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DAWSON COLLEGE DEPARTMENT OF CHEMISTRY & CHEMICAL TECHNOLOGY FINAL EXAMINATION CHEMISTRY 202-NYA-05 December 20, 2007 9:30 A.M. – 12:30 PM Print your Name:__________________________________________ MARK DISTRIBUTION Student Number:____________________________ 1. /5 2. /6 3. /5 4. /7 5. /5 INSTRUCTIONS: 6. /6 This exam set consists of 16 questions. Please ensure that your copy of this examination is complete. 7. /8 Answer all questions in the space provided. 8. /6 1. Calculators may not be shared. Programmable calculators are not permitted. 9. /5 10. /6 11. /9 12. /7 13. /4 14. /6 15. /8 16. /5 Significant Figures /1 Units /1 TOTAL /100 INSTRUCTORS: Please circle the name of your instructor: J. Ali D. Baril O. Behar H. Doan I. Dionne M. Di Stefano M. Haniff S. Harrison H. Khouri D. Montecalvo S. Mutic R. Squire Y.-S. Uh D. Vukadin 2. No books or extra paper are permitted. 3. In order to obtain full credit, you must show the method used to solve all problems involving calculations and express your answers to the correct number of significant figures. 4. Your attention is drawn to the College policy on cheating. This policy will be enforced. 5. A Periodic Table is provided. You may detach the Periodic Table. USEFUL DATA: Avogadro’s Number NA = 6.022 x 1023 mol–1 Gas Constant R –1 = 2.178 x 10–18 J 7 –1 Rydberg Constant RH = 1.0974 x 10 m Planck’s Constant h = 6.626 x 10–34 J⋅s Speed of light c = 2.998 x 108 m⋅s–1 Mass of an electron me = 9.11 x 10–31 kg Mass of a proton mp = 1.67 x 10–27 kg 1 atm = 101.3 kPa = 760 mmHg = 760 torr 1 J = 1 kg⋅m2⋅s–2 –1 = 0.08206 L⋅atm⋅K ⋅mol = 8.314 L⋅kPa⋅K ⋅mol = 8.314 J⋅K–1⋅mol–1 Bohr Orbit Constant B –1 –1 Question 1 a. Write the formula of each of the following compounds. i. Dinitrogen monoxide ii. Copper (II) sulfate pentahydrate iii. Tin (IV) oxide iv. Phosphorous acid v. Ammonium hydrogen sulfate b. Name each of the following compounds. i. MnS2 ii. HClO4 (aq) iii. NH4C2H3O2 iv. Li3N v. Na2O2 (2.5 marks) (2.5 marks) 2 Question 2 Determine the empirical formula and the molecular formula of hydrogen tetrathionate (226.3 g/mol) that gives the following mass percentages upon analysis: H = 0.91% Ans. empirical formula: S = 56.67% (6 marks) O = 42.42% Ans. molecular formula: 3 Question 3 (5 marks) Limestone, CaCO3, reacts with hydrochloric acid to form calcium chloride, water and carbon dioxide according to the following reaction: CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g) How many liters of CO2 gas will be formed at 755 torr and 33.0°C by the reaction of 2.35 g of limestone with an excess of hydrochloric acid? Assume 100% yield and that the gas is ideal. Ans. volume of CO2 gas formed: 4 Question 4 Cisplatin is an anticancer agent used for the treatment of solid tumors such as in breast cancer and is prepared by reacting potassium tetrachloroplatinate (K2PtCl4) and ammonia (NH3). The other product generated is KCl. Cisplatin a. Write the balanced equation for this reaction (1 mark) If 10.00 g of potassium tetrachloroplatinate is mixed with 0.500 g of ammonia (NH3): b. Identify the limiting reactant and calculate the theoretical yield. Ans. Limiting reactant: (4 marks) Ans. theoretical yield: c. If 3.52 g of Cisplatin is actually produced, what is the percent yield of Cisplatin? (2 marks) Ans. %yield of Cisplatin: 5 Question 5 a. Complete and balance the following molecular equation. Fe(NO3)2 (aq) + NH4OH (aq) (2 marks) → Give the physical state in brackets, ex: liquid = (l), for each of the substances participating to the reaction. Write also the complete ionic equation (C.I.E.), identify the spectator ions and write the net ionic equation (N.I.E.) for this reaction. (1.5 marks) C.I.E. Spectator ions: N.I.E. b. Classify each of the following reaction as: precipitation, acid-base (1.5 marks) or oxidation-reduction (red-ox) Chemical reaction i C6H12O6(s) + ii Lead(II) acetate(aq) + iii 6O2(g) → Classification 6CO2(g) + 6H2O(g) Sodium Lead(II) Sodium → + sulfate(aq) sulfate(s) acetate(aq) Copper(II) + Zinc metal → Chloride(aq) Cu(s) + ZnCl2(aq) 6 Question 6 a. Assign oxidation state (or oxidation numbers) to nitrogen in each of the following compounds: i. N2H4 iii. Na3N ii. N2O3 iv. NO3 — b. Balance the following oxidation-reduction reaction in an aqueous basic solution using the half-reaction method. — ClO3 (aq) + N2H4(aq) → (2 marks) NO(g) + (3 marks) — Cl (aq) Ans. balanced reaction: c. Identify the substance being oxidized (0.5 mark) d. Identify the reducing agent (0.5 mark) 7 Question 7 a. Calculate the de Broglie wavelength (in meters) of a proton that is traveling at 25.0% of the speed of light. (3 marks) Ans. de Broglie wavelength: b. One of the emission lines of the hydrogen atom has a wavelength of 656.3 nm. i. In what region of the electromagnetic spectrum (ex: X-ray, UV, etc.) is this emission line found? (1 mark) ii. Calculate the energy of the photon emitted by this transition. (2 marks) iii. Determine the initial or the final n value associated with this emission line if one of the two energy levels is n = 2. (2 marks) 8 Question 8 a. Supply the missing quantum number(s) or sublevel names (or subshell): n l i ii 3 iii ml subshell 0 4p (3 marks) -2 0 2s b. Consider the element with the ground-state electron configuration 1s22s22p4 c. i. identify this element (name or atomic symbol) (0.5 mark) ii. write its electron configuration using the orbital diagram (box notation) (0.5 mark) Consider the atom chromium, Cr i. Write its complete ground-state electron configuration (0.5 mark) ii. What is the number of unpaired electrons in Cr atom? (0.5 mark) d. Give the set of quantum numbers for the circled electron in the following orbital diagram: (1 mark) 9 Question 9 (5 marks) Indicate on this blank outline of a periodic table, which element is described by each of the following. Place the letter of the question (a, b, c, etc) in the correct element box. Messy answers will not be marked. a. b. c. d. e. f. g. h. i. j. Smallest atomic radius in Group 6A Largest atomic radius in Period 6 Condensed ground-state electron configuration is [Ne] 3s23p2 The period 4 member whose (2-) ion is isoelectronic with Kr A transition metal ion with a charge of 1+ having 5 unpaired “4d” electrons The element with the highest first ionization energy in period 4 The excited electron configuration is 1s22s22p63s13p1 The halogen with the smallest electron affinity (less exothermic) The noble gas with electrons occupying 4f orbitals The least electronegative transition metal in period 5 10 Question 10 a. Draw all the possible Lewis structures (resonance forms) for the following ion with carbon as the central atom: SCN (3 marks) — b. Assign formal charges to each atom in each structure. c. Indicate the most appropriate structure according to the formal charges? (2 marks) (1 mark) 11 Question 11 Complete the table below. For each of the following molecules: a. Draw the Lewis structure. Also give the name of the electron-pairs arrangement. b. Make a “3D”-sketch of the molecule with the bond angles and provide a name for the molecular structure (or shape of the molecule) Molecule Lewis structure with all the lone pairs name of the electron-pairs arrangement (9 marks) 3D-sketch (VSEPR) with bond angles Is this a polar molecule? name of the shape of the molecule (Y / N) PH3 BrF3 SO2 12 Question 12 The structure for the amino acid methionine is given below. a. Complete the structure by adding all missing lone pairs of electrons. b. Complete the table for each of the atoms labeled 1 to 6. For each labeled atom, give the hybridization, the bond angle and the number of σ and π bonds around the atom. Atom 1 Atom 2 Atom 3 Atom 4 Atom 5 (1 mark) (6 marks) Atom 6 Hybridization Bond angle no angle Number of σ bonds around the atom Number of π bonds around the atom Question 13 a. Write the name of the most important intermolecular force that keeps the following molecules in the liquid phase. (3 marks) i. CH3F ii. H2O iii. Br2 b. Arrange the following three substances in order of increasing boiling point. HCl, Low boiling point < HF, (1 mark) HBr < High boiling point 13 Question 14 a. Sketch the phase diagram for carbon dioxide (CO2) from the following data: i. The triple point is at 5.2 atm, and –57°C ii. The critical point is at 72.8 atm, and 31°C. iii. At a pressure of 1 atm, the solid-gas phase transition takes place at –78°C iv. At a pressure of 72.8 atm, the solid-liquid phase transition occurs at –21°C (4 marks) Don’t forget to label your axes and to indicate the phase (ex: g, l, s) in each region From your phase diagram, answer the following questions: b. For CO2 at 5 atm and —50°C, what is the stable phase present (gas, liquid, etc.)? (1 mark) c. What phase changes occur when the pressure of a sample of CO2 is decreased from 70 atm to 7 atm at a constant temperature of 0°C ? (1 mark) 14 Question 15 a. Calculate ΔH for the overall reaction: 4NO2(g) using the following data 2N2O5(s) 2NO(g) + → + (4 marks) O2(g) 4NO(g) O2(g) → 2N2O5(s) + → 3O2(g) 2NO2(g) ΔH = 447.4 kJ ΔH = —114.2 kJ Ans. ΔH overall reaction: b. For the reaction below: H⎯C≡N(g) + 2H2(g) → (g) ΔH = —158 kJ Calculate the bond energy for the C≡N triple bond from the following data: Bond Bond energy (kJ.mol-1) H⎯H 432 C⎯H 413 C⎯N 305 N⎯H 391 (4 marks) Ans. C≡N bond energy : 15 Question 16 You want to determine the Cu(II) concentration in an unknown solution by titration. You will first precipitate Cu2+ from the solution by adding an excess of iodide ion Cu2+(aq) + — I (aq) → CuI(s) + I2(aq) (5 marks) [unbalanced] The corresponding amount of iodine (I2) formed will then be titrated with a sodium thiosulfate solution: — S2O32-(aq) + I2(aq) → S4O62-(aq) + I (aq) [unbalanced] The end-point of the titration is reached when all the I2 has reacted. At this point, the violet starch indicator has turned white. Use the following values from the laboratory data sheet to calculate the concentration of Cu2+ in the unknown. Fill-in the blanks Volumetric analysis of Cu2+ DATA SHEET a. Write the overall stoichiometric equation b. Results and observations Unknown no: 20 Concentration of the standard Na2S2O3 solution, M 0.0206 Initial burette reading, mL Final burette reading (mL) Volume of Na2S2O3 used (mL) Number of mole of Na2S2O3 used Number of mole of Cu2+ in the unknown sample Volume of the original Cu2+ solution used (mL) Concentration of the Cu2+ in the original solution (M) 0.17 9.82 10.00 (from a 10 mL pipette) 16 Periodic Table of the Elements 1A 8A 1 2 1 H He 1.008 2A 3 4 2 Li Be 6.9419.012 11 12 22.9924.31 3B 4B 5B 22 4 K Ca Sc Ti 20 4A 5A 6A 7A 4.003 5 6 7 8 9 10 B C N O F Ne 10.8112.0114.0116.0019.0020.18 3 Na Mg 19 3A 21 13 14 15 16 17 18 Al Si P S Cl Ar 26.9828.0930.9732.0735.4539.95 6B 7B 8B 9B 10B 1B 2B 23 24 25 26 27 28 29 30 V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 31 32 33 34 35 36 39.1040.0844.9647.8750.9452.0054.9455.8558.9358.6963.5565.3969.7272.6174.9278.9679.9083.80 38 39 40 5 Rb Sr 37 Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te 41 42 43 44 45 46 47 48 49 50 51 52 53 54 I Xe 85.4787.6288.9191.2292.9195.9498.00101.1102.9106.4107.9112.4114.8118.7121.8127.6126.9131.3 76 77 78 6 Cs Ba La* Hf Ta W Re Os 55 56 57 72 73 74 75 Ir Pt Au Hg Tl Pb Bi Po At Rn 79 80 81 82 83 84 85 86 132.9137.3138.9178.5181.0183.8186.2190.2192.2195.1197.0200.6204.4207.2209.0209.0210.0222.0 87 88 89 104 105 106 107 108 109 110 111 112 7 Fr Ra Acª Rf Db Sg Bh Hs Mt Uun Uuu Uub = metalloid 223.0226.0227.0261.0262.0263.0262.0265.0266.0269.0272.0277.0 58 *Lanthanides 59 60 61 62 63 64 65 66 67 68 69 70 71 Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 140 141 144 145 150 152 157 159 163 165 167 169 173 175 90 ªActinides 91 92 93 94 95 96 97 98 99 100 101 102 103 Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr 232 231 238 237.1 244 243 247 247 251 252 257 258 259 260 17