CHM 2046 Practice Final Exam

Size: px

Start display at page:

Download "CHM 2046 Practice Final Exam"

Teresa Webster
6 years ago
Views:

1 CHM 2046 Practice Final Exam IMPORTANT: Bubble in A, B or C as the test form code at the top right of your answer sheet AND also bubble in your Section Number and UFID on the left side of your answer sheet. VERSION 0 1. The reaction A + 2B 2C has K c = 200 at a particular temperature. At a particular moment in time, [A] = 0.50 M, [B] = 0.04 M and [C] = 0.34 M. Which of the following is true at that moment? a. The reaction is shifting right-to-left b. The reaction is shifting left-to-right. c. The reaction is at equilibrium, so no change in concentrations is occurring. d. [B] is twice the [A]. e. No conclusion can be made without knowing ΔG o. 2. The reaction below has K c = 2.0 x 10-3 at 400 K. Calculate K p for this reaction at 400 K. N 2 (g) + 2 O 2 (g) 2 NO 2 (g) (R = L atm/mol.k). a. 6.1 x 10-5 b. 2.0 x 10-3 c. 5.0 x 10 2 d. 6.6 x 10-2 e. none of these 3. Consider the reaction CO (g) + H 2 O (g) CO 2 (g) + H 2 (g) 2.00 atm CO and 2.00 atm H 2 O were placed in a flask and allowed to reach equilibrium at a particular temperature where K p = What is p CO at equilibrium? a atm b atm c atm d atm e. Impossible to determine without the temperature. 4. The reaction below has K c = 6.5 x 10 2 at 350 K What is K c at 350 K for a. 3.1 x 10-3 b. 3.9 x 10-2 c. 2.4 x 10-6 d. 1.5 x 10-3 e. 4.2 x Consider the reaction below 2 NO (g) + 2 H 2 (g) N 2 (g) + 2 H 2 O (g) 2 N 2 (g) + 4 H 2 O (g) 4 NO (g) + 4 H 2 (g) N 2 O 4 (g) 2 NO 2 (g) At a particular moment in time, the [NO 2 ] is measured and found to be increasing. Which of the following statements must be true at that moment? a. Q c < K c b. Cannot decide without knowing the initial [N 2 O 4 ]. c. Cannot decide without knowing K c d. ΔS univ < 0 e. The left-to-right reaction is exothermic.

2 6. The reaction shown is allowed to reach equilibrium in a 2.00 L vessel at 300 K. A (g) + 2 B (g) 2 C (g) + D (g) ΔH o = kj K c = 278 at 300 K. If the temperature is now raised to 310 K, what will happen? a. The reaction will shift left-to-right, and K c will increase. b. The reaction will shift left-to-right, and K c will decrease. c. The reaction will not shift, and K c stays unchanged. d. The reaction will shift right-to-left, and K c will increase. e. The reaction will shift right-to-left, and K c will decrease. 7. Ethane (C 2 H 6 ) can be formed from the reaction of acetylene (C 2 H 2 ) with hydrogen (H 2 ). ΔH o = -311 kj for this reaction. C 2 H 2 (g) + 2 H 2 (g) C 2 H 6 (g) Which of the following conditions will push the equilibrium to the right and thus give the greatest amount of ethane at equilibrium? a. high temperature, high pressure b. low temperature, high pressure c. low temperature, low pressure d. high temperature, low pressure e. Impossible to predict. 8. What is the ph of a 0.20 M solution of Ba(OH) 2 (aq)? a b c d e. none of these 9. A solution of HCl of volume ml has a ph of 2.00 at 300 K. What is the new ph if the volume of the solution is doubled by addition of ml of pure water? a b c. none of these d e Which of the following is not a conjugate acid/base pair? a. HCN / CN - b. H 3 PO 4 / H 2 PO 4 - c. H 2 SO 4 / SO 4 2 d. NH 4 + / NH 3 e. They are all conjugate acid/base pairs. 11. A M solution of a weak acid HA has [H 3 O + ] = 3.77 x 10-4 M. What is K a for this acid? a. 3.7 x 10-5 b. 7.5 x 10-3 c. 7.0 x 10-8 d. 2.6 x e. 2.8 x What is the ph of a M solution of NR 3 H + Cl - solution? (K b for NR 3 = 5.9 x 10-7 ). a b c d e. 4.89

3 13. What is the ph of a 3.2 x 10-9 M solution of NaOH (aq)? a b c d e Farmers who raise cotton once used arsenic acid, H 3 AsO 4, as a defoliant at harvest time. Arsenic acid is a triprotic acid: K a1 = 2.5 x 10-4, K a2 = 5.6 x 10-8, and K a3 = 3.0 x What is the ph of a M solution of arsenic acid? a b c d e What is the ph of a buffer solution containing equal concentrations of HNO 2 and NaNO 2? K a for HNO 2 is 7.1 x a b c d e. Impossible to determine without the [HNO 2 ] and [NO - 2 ]. 16. At the equivalence point of a titration of 0.12 M solution of CH 3 COOH with 0.12 M NaOH, the ph of the solution will be: a. Less than 7.00 b. Greater than 7.00 c d. None of these. e. Cannot be predicted. 17. Consider the following reaction at equilibrium at 300 K: - - NO 2 + HClO 2 HNO 2 + ClO 2 What can you predict about this reaction? a. Since it is at equilibrium, K c = 1 and [HNO 2 ] = [HClO 2 ] b. The equilibrium lies to the left-hand-side (K c < 1) c. The equilibrium lies to the right-hand-side (K c > 1) d. Since it is at equilibrium, [HNO 2 ] = [HClO 2 ] e. No prediction can be made without knowing K c 18. What is the solubility of BaF 2 (s) in a 0.20 M solution of Ba(NO 3 ) 2? (K sp = 1.5 x 10-6 ). a. 1.9 x 10-3 M b. 3.8 x 10-6 M c. 8.7 x 10-3 M d. 1.4 x 10-3 M e. none of these 19. What is the K sp of the salt MX 3 (containing M 3+ and X - ions) if its molar solubility is 1.2 x 10-2 M? a. 1.9 x 10-7 b. 6.2 x 10-8 c. 4.3 x 10-6 d. 2.1 x 10-8 e. 5.6 x 10-7

4 20. Which of the following will increase the solubility of Ag 2 SO 4 in water? K sp for Ag 2 SO 4 is 1.5 x a. Lowering the ph by addition of a strong acid. b. None of these. c. Adding very soluble Na 2 SO 4 to the solution. d. Adding more Ag 2 SO 4 solid to the solution. e. Adding very soluble AgNO 3 to the solution. 21. At 350 K, the dissociation of HBrO in water has K a = 3.8 x Calculate ΔG when [H 3 O + ] = 4.0 x 10-4 M, [BrO - ] = 0.20 M and [HBrO] = 0.40 M. a. none of these b. ΔG = 32 kj c. ΔG = -81 kj d. ΔG = 81 kj e. ΔG = -32 kj HBrO (aq) + H 2 O (l) H 3 O + (aq) + BrO - (aq) 22. Calculate ΔS o for the reaction between Cu (s) and O 2 (g) to give one mole of Cu 2 O (s). S o values (J/mol.K): Cu (s) = 33.1; O 2 (g) = 205.0; Cu 2 O (s) = 93.1 a J/K b. none of these c J/K d J/K e J/K 23. Calculate ΔG o for the following reaction at 400 K, given the ΔH o f and S o values below. 3 NO (g) N 2 O (g) + NO 2 (g) ΔH o f (kj/mol) S o (J/mol.K) NO 2 (g) N 2 O (g) NO (g) a kj b kj c kj d x 10 3 kj e. None of these. 24. A particular reaction is non-spontaneous and has ΔS o rxn > 0 (positive). Which of the following statements is true? a. ΔS univ > 0 b. None of these c. ΔH o rxn > 0 d. ΔS o surr > 0 e. ΔG o < For which of the following changes is ΔS sys negative? a. Bubbles of CO 2 (g) escaping from a carbonated drink. b. Ice melting to liquid water at 0 o C. c. A liquid warming by 10 o C. d. AgCl (s) precipitating from a solution of Ag + (aq) and Cl - (aq) e. A rock rolling downhill.

5 26. The following reaction has ΔG o = 326 kj. 3 O 2 (g) 2 O 3 (g) Calculate ΔG at 309 K for the reaction when [O 2 ] = x 10-3 M and [O 3 ] = x 10-3 M. a. 286 kj b. 306 kj c. 574 kj d. 366 kj e. 346 kj 27. A reaction has ΔH = -300 kj and ΔS = -50 J/K. Which of the following statements is true? a. The reaction is non-spontaneous at low temperature, and spontaneous at high temperature. b. The reaction is spontaneous at low temperature, and non-spontaneous at high temperature. c. The reaction is spontaneous at all temperatures. d. The reaction is non-spontaneous at all temperatures. e. No conclusion can be made. 28. The reaction below has ΔG o = 0.00 kj. 2 A 3 B When some A was placed in a vessel and allowed to come to equilibrium, the [B] = 4.0 M. What is [A] at equilibrium? a. 32 M b. 8.0 M c. 16 M d. 4.0 M e. 6.0 M 29. What is the cell notation for the voltaic cell driven by the following spontaneous reaction? 2 Pb (s) + O 2 (g) + 2 H 2 O (l) 2 Pb 2+ (aq) + 4 OH - (aq) a. Pb (s) Pb 2+ (aq) O 2 (g) OH - (aq) graphite b. graphite O 2 (g) OH - (aq) Pb 2+ (aq) Pb (s) c. Pb (s) O 2 (g) Pb 2+ (aq), OH - (aq) graphite d. graphite O 2 (g) Pb 2+ (aq), OH - (aq) Pb (s) e. Pb (s) Pb 2+ (aq) OH - (aq) O 2 (g) graphite 30. Using the following half-cell potentials, determine the order of oxidizing agent strengths. Cd 2+ (aq) + 2 e - Cd (s) E o = V Cl 2 (g) + 2 e - 2 Cl - (aq) E o = 1.36 V Cu 2+ (aq) + e - Cu + (aq) E o = 0.15 V a. None of these. b. Cd 2+ (aq) > Cu 2+ (aq) > Cl 2 (g) c. Cd (s) > Cu + (aq) > Cl - (aq) d. Cl - (aq) > Cu + (aq) > Cd (s) e. Cl 2 (g) > Cu 2+ (aq) > Cd 2+ (aq) 31. What is E cell for the following voltaic cell at 298 K? Cd (s) Cd 2+ (aq, 0.45 M) Ag + (aq, 6.0 M) Ag (s) a V b V c V d V e V

6 32. What is E o cell for the voltaic cell with cell reaction 2 Al (s) + 3 Fe 2+ (aq) 2 Al 3+ (aq) + 3 Fe (s) a V b V c V d V e. None of these 33. Which of the metals, silver (Ag), copper (Cu), tin (Sn) or cadmium (Cd), could be used to spontaneously produce H 2 (g) from H + (aq) solutions? a. Cu and Ag only b. Cu, Ag and Sn c. Cd and Sn only d. Cd only e. Impossible to determine without ΔG o values 34. Which of the following statements is true about the following reaction? 2 NH 3 (aq) + 2 CrO 3 (aq) + 6 H + N 2 (g) + 2 Cr 3+ (s) + 6 H 2 O (l) a. The CrO 3 is reduced by H +, which is oxidized to H 2 O. b. The NH 3 is reduced by CrO 3, which is oxidized to Cr 3+. c. The NH 3 is oxidized by CrO 3, which is oxidized to Cr 3+. d. The CrO 3 is reduced by NH 3, which is oxidized to N 2. e. The H + is oxidized by CrO 3, which is reduced to Cr Consider the voltaic cell below. Fe (s) Fe 2+ (aq, 0.4 M) Fe 2+ (aq, 2.6 M) Fe (s) Which of the following statements is true? a. None of the statements is true. b. The [Fe 2+ ] in the anode is greater than that in the cathode. c. The [Fe 2+ ] on the left-hand side of the cell will decrease. d. Q > 1 e. Since both sides have the same half-cell reaction, no spontaneous reaction is possible and therefore E cell = 0.00 V. 36. Consider the voltaic cell below, containing equal volumes of the two solutions: Cr (s) Cr 3+ (aq, 1.0 M) Cu 2+ (aq, 1.0 M) Cu (s) After current has flowed for 20 minutes, the [Cr 3+ ] is 1.2 M. Which of the following statements is true? a. The [Cu 2+ ] after 20 minutes is 0.7 M. b. The [Cu 2+ ] after 20 minutes is 0.8 M. c. The [Cu 2+ ] after 20 minutes is 0.9 M. d. The [Cu 2+ ] after 20 minutes is 1.1 M. e. The [Cu 2+ ] after 20 minutes is 1.2 M. 37. The most covalent oxide of manganese (Mn) is: a. MnO b. Mn 2 O 7 c. MnO 2 d. Mn 2 O 3 e. MnO How many total isomers of any kind are possible for the square planar complex [PtCl 2 (NO 2 ) 2 ]? a. 3 b. 8 c. 2 d. 4 e. 6

7 39. The condensed configuration of the element zirconium (Zr) is a. [Kr] 4s 1 3d 3 b. [Kr] 3d 4 c. [Kr] 4s 2 4d 2 d. [Kr] 4d 4 e. [Kr] 4s 2 3d A metal forms an M 3+ ion with the condensed electronic configuration [Kr] 4d 6. The metal is: a. Ru b. Mo c. Rh d. Cd e. Pd 41. In the following reaction, which has K c = 3.1 x 10 4 and H o = kj, 1.0 mol of each substance is introduced into a 1.0 L vessel in the presence of a catalyst and allowed to reach equilibrium and a constant temperature. C 2 H 4 (g) + 3 O 2 (g) 2 CO 2 (g) + 2 H 2 O (l) If the volume of the vessel is then doubled, what will happen? a. the concentrations will all increase, and the reaction will then shift left-to-right. b. the concentrations will all decrease, and the reaction will then shift left-to-right. c. the concentrations will all increase, and the reaction will then shift right-to-left. d. the concentrations will all decrease, and the reaction will then shift right-to-left. e. the concentrations will all decrease, but the reaction will then not shift. 42. The compounds cis-[cr(h 2 O) 4 BrCl] + Br - and cis-[cr(h 2 O) 4 Br 2 ] + Cl - are an example of which type of isomers? a. geometric isomers b. coordination isomers c. optical isomers d. linkage isomers e. They are not isomers. 43. Which of the following is the most stable in the +7 oxidation state? a. Fe b. Tc c. Mn d. Re e. W 44. The formulas of tellurous acid and bromic acid are: a. H 2 TeO 3 and HBrO 3 b. H 3 TeO 4 and HBrO 3 c. H 3 TeO 3 and HBrO 2 d. H 2 TeO 3 and HBrO 2 e. H 2 TeO 3 and HBrO Which element has similar properties to Mg as a result of the diagonal relationship? a. Sc b. K c. Li d. B e. Ga

8 46. A metal ion in a particular oxidation state has an [Ar] 3d 5 electronic configuration. The metal ion is: a. Cr 2+ b. Mo + c. Fe 2+ d. Re 2+ e. Mn For the elements Si, Sr, Nb, and Ga, the order of the electronegativities and the metallic character are a. Si > Ga > Nb > Sr and Sr > Nb > Ga > Si b. Sr > Nb > Ga > Si and Si > Ga > Nb > Sr c. Si > Ga > Nb > Sr and Si > Ga > Nb > Sr d. Sr > Nb > Ga > Si and Sr > Nb > Ga > Si e. impossible to predict 48. Which is the most basic oxide? a. SeO 3 b. CaO c. BeO d. P 4 O 6 e. CO Which of the following is the ionic hydride? a. HCl b. B(OH) 3 c. CaH 2 d. H 2 e. CH 3 COOH 50. Hydrogen is the only element whose isotopes are given their own name and symbol. For the isotopes 1 H, 2 H and 3 H, the names and symbols are: a. protium (H), deuterium (D) and tritium (T) b. proton (H + ), hydrogen (H) and hydride (H - ) c. monodentate (H), bidentate (B) and tridentate (T) d. hydrium (H), deuterium (D) and trifillium (T) e. hydrium (H), dihydrium (D) and trihydrium (T) G = G + RT lnq pk a = -log K a G = -nfe o cell ph = -log[h + ] R = J/mol.K K = k f /k r S rxn + S surr = S univ G = -RT lnk rate = Aexp(-E a /kt) 1 ampere = 1 C/s F = 9.65 x 10 4 C/mol e - E = mc 2 E cell = Eº cell - (0.0592/n) log Q (at 25 C) ph = pk a + log ([base])/[acid]) Each student will receive a table of half-cell potentials and a Periodic Table

Bubble in A, B or C as the test form code at the top right of your answer sheet. Bubble in your Section Number also. VERSION X

CHM 2046 Practice Exam 3 Bubble in A, B or C as the test form code at the top right of your answer sheet. Bubble in your Section Number also. VERSION X 1. A reaction has ΔH = -75.0 kj and ΔS = -245 J/K.