School of Chemistry and Physics Westville Campus, Durban. Examination: May 2012 CHEM 110: GENERAL PRINCIPLES OF CHEMISTRY

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1 School of hemistry and Physics Westville ampus, urban ROE Examination: May 2012 HEM 110: GENERL PRINIPLES OF HEMISTRY Total Marks for Section : 60 uration: 3 Hours Total marks for Examination: 100 Internal Examiners: r P Ndungu, r V Paideya, Mrs H Govender, Ms G awson Moderators: r M kerman, r Reddy, r S Ojwach, r Southway IMPORTNT: omplete this part immediately. Student No. Seat Number: Name (optional) INSTRUTIONS: 1. nswer LL questions. 2. alculators may be used. 3. The pages of this paper must not be unpinned. 4. Your answers must be written on the MQ sheet provided. 5. Use H Pencil and Tipp-Ex TM are not allowed. 6. This is Section : Multiple hoice Questions, consisting of 18 pages. 7. You are advised to spend not more than 2 hours on Section. 8. periodic table and a data sheet are provided at the end of the Multiple hoice Questions Section Section Section Total Total Maximum Internal Mark External Mark

2 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry SETION : Multiple hoice Questions 1. What is the volume of 30.0 g of methanol (H 3 OH(l), density = g ml -1 )? 26.3 ml 33.3 ml L 37.9 ml 2. lassify the following substances (i) copper oxide (ii) copper metal (iii) copper alloy s an element, compound, homogeneous mixture or heterogeneous mixture. (i) heterogeneous (ii) compound (iii) element (i) heterogeneous (ii) compound (iii) homogeneous (i) compound (ii) element (iii) homogeneous (i) homogeneous (ii) element (iii) heterogeneous 3. Indicate how many significant figures are present in the following quantity? ml Page 2 of 18

3 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 4. alculate the following arithmetic functions and round off your answers to the correct number of significant figures: 2.78 x ( ) How many protons, neutrons, and nucleons are present in an atom of the platinum isotope 194 Pt? 78 protons, 116 neutrons, 194 nucleons 78 protons, 38 neutrons, 116 nucleons 116 protons, 78 neutrons, 194 nucleons 78 protons, 194 neutrons, 78 nucleons 6. alculate the mass of 1.16 x molecules of N g N g N g N g N 2 Page 3 of 18

4 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 7. The chemical formula for copper(i) phosphate is: u 2 PO 4 u 2 PO 3 u 3 PO 4 upo 8. Which of the following are combination reactions? I. H 4 (g) + O 2 (g) O 2 (g) + H 2 O(l) II. ao(s) + O 2 (g) ao 3 (s) III. Mg(s) + O 2 (g) MgO(s) IV. PbO 3 (s) PbO(s) + O 2 (g) I, II, and III II and III all of them IV only 9. Using IUP rules give the name of Fe 2 S 3 Iron sulfide Iron(III) sulfide Iron(III) sulfate Ferric(II) sulfate Page 4 of 18

5 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 10. Give the formula for initrogen pentoxide N 2 P 2 O 5 N 2 O 5 NO 5 N 2 PO mole of silver nitrate reacts with 1.6 moles of Hl in a precipitation reaction to produce gl and nitric acid. The following reaction occurred: gno 3 (aq) + Hl(aq) gl(s) + HNO 3 (aq) How many moles of HNO 3 are produced? The % (m/m) hydrogen in sprin ( 9 H 8 O 4, g mol -1 ) is % % 4.45 % % Page 5 of 18

6 6 H 10 O 2 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 13. Ethyl acetate is composed of 54.4%, 9.17% H and 36.39% O by mass. The empirical formula of ethyl acetate is: H 2 O 4 H 8 O 2 2 H 4 O None of the above 14. etermine the molecular formula for adipic acid if it has an empirical formula of 3 H 5 O, and a molecular mass of u. 3 H 5 O 5 H 6 O 3 9 H 15 O 15. You are provided with 1.00 mol of Mg and mol of iron(iii) oxide. The balanced equation for the reaction is: 3Mg + Fe 2 O 3 3MgO + 2Fe What is the limiting reagent for the production of MgO? Mg Fe 2 O 3 MgO Fe Page 6 of 18

7 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 16. Which of these compounds is insoluble in water? Ni(NO 3 ) 2 Pbl 4 gl FeSO Which of the following pairs of aqueous solutions will give a precipitate when mixed? ao 3 and Hl Mg(NO 3 ) 2 and NaOH gno 3 and a(lo 4 ) 2 NaOH and H 3 OOH 18. onsider the following equation and select the correct products FeS(s) + 2H + (aq) H 2 S(s) + Fe 2+ (aq) H 2 S(aq) + Fe(s) H 2 S(g) + Fe 2+ (aq) no reaction occurs Page 7 of 18

8 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 19. In the reaction between aqueous copper(ii) sulfate and sodium carbonate, which are the so-called "spectator" ions? u and O 3 Na + 2- and SO 4 Na + 2- and O 3 None of the above 20. Identify the reducing agent in the following balanced reaction: 3SO 3 2 (aq) + 2MnO 4 (aq) + 2H + (aq) 3SO 4 2 (aq) + 2MnO 2 + H 2 O SO 3 2 MnO 4 SO 4 2 MnO Real gases are most like ideal gases at high pressure and high temperature. high pressure and low temperature. low pressure and high temperature. low pressure and low temperature. Page 8 of 18

9 l 3+, P 3 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 22. Which one of the following sets of quantum numbers is NOT allowed? n = 3, l = 2, m l = 1 n = 3, l = 0, m l = 0 n = 3, l = 3, m l = 1 n = 3, l = 2, m l = Which pair of particles has the same number of electrons? F, Mg 2+ r, Se Ne, r 24. n atom of Fe has two 4s electrons and six 3d electrons. How many unpaired electrons would there be in an atom of iron? one two three four Page 9 of 18

10 [Kr]4d 10 5p 2 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 25. The ground state electron distribution for the Sn 2+ ion is [Kr]4d 10 5s 1 5p 1 [Kr]4d 10 5s 2 5p 2 [Kr]4d 10 5s admium normally forms the ion d 2+, whereas silver gives the g + ion. What is an explanation of these facts? Silver has two 5s electrons, one of which is more difficult to remove than the other. The 4d subshell in silver is completed to give a more stable structure, leaving only one electron in the 5s subshell. admium loses two 4d electrons to form the d 2+ ion. None of these is correct. 27. Which is the correct Lewis structure for S 2? : S S : : : : S S : : : :S S : : : :S S : : : Page 10 of 18

11 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 28. Which of the following atoms or ions has eight valence electrons? Kr I Na + ll of the above 29. Which of the molecules below has the most polar bond? HI Hr Hl HF 30. Which structure does not obey the octet rule? SbF 3 NF 3 PF 3 IF Which of the following molecules has a square planar geometry? PH 3 XeF 2 Il 3 XeF 4 Page 11 of 18

12 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 32. n electron domain consists of i) a nonbonding pair of electrons ii) a single bond iii) a multiple bond i only ii only iii only i, ii, and iii 33. For which of the following molecules, shown below, is the molecular geometry (shape) the same as the VSEPR electron domain arrangement (electron domain geometry)? (i) Pl 3 (ii) l 4 (iii) XeF 4 (iv) SF 6 (i) and (ii) (iii) and (iv) (i) and (iv) (ii) and (iv) 34. For which one of the following elements is ΔH f not zero? O 2 (g) l 2 (g) F 2 (s) (graphite) Page 12 of 18

13 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 35. For which one of the following reactions is the value of ΔH rxn equal to ΔH f for the product? ½N 2 (g) + O 2 (g) NO 2 (g) H 2 (g) + ½O 2 (g) H 2 O(l) 2(s, graphite) + 2H 2 (g) 2 H 4 (g) ll of the above 36. Which substance in the reaction below either appears or disappears the fastest? 4NH 3 + 7O 2 4NO 3 + 6H 2 O H 2 O O 2 NH 3 The rates of appearance/disappearance are the same for all of these. 37. Which of the following units cannot be used as a valid unit to express a reaction rate mol/hr mol/l hr M/s mol/l Page 13 of 18

14 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 38. With regards to the reaction quotient of a reaction (Q) and the equilibrium constant K eq, choose the correct statement below: K eq does not change with temperature, whereas Q is temperature dependent. K eq depends on the concentrations or partial pressures of reaction components. Q does not depend on the concentrations or partial pressures of reaction components. Q is the same as K eq when a reaction is at equilibrium. 39. Which of the following equilibria, will shift to the left in response to a decrease in volume? H 2 (g) + l 2 (g) 2Hl(g) N 2 (g) + 3H 2 (g) 2NH 3 (g) 2SO 3 (g) 2SO 2 (g) + O 2 (g) 4Fe(s) + 3O 2 (g) 2Fe 2 O 3 (s) 40. omplete the following statement by selecting the appropriate letter below. The effect of a catalyst on an equilibrium is to. shift the equilibrium to the right. increase the rate at which equilibrium is achieved without changing the composition of the equilibrium mixture. slow the reverse reaction only. increase the rate of the forward reaction only. Page 14 of 18

15 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 41. The value of ΔH for the reaction below is 1107 kj: 2a(s) + O 2 (g) 2aO(s) alculate the amount of heat released when 5.75 g of a(s) reacts completely with oxygen to form ao(s). 26.3kJ 96.3kJ 46.4kJ 23.2kJ 42. Select the correct statement: Electronegativity decreases from left to right along a row of the periodic table, and increases from top to bottom within a group Electronegativity increases from left to right along a row of the periodic table, and increasesfrom top to bottom within a group Electronegativity increases from left to right along a row of the periodic table, and decreases from top to bottom within a group Electronegativity increases from left to right along a row of the periodic table, and stays the same from top to bottom within a group Page 15 of 18

16 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 43. alculate the formal charge on N in the nitrate anion: Which statement is incorrect? Resonance structures are equivalent Lewis diagrams (structures) used to represent one molecule. Formal charge is used as a guideline to determine the most accurate Lewis structure out of a number of different possibilities. Formal charge can always be used to determine the actual charge on an atom in a molecule. Lewis structures are a simplified model that illustrates how valence electrons are shared between covalent compounds. Page 16 of 18

17 Rate = k{] 2 [] School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 45. If the rate law for the reaction products is first order in and second order in, then the rate law is: Rate = k[][] Rate = k[][] 2 Rate = k[] 2 [] 46. The kinetics of the reaction below were studied and it was determined that the reaction rate increased by a factor of 9 when the concentration of was tripled. What is the order with respect to? + P Second First Zero One-Half 47. alculate the [H + ] concentration, in mol dm -3, for an aqueous solution with a ph of Page 17 of 18

18 School of hemistry and Physics University of KwaZulu-Natal, Westville ampus HEM110/195: General Principles of hemistry 48. K w for water at 37 is The ph of a neutral aqueous solution at this temperature is [Total Marks: 60] End of Section Page 18 of 18