142C142_Final_Trial_Au-07

142C142_Final_Trial_Au-07 - Chemistry 142 A Name Section...

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Unformatted text preview: Chemistry 142 A Name Section No. Final Trial, Autumn 2007 J. B. Callis, Instructor Rules for this exam: 1. Do not open this exam book until told to do so by the instructor. 2. Sit in your assigned seat. You must remain in your seat until the g end of the exam. If you finish early, you may not leave or take a book out. 3. This is a closed book exam. 4. Circle the one correct answer. 5. You may use a calculator, but not a PDA or laptop. You may not have a connection open to the internet or to a phone. 6. You may not have any extra sheets of paper out. 7. Place all books, packs, purses, etc. underneath your seat. 8. Be sure to put your name on every sheet of paper. You will not be permitted to do this after the exam ends. 2 i i E z 5 i s I I i i i i l . g i 9. This exam ends promptly at the end of the class period. Please put down your pencil when the bell rings and pass your exam to the outside isle. 10. This trial exam has 22 questions limited to Ch 6—8. All count equally. A periodic table and 2 blank sheets will be attached to the final exam. 11. Do not talk to any other student for any reason. If you have a question, raise your hand and a TA will come to you. Please sign below to indicate that you understand these rules and that you arrived at your answers without help. Signed Date For the reaction j A + k B = 1 c + m D, Kp = KC(RT)A“ Where An is the sum of coefficients of the gaseous products minus the sum of coefficients of the gaseous reactants. — b V b2 — 4 The roots of a quadratic: ————2——CZ£ ; PV = nRT a pH = -10g10([H+]) = -10g10([OH-]); P1V1/T1 = P2V2/T2 pH = pKd Hog [base] ; effusion rate gas 1 2 fl mm = ’3RT [aCId] effusron rate gas 2 M1 M R = .08206 L atm/(mol K)= 8.3145 J K" mol; T(K)=T(°C)+273.15 1 atm = 760 torr = 101.35 kPa; NA = 6.022 x1023 l+ FrontPage 2" l g i 2 l l E 3 i Chem 142 B Name See. No. Final Trial, Au—07 J. B. Callis, Instructor 1. Indicate the mass action expression for the following reaction: 2X(g) + Y(%) ‘—- 3W(g) + V(g) . A X 2 Y w 3 V B MED/l [c] [33171le [D] E13le [ZXHYl [Wl3lVl ' 2_ For the reaction 2H2(g) + 02(g) # 2H20(g), what is the relationship between K and KP at temperature T? [A] K = Kp(RT) [B] Kp = K(RT)2 [C] Kp = K(RT) [D] K: Kp [E] K=Kp(RT)2 Chem 142 B Name Sec. No. Final Trial, Au—07 J. B. Callis, Instructor 3. Consider the following equilibrium: H2(g)+12(s) ‘——"‘“ 2H1(g) AH= +68.0 kJ/mol (endothermic) Which of the following statements about the equilibrium is false? [A] This is a heterogeneous equilibrium. [B] If the pressure on the system is increased by changing the volume, the left side is favored. - S [C] Removing HI as it forms forces the equilibrium to the right. [D] If the system is heated, the right side is favored. [E] Adding more H2(g) increases the equilibrium constant. 4. The following reaction is investigated (assume an ideal gas mixture): 2NzO(g) +N2H4(g) : 3N2(%) + 2H20(g) Initially there are 0.10 moles of N20 and 0.25 moles of N2H4, in a 10.0-L container. If there i are 0.06 moles of N20 at equilibrium, how many moles of N2 are present at equilibrium? [A] 0.9 [B] 0.06 [C] 0.04 [D] 0.02 [E] none of these Chem 142 B Name Sec. No. Final Trial, Au—07 J. B. Callis, Instructor 5. Consider the following reaction: 2HF(g) ;‘ H.2(g) + F2(g) (K = 1.00 x 10—2) Given 1.00 mole of HF(g), 0.500 mole of H2(g), and 0.750 mole of F2(g) are mixed in a 5.00-L flask, determine the reaction quotient, Q, and the net direction to achieve equilibrium. [A] Q = 0.150; the equilibrium shifts to the right. I [B] Q = 0.375; the equilibrium shifts to the left. [C] Q = 0.375; the equilibrium shifts to the right. ' [D] Q = 0.150; the equilibrium shifts to the left. ; [E] Q = 0.150; the system is at equilibrium. 6. Consider the following equilibrium: N2(g) + 3Hz(g) ‘7‘— 2NH3(g) l with K = 2.3 x 10—6, 1.00 mole of all reactants and products are placed in a 1.00-L container. Calculate the equilibrium concentration of N2. [A] 0.5 M [B] 2.0 M [C] 1.0 M [D] 1.5 M [E] 2.5 M l l i. l l l l .1 i l Chem 142 B Name Sec. No. Final Trial, Au-O7 J. B. Callis, Instructor 7. Given the equation 2A(g) ;‘ 23(g) + C(g). At a particular temperature, K = 1.6 x 104. If you start with 2.0 M of chemical A, calculate the equilibrium concentration of chemical C. p [A] 2.0 M [B] 8.3 x 10*3 M [C] 0.99 M [D] 6.25 x 10‘5 M [E] none of these 8. Which of the following does not represent a conjugate acid-base pair? [A] HCN and NH3 [B] HF and F" [C] C5H5NH+ and C5H5N [D] H3OJr and H20 [E] none of these 9. A monoprotic weak acid when dissolved in water is 0.92% dissociated and produces a solution with pH = 3.42. Calculate Ka of the acid. [A] 3.5 x 10-6 [B] 1.4 x 10-7 [C] 2.8 x 10-3 [D] need to know the initial concentration of the acid [E] none of these Chem 142 B Name See. No. Final Trial, Au—O7 J. B. Callis, Instructor 10. Calculate the pH of a solution that is 7.22 x 10‘4 M C6H5NH2. Kb is 3.8 x 10‘10. [A] 7.72 [B] 7.50 [C] 6.50 [D] 6.28 [E] none ofthese 11. Which of the following aqueous solutions will have the highest pH? For NH3, Kb = 1.8 x 10’s; for C2H302—, Kb 2 X [A] 2.0 M HCl [B] 2.0 M NaOH [C] 2.0 M NH3 [D] 2.0 M HC2H302 [E] all the same i l r i l I [ l E l l l g i l. x i l 1 x l s '1 l. i l 12. HOAc: Ka =1.8 x 10-5 H2C03: Ka1= 4.3 x 10-7 Ka2 = 5.6 x 10-11 Which of the following 0.01 M solutions has the highest pH? [A] Na2C03 [B] HOAc [C] NaHCO3 [D] NaOAc [E] HZCO3 Chem 142 B Name See. No. Final Trial, Au-07 J. B. Callis, Instructor 13. If the following substance is dissolved in pure water, will the solution be acidic, neutral, or basic? a) acidic b) neutral 0) basic solid potassium chloride (KCl) 14. Calculate the pH of a solution made by a mixture of the following acids: 0.40 M HC2H302 (Ka = 1.8 x 10—5), 0.10 M HOCl (Ka = 3.5 x 10-8), and 0.20 M HCN (Ka = 6.2 x 10-10). [A] 3.49 [B] 2.57 [C] 4.95 [D] 4.23 [E] 3.92 15. Calculate the pH of a solution that contains 325 M HCN (Ka = 6.2 x 10-10), 1.00 M NaOH and 1.50 M NaCN. [A] 9.25 [B] 7.46 v [C] 8.28 [D] 8.86 [E] none ofthese Chem 142 B Name Sec. No. Final Trial, Au-O7 J. B. Callis, Instructor 16. What is the molarity of a sodium hydroxide solution if 25.0 mL of this solution reacts exactly with 22.30 mL of 0.253 M sulfiu'ic acid? [A] 0.284M [B] 0.113M [C] 0.567M [D] 0.226M [E] 0.451 M 17. A solution contains 10. mmol of H3PO4 and 5.0 mmol of NaH2P04. How many milliliters of 0.10 M NaOH must be added to reach the second equivalence point of the titration of the H3PO4 with NaOH? [A] 2.0><102 [B] 150 [C] 50 [D] 1.0><102 [E] 250 18. In the titration of a weak acid HA with 0.100 M NaOH, the stoichiometric point is known to occur at a pH value of approximately 11. Which of the following indicators would be best to use to mark the endpoint of this titration? [A] an indicator with Ka =10—10 [B] an indicator with Ka =1o—14 [C] an indicator with Ka = 10‘8 [D] an indicator with Ka = 10‘11 [B] an indicator with Ka = 10~12 Chem 142 B Name Sec. No. Final Trial, Au-07 J. B. Callis, Instructor 19. A 100.0 mL sample of the weak acid H3A (0.100 M) titrated with 0.200 M NaOH. What are the major species at the following point in the titration (water is always assumed to be a major species). After 0 mL of 0.200 M NaOH is added. [A] H3A, H215: [B] H3A [C] HZA: HA2- [D] H3A, HZA: HAZ‘, A3" [E] HZA' 20. It is observed that 7.5 mmol of BaF2 will dissolve in 1.0 L of water. Use these data to calculate the values of Ksp for barium fluoride. [A] 1.7x 10—6 [B] 4.2x 10—7 [C] 2.1 x 10—12 [D] 5.6><10—5 [E] 7.5 ><10‘3 21. The solubility of La(IO3)3 in a 0.10 M K103 solution is 1.0 x 10*7 mol/L. Calculate the Ksp for La(IO3)3. [A] 1.0 x 10—8 [B] 1.0 x 10-10 [C] 2.7 x 10-9 [D] 2.7 x 10‘27 [E] none of these Chem 142 B Name Sec. No. Final Trial, Au-07 22. The following three equations represent equilibria that lie far to the right. HNO3(aq) + CN‘(aq) : HCN(aq) + NO3‘(aq) 'H'CN(aq) + OH—(aq) =2 H200) + CN—(aq) H200) + CH3O—(aq) # CHZOH(aq) + OH'(aq) Identify the strongest acid. [A] HCN [B] CH3OH [C] H20 [D] OH— J. B. Callis, Instructor [E] HNO3 ...
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This note was uploaded on 05/17/2008 for the course CHEM 142 taught by Professor Zoller,williamh during the Spring '07 term at University of Washington.

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142C142_Final_Trial_Au-07 - Chemistry 142 A Name Section...

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