = 2 b. n = 1 to n = 5 c. n = 2 to n = 1 d. n = 3 to n = 2 e. n = 5 to n = 4

4 3. Which of the following statements about effecive nuclear charge is incorrect? a. Z eff can be approximated by subtracting the number of core electrons from the nuclear charge. b. Electrons in inner shells shield outer shell electrons from feeling the full effect of the charge of the nucleus. c. The effective nuclear charge increases from left to right across a period. d. Increasing the number of shells of orbitals as you go down a group has no effect on the effective nuclear charge. e. Z eff may be invoked to account for the general periodic trend in ionization energies. 4. Which of the following photons has a longer wavelength than red visible light? a. blue light b. IR c. UV d. X-rays e. green light 5. Consider two isolated bonds, C N, and Cl Be. Using your knowledge of the general trends in electronegativity, which atom is expected to bear a partial negative charge in the more polar of these bonds? a. C in C N b. N in C N c. Cl in Cl Be d. Be in Cl Be e. all atoms will bear the same partial charge in these bonds 6. Which of the following changes is exothermic as written? a. Mg + (g) Mg 2+ (g) + e b. MgCl 2 (s) Mg 2+ (g) + 2 Cl (g) c. Mg (g) + e Mg (g) d. Cl 2 (g) 2 Cl (g) e. None of these is exothermic as written. 7. Which of the following statements is/are correct? i. Atomic radius and ionization energy increase across a period because the Z eff increases. ii. Atomic radius decreases down a group because more electrons are held closely to the nucleus. iii. Sulfur has a greater ionization energy than phosphorus because its electrons are farther from the nucleus. a. i b. ii c. ii and iii d. i and ii e. none of these is correct 8. How many electrons are in bonds around the central atom (italicized) in NH 2 F? a. 2 b. 3 c. 4 d. 6 e Which one of the following sets of quantum numbers is not allowed? a. n = 2 = 0 m = 0 m s = 1/2 b. n = 23 = 0 m = 0 m s = 1/2 c. n = 2 = 2 m = 2 m s = 1/2 d. n = 2 = 1 m = 1 m s = +1/2 e. n = 5 = 4 m = 1 m s = 1/2 10. Which of the following ionic compounds would you predict has the largest lattice energy? a. Al 2 O 3 b. KCl c. CaCl 2 d. CsI e. BaF 2

5 11. Consider a small particle such as an electron. According to quantum mechanics, the accuracy of which two quantities is limited by the Heisenberg uncertainty principle? a. charge and mass b. momentum and position c. momentum and charge d. mass and energy e. position and charge 12. Which of the following statements is/are correct? i. The Pauli exclusion principle states that no two electrons in an atom may have the same 4 quantum numbers. ii. The lowest energy arrangement of electrons in an orbital is obtained by pairing electrons with different spins before placing unpaired electrons in degenerate orbitals. iii. The ground state electron configuration of a manganese atom has 5 unpaired electrons. a. ii and iii b. i and iii c. i and ii d. i e. all of these are correct 13. Based on your Spectrophotometry lab, which of the following statements is correct? a. As the concentration of the dye solution decreased, the light passing through the cuvette became more red in color. b. Beer s Law tells us that the wavelength of maximum absorption of light for a compound depends on its electron configuration. c. It is not important to know or record the concentration of your dye solution when measuring absorbance. d. Beer s Law relates the speed of light to the amount of light passing through a sample. e. As the concentration of a dye solution increased, the absorption of light at the wavelength of maximum absorption also increased. 14. Which one of the following element name and symbol pairings is incorrect? a. Nd, neodymium b. Tb, terbium c. Pt, platinum d. Th, thallium e. Ce, cerium /42 Part III (15 points): Written Response and Problems. Complete all 3 questions/problems below. Show all work; work with units in all steps of calculations; report all number answers with appropriate units and significant figures. 1. Consider the IO 3 anion. Draw all of the unique, valid Lewis structures for this ion showing all lone pairs of electrons. Consider the structures you have drawn, and then indicate which is the favored structure by drawing a box around your choice.

6 2. A photon with wavelength of 97.3 nm is emitted by a hydrogen atom. a. Determine the energy (in J) of this emitted photon. Energy = J b. If the hydrogen atom ends up in a ground state configuration, what is the initial principle quantum number of the photon? n i = 3. Hydrogen cyanide may react in the presence of hydrogen gas to form methyl amine according to the following equation: H H H C N (g) 2 H 2 (g) H C H N H (g) a. Which carbon nitrogen bond would you expect to be shorter? Circle one answer below: carbon nitrogen bond in reactant OR carbon nitrogen bond in product b. Determine the H (in kj) for this reaction using the following bond dissociation energy values: H H 432 kj/mol C H 413 kj/mol N H 391 kj/mol C N 305 kj/mol C N 891 kj/mol H = kj /15