HCCS Dept Final CHEM 1412 Fall Houston Community College System. General Chemistry II CHEM 1412

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1 Houston Community College System General Chemistry II CHEM 1412 Departmental Final Exam Fall 2012

2 CHEM 1412 Final Exam Part I: Multiple Choice (35 questions, 2 pts each) Select the BEST answer and mark it clearly on your Scantron. 1. Which of the following compounds should be soluble in CCl 4? A) NaCl B) H 2 O C) NaOH D) C 8 H 18 E) None of these 2. What is the molality of a solution that is 3.68 % by mass calcium chloride. A) m B) m C) m D) m E) m 3. What is the osmotic pressure of a solution that contains 13.7 g of propyl alcohol (C 3 H 7 OH) dissolved in enough water to make 500. ml of solution at 27 C? A) atm B) atm C) atm D) atm E) 11.2 atm 4. What is the boiling point of a solution of 12.0 g of urea (CH 4 N 2 O) in g of water? (K b (H 2 O) = 0.52 C/m) A) 99.4 C B) C C) C D) C E) C 5. Chlorine dioxide reacts in basic water to form chlorite and chlorate according to the following chemical equation: 2ClO 2 (aq) + 2OH (aq) ClO 2 (aq) + ClO 3 (aq) + H 2 O(l) Under a certain set of conditions, the initial rate of disappearance of chlorine dioxide was determined to be 2.30 x 10 1 M/s. What is the initial rate of appearance of chlorite ion, (ClO 2 ), under those same conditions? A) 5.75 x 10 2 M/s D) 4.60 x 10 1 M/s B) 1.15 x 10 1 M/s E) 9.20 x 10 1 M/s C) 2.30 x 10 1 M/s 6. Appropriate units for a second-order rate constant are A) M/s B) 1/M s C) 1/s D) 1/M 2 s 7. The first-order decomposition, A products, has a rate constant of s 1. Starting with [A] o = M, how much time is required for [A] t = M? A) 6.86 s B) 2.98 s C) 34 s D) 1.50 s E) 4.62 s

3 8. The graphs below all refer to the same reaction. What is the order of this reaction? A) zero order B) first order C) second order D) unable to predict 9. A reaction with an equilibrium constant K c = 1.5 x would consist of which of the following at equilibrium: A) approximately equal reactants and products B) some reactants and products with reactants slightly favored C) some reactants and products with products slightly favored D) essentially all reactants E) essentially all products 10. K p for the reaction 4CuO(s) 2Cu 2 O(s) + O 2 (g) is 0.49 at 1024 C. Calculate K c at this Temperature A) 5.8 x 10 3 B) 41 C) 52 D) 4.6 x 10 3 E) Which is the correct equilibrium constant expression for the following reaction? Fe 2 O 3 (s) + 3H 2 (g) 2Fe (s) + 3H 2 O (g) A) K c = [Fe 2 O 3 ] [H 2 ] 3 / [Fe] 2 [H 2 O] 3 D) K c = [Fe] 2 [H 2 O] 3 / [Fe 2 O 3 ] [H 2 ] 3 B) K c = [H 2 ] / [H 2 O] E) K c = [Fe] [H 2 O] / [Fe 2 O 3 ] [H 2 ] C) K c = [H 2 O] 3 / [H 2 ] According to Le Chatelier s Principal, the addition of more H 2 gas to the reaction below would shift the equilibrium in which direction? N 2 (g) + 3H 2 (g) 2NH 3 (g) A) right, to generate products C) left, to generate reactants B) left, to generate products D) right, to generate reactants 13. What is the concentration of OH in a 2.5 x10 3 M HCl solution? A) 0 B) 4 x M C) 2.5 x M D) 5.0 M E) 1.0 x10 3 M 14. The ph of a M Ca(OH) 2 solution is A) 2.70 C) 11.3 B) 3.0 D) 11

4 15. What is the ph of a 0.10 M NH 3 solution (K b = 1.8 x10 5 )? A) 2.87 C) 5.74 B) D) A poh value of 2 will be indicative of a solution A) very acidic B) very basic C) neutral D) slightly acidic E) slightly basic 17. Which solution will have the lowest ph? A) 0.10 M HCN D) 0.10 M H 2 CO 3 B) 0.10 M HNO 3 E) 0.10 M NaOH C) 0.10 M NaCl 18. What is the ph of a M solution of HCN (K a = 4.9 x )? A) 1.64 B) C) 3.05 D) 5.47 E) Which one of the following combinations cannot function as a buffer solution? A) HCN and KCN D) HF and NaF B) NH 3 and (NH 4 ) 2 SO 4 E) HNO 2 and NaNO 2 C) HNO 3 and NaNO For which type of titration will the ph be basic at the equivalence point? A) Strong acid vs. strong base. D) All of the above. B) Strong acid vs. weak base. E) None of the above. C) Weak acid vs. strong base. 21. The solubility of lead(ii) iodide is g/100 ml at 20ºC. What is the solubility product for lead(ii) iodide (molar mass PbI 2 = g/mol)? A) B) C) D) E) The molar solubility of magnesium carbonate is mol/l. What is K sp for this compound? A) B) C) D) E) Which of the following processes would be accompanied by an increase in entropy? A) evaporation D) sublimation B) H 2 O(l) H 2 O(s) E) A & D C) Recrystallization of sugar from water

5 24.Which of the following equations is used to calculate the standard entropy change of a reaction? A) m(s reactants)- m(s products) D) (S products)- (S reactants) B) m(s products)- m(s reactants) C) (S reactants)- (S products) 25. Calculate the Gibbs free energy (ΔG ) of a reaction at 25 C when ΔH = 250 kj/mol and ΔS = 2.1 J/Kmol. A) kj D) kj B) kj C) kj 26. Beta particles are identical to A) protons. D) helium nuclei. B) helium atoms. E) electrons. C) hydrogen atoms. 27. When atoms of aluminum-27 are bombarded with alpha particles, a neutron and an element are produced. The particular isotope formed is 4 27 He Al 1 0 n + A) Si B) Si C) S D) P E) P 28. If a certain radioisotope has a decay constant of 1.2 x 10 3 days 1, what is the half-life of this isotope? A) days B) 578 days C) 112 days D) 173 days 29. Polonium-208 is an alpha emitter with a half-life of 2.90 years. How many milligrams of polonium from an original sample of 2.00 mg will remain after 8.00 years? A) mg B) mg C) mg D) 6.77 mg E) 1.90 mg 30. Alkanes have the general formula A) C n H 2n 4 B) C n H 2n 2 C) C n H 2n D) C n H 2n+2 E) C n H 2n+4

6 31. Which option represents 1-butene? A) CH 3 CH 2 CH 2 CH 3 D) CH 2 =CHCH 2 CH 2 CH 3 B) CH CCH 2 CH 3 E) CH 3 CH=CHCH 3 C) CH 2 =CHCH 2 CH The correct structure for 2,3,3-trimethylpentane is A) C) B) 33. Which one of these structures represents an ester functional group? D) 34.Calculate E cell for a silver-aluminum cell in which the cell reaction is Al(s) + 3Ag + (aq) Al 3+ (aq) + 3Ag(s) Ag + (aq) + e Ag (s) E cell = 0.80 V Al 3+ (aq) + 3e Al (s) E cell = 1.66 A) 2.46 V B) 0.86 V C) 0.86 V D) 2.46 V E) none of these 35. Consider the following standard reduction potentials in acid solution: Cr e Cr Co e Co MnO 4 + 8H + + 5e Mn H 2 O E = 0.74 V E = 0.28 V E = V The strongest oxidizing agent listed above is A) Cr 3+. B) Cr. C) Mn 2+. D) Co 2+. E) MnO 4.

7 Short Answer (5 pts each): Answer each question completely in the space provided. Please box your final answer(s). Partial credit will be given. 1. What is the ph of a buffer solution containing 0.20M HF/0.40M NaF? What would be the resulting ph if 20 ml of 0.5 NaOH were added to 75mL of the buffer solution? The pka value for hydrofluoric acid is Balance the following redox reaction in an ACIDIC medium: Cr 2 O 7 2 (aq) + HNO 2 (aq) Cr 3+ (aq) + NO 3 (aq) 3. What is the cell potential of a cell made of Zn/Zn 2+ and Cu/Cu 2+ at 25 C if [Zn 2+ ] = 0.50M and [Cu 2+ ]= 0.10M?

8 4. Ethylene glycol (C 2 H 6 O 2, FW=62 g/mol), a liquid coolant, is added to a car radiator to help prevent overheating. How many ml of the solute (density= 1.11 g/ml) should be added to 500 ml of water to allow a maximum freezing point of 108 C? The K b of water is 0.52 C/m and normal boiling point is 100 C. 5. Using the data below for reaction A + B > C, write a) the rate law for the reaction and b) calculate the value of the rate constant, k. Trial [A] [B] Rate # x 10 4 # x 10 4 # x At equilibrium, there are 4 mols of N 2, 12 mols H 2, and 8 mols of NH 3 gas contained in a 2 L vessel. What is the value of the equilibrium rate constant for the reaction. Reference the equation below: N 2 (g) + 3H 2 (g) 2NH 3 (g)

9 KEY MC: VA KEY SA: 1. D 2. C 3. E 4. C 5. B 6. C 7. A 8. A 9. D 10. D 11. C 12. A 13. B 14. C 15. B 16. B 17. B 18. D 19. C 20. C 21. A 22. D 23. E 24. B 25. B 26. E 27. D 28. B 29. B 30. D 31. C 32. A 33. E 34. D 35. E ml 2. Rate = k [A] [B] 0 ; k= 4.0 x 10 4

10 3. k= or 3.7 x ph= 4.45; ph= equivalence point 5. 5H + (aq) + Cr 2 O 7 2 (aq) + 3HNO 2 (aq) 2Cr 3+ (aq) + 4H 2 O (l) + 3NO 3 (aq) 6. E cell = 1.1V; E= 1.08V n= 2 7.

Houston Community College System General Chemistry 1412 Departmental Final Exam

Houston Community College System General Chemistry 1412 Departmental Final Exam Aspirin, C 9 H 8 O 4 - Acetylsalicylic Acid was originally derived from Salicin the active ingredient in Willow bark. drug