University:
Concordia University Wisconsin
Course:
CHEM 1414 | General Chemistry I
Academic year:

2021
Views:

361

Pages:

7
Author:

Accinkiquicpqw

PART A: MULTIPLE CHOICE 3. Consider tire following reaction; Zn,., + 2HC1¦M ' INSTRUCTIONS: For each question, select tbe best answer and record your choice on die Response Form proi'ided. Using an IIB pencil, compiclely fill in the circle thai has the letter corresponding to your answer. 1. Which of the following reactions will be slowest at 250C? -'zlo,) -r nJ(S) A graph of concentration of HO vs lime could be represented by [HCll EHO] [HC1] Ehci] A. Cu(j| + S(J, -> CuS(j) B. H*,..., + OH",.., ¦ M ^ H,0„ C. Pb2;.., , -» PbCl -'aW '(»») + 2Cr,(»«) D. 2NaOCl, , -»2NaCI,. 2. Which of the following could be used as tire units for rate of a reaciion? i. mL/s II. g/rmn III. M/mjn 4. Consider tbe following experiments, each involving equal Fxpcrimcnt Experiment I II of zinc and fO.OmL of acid: Experiment III A. 1 only. 13. I and U only. C. II and HI only. D. 1,11 and m. Zn cube 1.0 MHO Zn cube Zn powder 0.5 MHO 1.0MHC1 The tale of leactiun in order fronr fastest to slowest i: A. I > IT >111 B. II > I >111 C. Ill > I > 11 D. Ill > II > I 5. What happens to the energy of reactant molecules as they approach one another? Potential Energy Kinetic Energy increases increases increases decreases decreases increases decreases decreases 8. In which of the following do both favour tbe reactants? enthalpy and entropy factors -w. ^2w «_ v.i2(o?j AH = —25kJ B. C,., + H.O,,, 7± CO,., H (s)+ 2(1) C. SCO^) + SHjO, AH = +131kJ D. Na2COM + HCIta) ^ 2NaClM + C02W + H20, -'(') AH = -28kJ AH = +1239kJ 9. Consider the following equilibrium: 6. Consider the following reaction mechanism: H,,., + L,., 7Z 2HI,, Step 1 CICT + H20 -> HCIO + OH" Step 2 r + hcio -»mo + cr Step 3 HIO H OH" -»10" -f H20 The catalyst i Which graph represents what hap]>ens wbcu some HI is removed and a new equilibrium i established? [HI] [HI] A. ICT B. HjO C. CICT D. ClOH 7. Consider the following equilibrium; [HI] 2NOCIw ,-t 2NO(s)+CI!(8) A flask of fixed volume is initially filled with NOCl(8), NO|£( and Oj^. When equilibrium is reached, the pressure lias increased. To reach equilibrium, the reaction proceeded to the A. left because Trial was less than K^. B. right because Trial was less than K^. C. left because Trial was grcalcr than K^. D. right because Trinl was greater than K^. 10. Consider the following equilibrium: '-u(.,) + "2U(8) < Wlml will cause a shift in the equilibrium? A. adding a catalyst B. changing volume C. adding an inert gas D. changing temperature -3- •4- 11. The equililiruim expression for a reaction is K., = 14. A saturated solulionof NaCl coatains 36.5 g of solute in 0.100L of solution. The solubility of the compound is fwi4 A. 0.062 M B. 1.60 M C. 3.65 M D. 6.24 M " KfM3 The reaction could be A. 6irM+BiS(s) 2 20^,+3^ R. fiHVrt + RiAoi ^ 15. Calculate the [Li''] in 200.0mL of 1 5M Li2SO^ C. 2Bi3N)+3HiSM ^ Bi^,,+CH'H| A. 0.30 M B. 0.60 M C. 1.5 M D. 3.0 M D. 2Bi3;..1 + 311,3,.., ll + OH4,W) 1 ta) IX Consider the following equilibrium: ^ CoCl/^, CO(H20)62^ (pink) 16. When equal volumes of 0.20 M RbCl and 0.20 M SrS are combined, (blue) When Lite temj)erature is increased, the solution lunts a dark blue. Based on Ihis observation, the reaction is A, exoihemtic and Utc KC43' What is ibe conccntralion of O3 when the equilibrium concentration of 02 is 6.0 x 10"2 mol/L? A. 2.4 x 10~3 mol/L B. 4.0 x 10"2 mol/L C. 6.0 X 10"2 mol/L D. 9.0 X 10"2 mol/L 22. Aqua regia is a conceutrated aqueous solution of HC1 and HNO,. The strongest acid t aqua regia is The K_ expression for a saturated solution of Mg(OH)2 A. HCl B. HjO C. H304 D. HNO, ' ' [Mg(OH)j ] B. K!p=[Mg24 ][OH-f C. KJJ, = [Mg2*|OH-] 23, The predominant acid-base reaction between H202 and H20 is D. Klp=[Mg^|20R-f A. Hj02 + H20 ^ 30H" + H4 B. H202 + H20 ^ 2H;0 + O2" 19. Consider the following saturated solutions: C. Hj02 + H20 -> HjOj4 + OH" CUSO4, BaS04> CaS04 D. Hj02 + HjO -» H3O4 + H02" The order of cation coDCentralion, from highesl lo lou'est, is A. [Ba2*] > [Ca24] > [Cu2*] 24. Which of Uic following reactions favours the formation of products? B. [Ca24] > [Cu2+] > [Ba24] A. HN02 + r HF + NOj" C. [Cu24]>[Ca24]>[Ba24j B. HjCOJ + lO," ft HIOj 1- HCO," D. [Cu24]>[Ba24j>[Ca24] C. Nn44 + Cj042" ft HCjOJ" + NH, D. HCN + HCOO" ft HCOOH + CN" 20. When 1.0 X 10"3 moles of CuCI;^ are added to 1.0L of 1.0 x 10"3 M 10,", the A. Trial Kjj, > Kjy and a precipilate forms. B. Trial Kjp < Kjp and a precipitate fomts. C. Trial > Ky and no precipilate forms. D. Trial and no precipitate forms. 25. Which of the following 1.0M soltitious will have the lowest [h3o4] ? A. B. C. D. H2S UNO, HjCO, CH3COOH 21. The conjugale base of H2P04~ is A. OH" B. TO^" c. H3P04 D. I-1P042' -7- OVER -8- 26. In a solution of 0.10M NaCN, the order of ion coDcenlialioii, from highest to lowest, is 30. When comparing 1.0M solutions of bases, the base with the lowest |OH ] is the A. [Na*] > [OH~] > [CN"] > [HaO"*] A. weakest base and it has the largest K6 value. B. strongest base and it has the largest K^value. C. weakest tsise and it has the smallest Kb \ alae D. strongest base and it has the smallest Kj, value. B. [Ha'1] > [CN"] > [OH"] > C. [HjC] > [OH"] > [CN~] > [f''a+] D. [OH"] > [N'S"'] > [CN"] > j 31. The value of K6 for HCjO^ 27. What will cause the value of K„ to cliange? A. B. C. D. A. g C. D. adding OH adding a catalyst decreasing the pH increasing the lempetalure 28. What is the concentration of Sr(OH)2 in a solution with a pH - 11.00? 1.7 xlO"13 1.6 X lO"10 6.4 X 10"s 5.9 X 10"J 32. Wtiichof the following applies at the transition point for all indicators, Hind? A. 2.0 X lO-11 M B. 1.0 x 10"" M C. 5.0 x 10'J M D. 1.0 xlO"3 M A. [HInd] = [lnd-] B. j^lnd"] = [lljO*] C. [HjO* j = [oh- ] D. [Hind] = [HjO*] 29. The K0 expression for HTe 33. Identify the indicatorlhat has a K0 of 1.6 x lO-7 ? A. K..!Si5fe2l A. mctJiyl red B. Ihymol blue C. pheDolphlhakin D. bromihyrnol blue [HTe"] [HTe-llIjO4] •= [H2Te] iHTe-lOH-] 34. Which of the following acid solutions would require the smallest volume to completely neutralize lO.OOmL of 0.100M NaOH 1 A. O.JOOMHCl B. 0.100 M HjPOa C. 0.100MH2C204 D. 0.100 M CHjCOOH 35. What is the pH of the solution formed when O.OWmol NaOH , is added to TOOL of 0.050M HCI ? A. 1.30 B. 1.40 C. 2.00 D. 7.00 36. Which of die following titrations will have an equivalence point with a pH less than 7.00? A. H2S04 with NHj B. HN03 with LiOH C. HjPOj with KOH D. 11COOH with NaOH 37. Which of the foil owing graphs describes the relationship between pH of a buffer solution and < volume of HQ added to the buffer? pli pH Volume of HCI added Volume of 1IQ added pH pH Volume of HCI added Volume of HCI added -11 - OVER PAKTB: WRFITEN RESPONSE 2. Consider the observations for the following equilibrium: N=0%) £ 2N0,(S) INSTRUCTIONS! You will be expected to commumcate your knowledge and UDden;landing of chemical principles in a clear and logical manner. Your sleps and assumplious lending lo n solulion musl be n riflen in the spaces below lie questions. Answers must include units where appropriate and be given lo the correct number of significant figures. For questions involving calculation, full marks will NOT be given for providing only (colourless) (brown) Trial Temperature °C Colour I. 10 lighl brown II. 50 dark brown a) Sketch the potential energy < 1. a) Complete the sleps in the foliowing mechanism i the graph below for this equilibrium. (H marks) progress of the reaction 0,11 -» O, + 11 b) Explain the colour change using l.e ChStclier's Principle 2NO -v N, I- O, (1 mark) b) Dcfiue tbc tcun leiiciion miamediate and give an example from the completed mechanism above. 11 f- marks) c) Other than changing temperature, whal could be done lo < i shift to the left? (11 Example: 3. Consider the data obtained for the following equilibrium: Fe3* , + SCN", [Fe5i] [schr] [FeSCN21] Experiment 1 3.91 X 10"2 8.02 X 10""5 9.22 x 10"^ Experiment 2 6.27 x 10"' 3.65 x lO"1 ? Calculate tire FeSCN I in experiment #2. 4. At 25''C, will a precipitate form when 25.0 mL of 0.010 M Pb(N03); is combined with 75.0mL of 0.010M Nal? Support your answer with calculations. (3 marks) r» KeSCN2;. (09) (3 marks) -18- - 19- OVER 5. When HCl is added loo saiornled solnlionof CviC,04, some precipilale dissolves. However, when HQ is added to a saturated solution of PbG2, additional precipitate forms. CUCjOJ PbCI2 Explain these observations. Support your explanation with chemical equations. (3 marks) 7. Consider the salt amrnouinai acetate, NH^CHjCOO. a) Writetheequalionforlhedissocialionof NH4CH3COO (1 mark) b) Write equations for the hydrolysis reactions which occur. (2 marks) c) Explain why a solution of NH4CH3COO has a pH = 7.CO. Support your answer with calculations. (2 marks) -22- A 0.100M solution of an unknown weak acid, HX.hasa pH = J.4I4. What is the K„ forHX? (4 marks) Answer Key PARTE: WRITTEN RESPONSE 2. Consider the observations for the following equilibrium: Value: 32 marks Suggested Time: 5U minutes (colourless) (brown) INSTRUCTIONS: You will be expected to communicate your knowledge and understanding of chemical principles in a dear and logical manner. Your steps and assumptions leading to a solution must be written in the spaces below the questions. Answers must include units wbere appropriate and be given to the correct number of significant figures. For questions involving calculation, full marks will NOT be given for providing only an answer. Trial T emperature °C Colour I. 10 light brown IL 50 dark brown a) Sketch the potential energy curve on the graph below for this equilibrium. (Imark) 1. a) Complete the steps in the following mechanism- (lA marks) Solution: Solution: For Example: NO + Pt -> NOPt Step 1 e-A-mark progress of the reaction Step 2 NOPt + NO -» N2 + 02Pt StepS OjPt -» Oj + Pt Overail 2NO N2 + 02 b) Explain the colour change using Le ChStelier's Principle. (I mark) Solution: For Example: b) Define the term reaction intermediate and give an example from the completed mechanism above. (1A marks) An increase in temperature causes the reaction to shift to the rightandthe (NOj| increases. c) Other than changing temperature, what could be done to cause a shift to the left? (I mark) Solution: Solution: For Example: For Example: Definition: A substance which forms in one step of a mechanism and is used up in a later step. «-l mark Example: NOPt or 02Pl <- imark To cause a shift to the left add N02 or remove Nj04 or decrease the volume. 3. Consider the data obtained for the following equilibrium: 4. At 250C, will a precipitate form when 25.0mL of 0.010M Pb(N03)2 is combined with 75.0 mL of O.OIOM Nal? Support your answer with calculations. (3 marks) Fe9? + SCN",2± FeSCN2; [SCN~] Solution: [FeSCN2'] For Example: Experiment I 3.91 x 10"2 8.02 x 10"s 9.22 x lO"1 Experiment 2 6.27 x 10"3 3.65 x lO"1 ? Pbi2M tX Ptf&d + a-M (3marks) CalcuJatetbe [FeSCN j in experiments. [PbMl = 0.010M x-j^2k = o.00250M t J 100.0100.0 mL mL [r] = 0.010MxT§^ = 0.00750M Solution: I FeSCN2 Trial K^Pb-frf K. = (O.C02SO)(0.00750)2 (3.91 x 10" <-1t mark = 2.94 x 10' (6.27 x tO'^S.SS X 10" [FeSCN2"] = x = 6.73 X lO^M (Deduct i mark for incorrect significant figures.] = 1.4 X 10"' Since Trial (l.4 X 10"') > Kv(8.5 x 10"9) a precipitate does form. } >-1 mark 1^ mark 5. When HQ is added to a saunated solution of OiC204, some precipitate dissolves. However, when HQ is added to a saturated solution of PbClj, additional precipitate forms. 6. A 0.100M solution of an unknown weak acid, HX, has a pH = 1.414. What is the K, forHX? (4 marks) Solutions For Example: ^O*] = 0.CB855M HX + H20 [I) £c] [E] H3O* + X" 0.100 0 0 -0.03855 +0.03855 +0.03855 0.061 0.03855 0.03855 Explain these observations. Support your explanation with chemical equations. (3 marks) K Solution: For Example: K CuCjO.,^, £ Cu'*,, + f-lmark H* from the acid reacts with the C^O.,2- to form HC204~ reducing the [CjO^2"! and causing a shift to the product pxj (Q.C6 855X0-03855) 0.051 = 0.024 ^Deduct ^ mark for incorrect significant figures, j ^ mark The common ion effect causes a shift to the rishu 1 mark 1. 3. D C 4. C 2. 7. Consider the salt ammonium acetate, nh4ch3coo. a) Write the equation for the dissociation of nh4ch3coo. (1 mark) 12. B B B C B D C C 13. A 5. Solution: 6. NH4CH3COO(S) ^ NH/W) + CH3COO-(ll9) 7. 8. b) Write equations for the hydrolysis reactions which occur. (2 marks) 9. 10. Soiutioti: 11. NH/ + HjO HsO* + NH3 and CHjCOCT + HjO CH3COOH + OH" c) Explain why a solution of NH4CH3COO has a pH = 7.00. Support your answer with calculations. 26. B 27. D C B C 28. 29. ¦30. 33. 17. A A A A D 34. B 18. B 35. C 19. C 36. A 20. 37. B 23. D D C D 24. A (2 marks) 16. 1.8 X 10"5 the acidic cation is completely neutralized by the basic ; A 31. Solution: the K0 for NH4* = Ki, for ch3coo" 25. D D 14. 15. K, for NH/ = 5.6 x 10"'° A 21. 22. 32.

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