16-final_exam

16-final_exam - CHEMISTRY 16 FINAL EXAM Dr. M....

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Unformatted text preview: CHEMISTRY 16 FINAL EXAM Dr. M. Richards-Babb August 7, 1998 ~ (Version I) An optical scoring machine will grade this examination. The machine is not programmed to accept the correct one of two sensed answers and will not sense answers which are lightly marked. Mark your answer sheet carefully with a No. 2 soft lead pencil and erase any undesired marks COMPLETELY. Avoid making any extraneous marks on the answer sheet other than the information requested below. On the answer sheet: 1. Print your name in the space for NAME (last name first, circle your last name). 9 2. In the space marked SUBJECT print your student number. 3. In the space marked HOUR print Summer II ‘98. Check to see that you have 50 examination questions, periodic table and scratch paper when the exam begins. HAND IN ONLY THE ANSWER SHEET. Useful Equations and Constants: leV = 1 J R = 0.08206 L-atm/mol-K=8.314 J/mol-K F = 96,500'C/mol e' Kw= 1.0x10‘” at 25°C KKHZO)=1.86 kg-°C/mol Kb(HZO)=0.52 kg-°C/mol x= [ -b:‘t (b2 - 4ac)'/']/2a ln[A] = ln[A]0 + -kt OR log[A] = log[A]o + -kt/2.303 [Al/[Alo = CXPHG) 1/[A] = l/[A]0 + kt AG =‘ AG° + RTan ' A ° = -nFE° AG° = -RTan - E = E° - (RT/nF)an If 0.0339 mol of a nonelectrolyte is dissolved in 0.0550 kg of benzene C6H6, the freezing point of the resulting solution is: (Kf(C6H6)=5. 12 kg-°C/mol; T,(C6H6)=+5.48°C) A. +8.64°C B. +4.66°C C. -1.57°C D. +2.32°C E. -3.61°C C4H8 decomposes by first order kinetics with k=9.2><10” sec" at 500°C. How long will it take for a 0.100 M sample of CH; to decompose to 20% of its original value at 500°C? A. ' 175 sec B.‘ 21 sec C. 110 sec D. 250 sec E. 57 sec Refer to the reaCtion below. If the rate of dis'appearance of N205 is 6.0><10‘3 M/sec, then the rate of appearance of N02 is: 4N205 —+8N02+202 3.0><10'3 M/sec 6.0X10'3 M/sec 1.2x 10'2 M/sec 4.8><10'2 M/sec mpow>' Not enough information is given to answer this question. The pH of apples is 3.10. The concentration of hydronium ion H30“ in apples is: A. 7.9x10" M B. '6.5x10"2 M C. 1.0><10'7 M D. . 3.1 X10'9 M E. 1.3><10"l M The pH of 0.0025 M NaOH is: A. 2.60 B. 11.70 C. 11.40 D. 9.86 E. 7.25 Fol SnS has Ksp=3.23 x104“. Addition of HCl will the solubility of SnS in water, while addition of K28 will the solubility. SnS(s) HSn*2(aq) + S‘2(aq) Kw=3.23><10'28 increase; decrease increase; increase decrease; decrease decrease; increase not alter; decrease FIDO??? A certain reaction is endothemiic (AH=+) and entropy is decreasing (AS=-) from reactants to products. Which one of the following statements pertaining to the reaction spontaneity is TRUE? A. The reaction islspontaneous at all temperatures. B. The reaction is nonspontaneous at low temperatures but spontaneous at high temperatures. C The reaction is nonspontaneous at all temperatures. D. The reaction is spontaneous at low temperatures but nonspontaneous at high temperatures. E. There is no way to decide without the value for AG. Sodium reacts violently with water according to the equation: 2 Na(s) + 2 H20(l) -’ 2 NaOH(aq) + H2(g) The resulting solution has a higher temperature than the water prior to the addition of sodium. The signs for AH° and AS° are: AH° is positive and AS° is positive. AH° is negative and AS° is positive. Not enough information given. Need standard heats of formation and molar entropies _ to calculate AH° and AS°. D. AH° is positive. and AS° is negative. E AH° is negative and 138° is negative. ow? Calculate AS° for the' following reaction: I N2(g) + 2 02(8) T’ 2 N02(g) given S°(N2(g))=191.5 J/K-mol ' S°(02(g))=205.0 J/K-mol S°(N02(g))=240.0 J/K-mol -156.5 J/K -121.5 J/K +155 J/K +6365 J/K -3l3.0 J/K ween? 10. 11. 12. 13. 111.009”? For the reaction 3 C2H2(g) -> C6H6(l) AG°=-503 M, the eqnilibrium constant K at 25°C is: A. 4.93><10‘3 B. 1.48X10“ C. 5.71><10‘° D. 6.74><10'$9 E. 1.23 Consider the reaction: ‘ N2(g) + 3 F2(g) —+ 2 NF3(g) AH°=-249 1d and A °=-278 J/K Calculate AG° at 500K and state whether the equilibrium composition should favor reactants or products at 500 K. A. -110 kJ; reactants are favored B. +1 .39>< 105 kJ; reactants are favored C. -3 88 kJ; products are favored D. -110 kJ; products are faVOred E. ~139 kJ; products are favored Consider the reaction: - SiC14(g) + 2 Mg(s) -' 2 MgClz(s) + Si(s) Calculate AG° at 25°C given the values below: AGf°(SiCl4(g))=-620. kJ/mol AGr°(MgC12(s))=-592. kJ/mol A. -564 k] B. +28 kJ C. +385 k] D. -1212 k] E. . -28 kJ At 2600 K, AG°=+775 1:1 for the reaction below: ‘ B4C(s) *" 413(8) + C(S) If the partial pressure of the gaseous boron B(g) is 1.0x10'5 atin over a mixture of the two solids, AG at 2600 K is and the reaction is in the forward direction. -220. 1d; spontaneous . -270 kJ; spontaneous -220 kJ; nonspontaneous +114 kJ; spontaneous +746 kJ; nonspontaneous A galvanic cell A. uses electrical energy to drive a nonspontaneous chemical reaction. B. does not involve a redox reaction. C. has E°ceu=0 D. ' converts chemical energy of a spontaneous chemical reaction into electricity. E. has E°ceu< O. ' The net cell reaction for a galvanic cell is: Fe(s) + Ni*2(aq) —* Fe*2(aq) + Ni(s) The shorthand notation for this cell is: Fe(s)lNi*2(aq)llFe*2(aq)lNi(s) Fe(s)|Fe*2(aq)llNi*2(aq)lNi(s) Ni(s)lFe*2(aq)lINi*2(aq)lFe(s) Ni(s)lNi*2(aq)|lFe*2(aq)FFe(s) Fe(s)lNi(s)|INi*2(aq)lFe*2(aq) 91.5.09"? Determine the standard net cell potential E°cen for the following net cell reaction 3 Cr+3 + Al -+ 3 Cr+2 + Al+3 E°ceu= ? given ' Cr+3 + 1c“ -* Cr+2 °= -O.41 V Al+3 + 3e‘ —+ Al °= -1.66 V -2.07 V +1.25 V -0.43 V +0.43 V +0.14 V FUDGE”? The standard net cell potential E°ceu for the reaction below is +0.19 V. Ni+2 + Fe(s) ,-> Fe” + Ni(s) Ea," = +0.19 v . The standard Gibbs free energy AG° (in units of kJ) for this reaction is: -37 U -254 kJ +18 k] -73 k] -18 kJ econ? 18. 19. 20. 21. 22. Which of the following conditions does NOT specify a spontaneous reaction in the forward direction? 'A. AStotal < O B. Q < K C- Eocell > 0 D. AG° < 0 E. All of the above specify nonspontaneous reactions. Which of the following acts as a weak electrolyte when dissolved in water? The conjugate base of HCO3' is mcow> C121'12201 1(5ugar) KOH HNO3 HC2H302 KBr while the conjugate acid of H20 is from the HCl will neutralize the The pH of a buffer containing 1.5 M HN02 and 0.50 M NaNO2 is: A. H2C03; OH' B. OH‘; H3O+ C. CO3'2; H3O+ D. C02; H” E. None of the above is correct. When HCl is added to a HF/NaF buffer the of the buffer. A. H3O”; HF B. Cl'; Na“ C. CH; HF D. H302 OR B. H3O*; F' KA(HNOZ)=4.6X10" A. 3.34 B. 11.14 C. 1.76 D. 3.90 E. 2.86 23. 24. 25. 26. 27. Which of the indicators below should be used to detect the endpoint in a titration of HC2H3O2 with NaOH? A. Methyl green 0.2-1.8 yellow to blue B. Ethyl red 4.0-5.8 colorless to red C. Bromothymol blue 6.0-7.6 yellow to blue D. Thymol blue 8.2-9.8 colorless to red E. Any of the indicators in A-D will do. Which one of the following dissolves in water to give a neutral solution? Addition of which of the following to an aqueous solution saturated with AgZSO4 wpow> AlCl3 NaClO4 NaOH NH4Br NaC2H3O2 (Ksp= 1.19x10") will increase the Solubility of the AgZSO4? A. B. C. D. E. HCl NaZSO4 AgNO; NH3 All will increase the solubility of Ag2804. The molar solubility of Ag3PO4 in pure water is: Ksp(Ag3PO4)= 1.05><10“‘ wpow> The only factor which will change the value of the equilibrium constant K is: P1909“? 1.97><10‘9 M 3.89X107” M 1.05X10“° M . 2.86X10'° M 4.44X10'5 M an increase in product concentrations. a decrease in reactant concentrations. An increase or decrease in volume. an increase or decrease in temperature. the addition of a catalyst. 28. 29. 30. 31. 32. The equilibrium constant expression for the decomposition of barium nitrate by the reaction below is: 2 Ba(N03)2(s) H 4 N02(g) + 2 3510(5) + 02(g) K={ [NOz]4x [Baoizx [02] }/[Ba(1‘103)2]2 K={ [NOz]4x [02]} K=[Baa‘103)2]2/{[Nozl‘x[13210]2 X [02]} K=1/{ 9102144021} K={4>< [N02] x [02]} - mace? Which one of the following aqueous solutions will have the lowest freezing point? A. 0.25 m AlBr3 B. 0.25 m NaBr C. 0.25 m C12H220“(sugar) D. 0.25 m HF ’ E. 0.25 m CaBrz Consider the reaction below at equilibrium. '2 BrCl(g) <-> Br2(g) + Clz(g) AH=+20. kJ Which of the following stresses applied to a mixture of the three gases at equilibrium will cause the formation of more C12? Increase the pressure by reducing the volume. Add a catalyst. Raise the temperature. Remove half of the gaseous BrCl. Add more gaseous Brz. WDOP’? Silver forms a soluble complex ion [Ag(SZO3)2]'3 with K52.9x10 .‘3 The equilibrium concentration of Ag” in a 0.20 M solution of [Ag(8203)2]'3 is: Ag*(aQ) + 2 3203'2(aCI) H[138(3203)2]'3(aq) KFZ-9X10” A. 1.7x10"5M B. 3.4x10'”M ' c. 1.2x10'5M D. l.7><10'”M E. , 0.20M Geometric isomers are possible for which of the following: (where M=central metal cation and X, Y designate different ligands) A. MXZY2 (tetrahedral) B. MX3Y (square planar) C. MXZY2 (square planar) D. MX..Y2 (octahedral) E. Geometric isomers are possible for C and D. F5 36. Use crystal field theory to decide how many unpaired electrons in the metal 3d orbitals for the octahedral complexes below. [I EH 1.: [I 1“ (CM) 1.3 A. four two B. three three C. five one D. two four E. two . two Consider the reaction and rate law below (CH3)3CBr + OH‘ -* (CH3)3COH + Br‘ Rate = k[(CI-I3)3CBr] ‘ . Which of the following will NOT increase the rate of reaction? Increase the reaction temperature. Add a positive catalyst for the forward reaction. Increase the concentration of (CH3)3CBr. Increase the concentration of OH‘ All of the above. P1909”? A12(SO4)3 is dissolved in water such that the concentratiOn of SQ;2 is 0.20 M. What is the concentration of Al”? A. 0.067 M B. 0.13 M C. 0.60 M D. 0.30 M E. 0.39 M In the qualitative analysis scheme, initial separation of the metal cations into Groups I-V is based on differences in acid/base properties of the metal cations. amphoteric properties. differences in Ksp values. ability to form ammonia complexes. hydrolysis of the metal cations. P190533? 37. 38. 39. 40. m60w> Determine the rate law for the reaction below 52(3{2(aQ) ‘+ 3 I“(81(1) '* 2 S()iz(aq) + 1§(aq) given the initial rate data m tszosfl In l 0.10 0.10 3.60><10'3 2 0.20 0.10 7.20><10'3 3 0.10 0.30 10.8><10‘3 Rate = k[8203'2][1']3 Rate = k[szo.;2][1-]5 Rate = k[8203'2] [I‘]2 Rate = k[8208‘2]2[1'] Rate = 1([8208‘2] [I'] WUOF’?’ A three step mechanism has been suggested for formation of COClz: 1: c12 —» 2 (:1 (fast) 2: c1+ co —> COCl (fast) 3: COCl + c12 —» cool2 + c1 The intermediate is 18 (slow) COCl; bimolecular CO; unimolecular COClz; bimolecular C12; bimolecular COCl; unimolecular FUDGE”? Calculate Kc for the reaction below: ' 2N0@)+ 0x9 H'ZNOAQ K5? At Eq: 0.200M 0.100M 0.250M A 0.0800 B. 0.0641 C. 12.5 D 15.6 E 3.95 I Consider the equilibrium below 2302(g) + 02'(g) <—> 2803(g) Kc=5.00at1300K If the initial concentrations are: [SOz]i=1.20 M, [Oz]i=0.45 M, and [SO3]i=2.10 M, the reaction will: be at equilibrium. shift to the left to reach equilibrium. 'shift to the right to reach equilibrium. not shift at all unless the temperature is increased. None of the above. _/ Ha - and the molecularity of the rate determining step 41.. 42. 43. 44. Para-aminobenzoic acid (PABA; a weak acid with KA=2.2><10‘5) is used in some sunscreens and hair conditioning products. The acid equilibrium can be represented as below (HA represents PABA): HA(aQ) + H20 H Mac!) + H30*(aQ) The pH of a 0.10 M solution of PABA is: KA=2.2x10‘5 A. 2.83 B. 5.69 C. 6.91 D. 11.17 E. 3.78 Which of the following is- NOT a Lewis base? A. H20 B.- NH3 C. K: D. c1- E. 0H- Which of the following is a buffer? 0.5 M HC1/0.1 M NaCl 0.5 M NaOH/0.1 M NaCl 0.5 M NH3/0.1 M NaOH 0.5 M Hc102/0.1 M Nacro2 0.5 M HC102/0.5 M NaOH mpowe 25.0 mL of 0.100 M HNO3 is titrated with 0.150 M NaOH. What is the pH of the solution after the addition of 12.0 mL of NaOH? 0.15 1.72 A. B. C. 2.51 D. 12.28 E. 7.00 45. 46. 47. 48. A solution is 0.010 M in Mn”, Zn”, Pb” and Cu” and 0.010 M in HZS at a pH=0.50. Calculate the ion product. Which metal cations will precipitate as the sulfide? MS(S) + 2H30+(3CI) H M”(aQ) + H25(aQ) + 2 H20 Km KspA MnS 3 X 1016 ZnS 3 X 10‘2 PbS . 3 X 10‘7 CuS 6X10"6 A. Mn” B. Cu"2 1 C. Pb” and Cu” D. Zn”, Pb” and Cu” B. All will precipitate. 10.0 mL of 0.20 M HC2H302 is titrated with 0.15 M NaOH. The volume of base needed to reach the equivalence point is . A. 7.5 mL B. 13 mL C. 3.0 mL D. 10. mL E. 30. mL Consider the titration in the last question. If the concentration of NaC2H302 at the equivalence point is 0.086 M, the pH at the equivalence point is: (KA(HC2H3OZ)=1.8><10’5) ‘ A. 6.90 B. 10.03 C. 5.26 D. . 9.63 E. 8.84 A 1.138 g sample of naproxen (an anti-inflammatory agent) is dissolved in 0.0297 L of benzene solution. The osmotic pressure. of the resulting solution is 4.00 atm at 20°C. The molar mass of naproxen is: A. 176 g/mol B. 307. g/mol C. 3.80X105 g/mol D. 230. g/mol E. None of the above. 49. 50. The standard net cell potential E2“, is -0.40 V for the cell specified below. Pt(s)|H2(g, 2.0 atm)lH?*(aq, 0.0050 M)||~Cd*2(0.50 M)|Cd(s) The net cell potential Ecell under the nonstandard conditions specified above is: (HINT: Write the net cell reaction first) A. -0.60 V B. +0.36 V C. -0.26 V D. +0.54 V E. -0.35 V Mark the same answer as Question #49. This means that Question#49 is worth double. » .64c/fi57t743m521mrr1 l/Wy/ (M677 0101 9* W A“ 013 0% (416° we a ‘ (/3 0‘ ol‘7/66 302i" 050: W 6. 7/4“ 5106‘ '75 Co 50‘ ‘27 D W 6 (9/116 01? f5 (/7 t 7 6‘ 91.7 fie W06 8705 90 C W (1 90‘ d/E 5D C my 0026' HIM a \00 fl 1 I/ 134‘ K” /‘/D\ . ; // [56° 37 g: l/ /74' 3? 0‘ if”. yofio 3) [70° fl? MG ,3: ...
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This note was uploaded on 04/26/2008 for the course CHEM 116 taught by Professor Chigwada during the Summer '07 term at WVU.

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16-final_exam - CHEMISTRY 16 FINAL EXAM Dr. M....

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