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THE UNIVERSITY OF BRITISH COLUMBIA Department of Chemistry CHEM 121 – Section 103 QUIZ #3 (November 3, 2010) LAST NAME: ANSWER KEY FIRST NAME(S): SIGNATURE: STUDENT NUMBER: REGULATIONS REGARDING EXAMINATIONS Candidates guilty of any of the following, or similar, dishonest practices shall be liable to disciplinary action: a) Making use of any books, papers, preprogrammed information in calculators, or other memoranda other than those authorized by the examiners. b) Speaking or communicating with other candidates. c) Purposely exposing written papers to the view of other candidates. The plea of accident or forgetfulness shall not be received. The only acceptable calculator is the Sharp EL-510R. Breach of any of the above regulations will result in the assignment of a grade of zero (0). INSTRUCTIONS I. Write all answers on this paper, being sure to show explicitly all calculations. II. This quiz is out of 10 marks and is printed on both sides of the page. 1. For a particular orbital, n = 5 and m l = -2. What are all of the possible values of l ? (1 mark) l = 4, 3, 2 2. Arrange the following substances in order of increasing boiling point: (1 mark) C H 3 OH LiCl SiH 3 F N 2 HOCH 2 CH 2 OH (backbone O-C-C-O) N 2 < SiH 3 F < CH 3 OH < HOCH 2 CH 2 OH < LiCl l o w e s t h i g h e s t (note that SiH 3 F is polar, but cannot hydrogen bond by itself)
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3. Give the name for one method of isolating sulfur: the _ Frasch or Claus _ process (1 mark) 4. A sample of sulfur dioxide is treated with water to give a solution of compound A . When 0.2 mol of compound A is dissolved in water and treated with 0.4 mol of KOH, 0.2 mol of compound B (molecular weight = 158.3 g mol -1 ) is obtained. In the space below, identify A and B . (2 marks) A = H 2 SO 3 B = K 2 SO 3 5. To which orbitals do the following quantum numbers correspond? (2 marks) (i) n = 7, l = 3 ___ 7f __________ (ii) n = 2, l = 1 ___ 2p __________ * Note that we use lowercase for orbitals 6. The binding energy (work function) of lithium (Li) is 4.6 x 10 -22 J. What wavelength range can be used to remove electrons from lithium metal? Express your answer in nanometres (nm). (e.g., your answer could be 0 to 8 nm and 20 to nm) (2 marks) When the energy of the photon is less than the work function of the metal, no electrons are ejected. For all energies above, electrons are ejected. (Note that the actual value given in this question is incorrect, so the answer you get is not the “real” answer.) Energy of a photon = h ν = hc/ λ Solving, λ = hc/E = (6.626 x 10 -34 J s)(3 x 10 8 m s -1 )/(4.6x10 -22 J) Therefore λ = 4.3 x 10 -4 m = 4.3 x 10 5 nm The question asks for the range. Since this is the wavelength at which electrons begin to be ejected, photons with higher energy (i.e., shorter wavelength) will work. So, any photon with 0 < λ
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