POLYTECHNIC OF NAMIBIA DEPARTMENT OF HEALTH SCIENCES BACHELOR OF ENVIRONMENTAL HEALTH SCIENCES HEALTH SCIENCE CHEMISTRY (HSC 511S) NQF level 5 SECOND OPPORTUNITY EXAMINATION November 2014 TIME: MARKS: PAPER: PAGES: 3 hours 100 1 12 (Including cover page) INSTRUCTIONS: 1. Answer all questions. 2. Please write neatly and legibly. 3. Show all steps used in calculations. 4. No books, notes and other additional aids are allowed. 5. Only a scientific calculator is allowed. 6. Marks all answers clearly with their respective question numbers. 7. The useful constants and Periodic Table are provided on pages 11 and 12, respectively. EXAMINER: MODERATOR: DR. H. M. KWAAMBWA DR. M. MUTORWA I
SECTION A QUESTION I (60] There are 20 multiple choice questions in this section. Each question carries 3 marks. Answer ALL questions by selecting the letter of the correct answer. 1.1 The result of38.7 em x 9.1 em is: A. 352 cm 2 B. 352 em c. 350cm D. 350 cm 2 E. 352.17 cm 2 1.2 A liquid has a density of0.89 g/ml. Calculate the volume of 1.0 kg of this liquid. A. 1.12 L B. 890 ml C. 1.12 ml D. 890 L E. 112m 3 1.3 Of the following statements about the number of subatomic particles in an ion of 32 S,_, which is (are) true? I. 16 protons II. 14 neutrons III. 18 electrons A. II only B. III only C. I and II only D. I and lii only E. I, II, and III 2
1.4 Which one of the following sets of quantum numbers, { n, l, m 1, m,}, describing an electron in the indicated orbital, is NOT CORRECT (is not possible)? A. {1, 0, 0, 1/2}, 1s B. {5, 2, 2, 1/2}, 5p c. {3, 2, -1, 1/2}, 3d D. {3, 1, 1, 1/2}, 3p E. {4, 0, 0, 1/2}, 4s 1.5 The number of electrons in the 3d orbital of the atom of atomic number 23 is: A.4 B. 3 C. 5 D. 6 E. 2 1.6 For a particular organic compound, which of the following pairs can represent the empirical and the molecular formulas, respectively? A. CHand Cl!4 B. CH2 and C2lh C. CH2 and C2H3 D. CH3 and C3H6 E. CHand C6H6 1. 7 The most active metallic elements are found in: A. The upper right corner of the Periodic Table B. The lower right corner of the Periodic Table C. The upper left comer of the Periodic Table D. The lower left comer of the Periodic Table E. The middle of the table, just beyond the transition elements 3
1.8 Which of the following groups of elements is arranged correctly in order of increasing ionization energy? A. C <Si <Li <Ne B. Ne < Si < C <Li C. Li<Si<C<Ne D. Ne < C < Si <Li E. None of the above 1.9 A compound contains only Nand 0. A sample of this compound contains 0.2801 g of Nand 0.1600 g ofo. What is the empirical forrnulaofthis compound? A. NOz B. NO C. N03 D. NzO E. Nz03 1.10 The mass percent of oxygen in Na 2 B 4 0 7 is A. 22.86% B. 55.65% C. 61.52% D. 69.95% E. 53.85% 1.11 What is the mass, in grams, of 1 mol ofkai(s04)z.12hz0? A. 132 B. 180 C. 394 D. 474 E. 516 4
1.12 If the simplest formula of a substance is CH2 and its molecular mass is 56 amu, what is its true formula? A. CH2 B. C2H4 C. C3H4 D. C4Hs E. CsHw 1.13 At 5 atm pressure and 70 C, how many moles are present in 1.5 L of 0 2 gas? A. 0.036 B. 0.267 C. 0.536 D. 1.60 E. 1.00 1.14 How many ml of 5 M NaOH are required to completely neutralize 2 L of3 M HCl? A. 600 B. 900 C. 1200 D. 1500 E. 1800 1.15 A gas at 43 C has a pressure of 680 torr. If the temperature is raised to 55 C, what will the new pressure of the gas be? (Assume all other variables remain constant). A. 735 torr B. 706 torr C. 870 torr D.!58 torr E. 374 torr 5
1.16 A liter of hydrogen is at 5 C temperature and under 640 torr pressure. If the temperature is raised to 60 C and the pressure is decreased to 320 torr, how will the one liter volume be modified? A.!Lx.2_x 640 60 32 B.!Lx 60 X 320 5 640 C.!Lx 278 x 640 333 320 D. E.!Lx 333 x 640 278 320!Lx 333 x 320 278 640 1.17 Calculate the total pressure for a gas mixture containing 0.0150 mol H2, 4.22 mg He, and 0.0300 mol NH 3 in 500 ml volume at 0 C. A. 2.06 atm B. 1.34 atm C. 2.01 atm D. 0.72 atm E. 1.27 atm 1.18 The initial concentration of a reactant in a first order reaction is 0.42 mol/l. The rate constant for the reaction is 0.16 s- 1 It takes seconds for the reactant concentration to decrease to 0.13 mol/l. A. 0.19 B. 7.3 C. 0.16 D. 6.1 E. 0.13 6
1.19 For a certain reaction A + B ----+ C, it was noted that when the initial concentration of A is doubled while B is held constant, the initial reaction rate doubles, and when the initial concentration of B is doubled while A is held constant, the initial rate increases four-fold. What is the rate expression for this reaction? A. Rate= k[a][b] B. Rate= k[af[bj 3 C. Rate= k[a][b] 2 D. Rate= k[a] 3 [BJ E. Rate = k[ A ] 2 [B] 1.20 Which of the following hydrocarbons must be an alkane? A. C2H2 B. CsHw C. C7H12 D. C14H3o E. None of the above 7
SECTIONB [40] There are SIX questions in this section. Answer all Questions. Show clearly, where necessary, how you arrive at the answer as the working will carry marks too. QUESTION2 [5] The questions (a)- (d) refer to the Periodic group shown, with letter choices substituted for the respective clements. Halogen Group A B c D E (a) The element that is most active chemically (b) The element with the smallest ionic radius (c) The element with the lowest ionisation energy (d) The clement that first shows some metallic properties at room temperature (e) The element with highest mass number 8
QUESTION 3 [9] (a) Which gas from the following will diffuse slowest through a porous plate and why? He (I) (b) What is the number of orbitals that make up the third (n = 3) shell? Show clearly how arrive at you answer. (3) (c) Write the noble gas configuration of the ions S 2 - and Fe 2 +. (2) (d) The speed of light, c, is 3.0 x 10 10 crn!s. What is this velocity in km/hr? (3) QUESTION 4 [6] State briefly what you understand by the following: (a) Half-life of a reactant (b) Charles' law (c) Electron affinity (d) Precision (e) Accuracy (f) Standard temperature pressure (STP) QUESTION 5 [13] An organic liquid analysis gave 24.78% C, 2.08% H, and 73.14% Cl by mass. When 1.789 g of this compound is vaporized at 200 C, the volume of 500 ml has a pressure of 726 torr. For this compound, calculate: (a) the empirical formula. (5) (b) the molar mass. (5) (c) the molecular formula. (3) 9
QUESTION6 [ 4] (a) A solution is prepared by dissolving 35.5 g of Na 2 S0 4 in sufficient lho to produce 500 ml of solution. Calculate the molarity of this solution. (2) (b) How would you prepare 100 ml ofo.ioo M Na 2 S0 4 using the stock solution in (a)? (2) QUESTION 7 [31 Write the IUP AC name of each of the following organic compounds: (a) (b) OH (c) END OF EXAM QUESTIONS 10
USEFUL CONSTANTS: Gas constant, R 8.3145 J mor 1 K. 1 0.083145 dm 3 bar mor 1 K 1 0.08206 L atm mor 1 K 1 I Pa m 3 = I kpa.l I N. m = I J I atm =101 325 Pa 760 mmhg = 760 torr Avogadro's Number, NA = 6.022 X 10 23 mor 1 11
PERIODIC TABLE OF THE ELEMENTS N 18 1 2 H 1.00794 2 13 14 15 16 17 3 4 5 6 7 8 9 10 Li Be B c N 0 F Ne 6.941 9.01218 10.81 12.011 14.0067 15.9994 18.9984 20.179 11 12 13 14 15 16 17 18 Na Mg AI Si p s Cl Ar 22.9898 24.305 3 4 5 6 7 8 9 10 11 12 26.9815 28.0855 30.9738 32.06 35.453 39.948 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 K Ca Sc Ti v Cr Mn Fe Co. Ni Cu Zn Ga Ge As Se Br Kr 39.0983 40.08 44.9559 47.88 50.9415 51.996 54.9380 55.841 58.9332 58.69 63.546 6538 69.72 72.59 74.9216 78.96 79.904 83.8 He 4.00260: 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 Rb Sr y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 85.4678 87.62 88.9059 91.22 92.9064 95.94 (98) 101.07 102.906 106.42 107.868 112.41 114.82 118.69 121.75 127.6 126.9 131.29 55 56 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 Cs Ba Lu Hf Ta w Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 132.905 137.33 174.967 178.49 180.948 183.85 186107 190.2 192.22 195.08 196.967 200.59 204.383 207.2 208.908 (209) (210) (222) 87 88 103 104 105 106 107 108 109 110 111 112 114 11() 118 Fr Ra Lr Rf Db Sg Bb Hs Mt Uun Uuu Uub Uuq Uuh Uuo (223) 226.02S (260) (2611 _(262J 1263) (264) lc265) 1<268) (269) (272) (269) I Q V N Yセ @ Lanthanides: 57 58 59 60 61 62 63 64 65 66 67 68 69 70 La Ce Pr Nd Pm Sm Eo Gd Tb Dy Ho Er Tm Yb! 138.906 140.12 140.908 14414 - (145) 150.36 151.96 157.25 158.925 162.50 161.930 167.26 _11194 Actinides: 89 90 91 92 93 94 95 96 97 98 99 100 101 102 Ac Th Pa u Np Pu Am Cm Bk Cf Es Fm Md No 227.028 232.038 231.036 238.029 237.048 (244) (243).(247} (247) _{251) (252) (257) (258) (259)