CHM 1143 Third Hour Exam Spring 2003 Each question is worth 10 points. You get six free misses. Write the letter of your choice to the right of the answer choices. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) A chemical system is at equilibrium A) when the concentration of reactants and products are equal. B) when all of the reactants have been used up. C) when the rate of the forward reaction becomes zero. D) when the rates of the forward reaction and the reverse reaction are both zero. E) when the rates of the forward reaction and the reverse reaction are equal. 2) The value of Kc is changed when A) the concentration of reactants are changed. B) the volume of the system is changed. C) the pressure of the system is changed. D) the temperature of the system is changed. E) a catalyst is added. 3) For the following reaction, define each of the species as acid, base, conjugate acid, and conjugate base. H2SO4 + H2O H3O+ + HSO4 - A) Base + Acid π> Conjugate Base + Conjugate Acid B) Base + Acid π> Conjugate Acid + Conjugate Base C) Acid + Base π> Conjugate Base + Conjugate Acid D) Acid + Base π> Conjugate Acid + Conjugate Base E) These aren't acids and bases. 4) Which is the strongest base? A) F- B) Cl- C) Br- D) I- E) None of these are bases. 5) The ph of acid rain may be as low as 2.80. What is the H3O+ in such acidic rain? A) 1.6 B) 9.7 10-2 C) 6.3 10-12 D) 1.6 10-3 E) 630 6) What is the [OH-] in an aqueous solution of orange juice with [H3O+] = 3.4 10-4 M? A) 1.00 10-14 B) 10.53 C) 3.47 D) 3.4 10-4 E) 2.9 10-11 7) Calculate the ph of a 0.0015 M HCl solution. A) 2.82 B) 1.5 C) 11.17 D) 3.84 E) 1.5 10-3
8) Calculate the poh of a 3.5 10-2 M NaOH solution. A) 11.46 B) 12.54 C) 2.46 D) 1.46 E) 0.46 9) Determine the ph of 0.35 M HOCl. The Ka of HOCl is 2.9 x 10-8. A) 4.00 B) 7.53 C) 8.00 D) 1.00 10-4 E) 3.12 10) What molarity of propanoic acid, C3H6O2, is required to produce an aqueous solution with ph = 2.40? (Ka = 1.3 10-5) A) 2.4 B) 1.2 C) 3.3 10-3 D) 0.83 E) 306 11) Consider 0.10 M solutions of the following substances. Which would have the lowest ph? A) NaCl B) NH4NO3 C) Na2CO3 D) KCN E) NH4F 12) Given the following Ka values, HC2H3O2 1.8 10-5 HClO3 5.0 102 HCN 6.2 10-10 HF 6.6 10-4 HOCl 2.9 10-8 which of the following is the weakest base? A) C2H3O2 - B) CN- C) OCl- D) ClO3 - E) F- 13) Calculate the ph after 10.0 ml of 0.40 M NaOH is added to 20.0 ml of 0.50 M HCl. A) 0.30 B) 0.70 C) 13.30 D) 13.70 E) 7.00 14) The ph of a solution formed by mixing 20.0 ml of 0.250 M formic acid, HCOOH, and 8.0 ml of 0.400 M NaOH is 3.99. Determine the Ka for formic acid. A) 1.8 10-4 B) 1.0 10-4 C) 1.2 10-5 D) 1.6 10-4 E) 1.8 10-5
15) Examine the titration curve shown above. Which of the following titrations could it represent? A) HCl by NaOH B) HCl by NH3 C) H2SO4 by NaOH D) Ca(OH)2 by HCl E) NH3 by HCl 16) Examine the titration curve shown above. What is the ph at the equivalence point? A) 1 B) 3 C) 7 D) 10 E) 12 17) Examine the titration curve shown above. The volume of titrant required to reach the end point of the titration is approximately A) 20 ml. B) 40 ml. C) 60 ml. D) 80 ml. E) 90 ml. 18) What must be the concentration of CH3COO- ion in 0.40 M CH3COOH to produce a buffer solution with ph = 4.80? (Ka CH3COOH = 1.8 10-5) A) 1.6 10-5 B) 0.46 C) 2.7 10-3 D) 4.74 E) 0.40 19) Calculate the molar solubility of PbI 2. (Ksp = 7.1 x 10-9) A) 1.9 x 10-3 B) 1.5 x 10-3 C) 8.4 x 10-5 D) 4.8 x 10-3 E) 1.2 x 10-3 20) What is the molar solubility of PbI2 in a solution that contains 0.30 M KI? (Ksp = 7.9 x 10-9) A) 2.6 x 10-8 B) 1.3 x 10-8 C) 8.8 x 10-8 D) 2.4 x 10-9 E) 7.9 x 10-7 21) What [CrO4 2- ] must be present in 0.0025 M AgNO3 (aq) to just cause Ag2CrO4 (s) to precipitate? (Ksp = 2.4 x 10-12) A) 1.5 x 10-13 B) 1.8 x 10-9 C) 3.8 x 10-7 D) 0.0050 E) 9.6 x 10-10
22) The following reaction is spontaneous at room temperature. CH4 (g) + 2 O2 (g) CO2 (g) + 2 H2O (l) The reverse reaction A) is spontaneous. B) is not spontaneous. C) is exothermic. D) has a larger equilibrium constant, Kp. E) is faster than the forward reaction. 23) The ultimate criterion for spontaneity of a process is A) the change in internal energy of the process. B) the change in enthalpy. C) the change in entropy. D) the change in free energy for the process. E) the change in numbers of moles of gaseous species. 24) For a certain reaction, the enthalpy change is -148.5 kj, the entropy change is 256 J/K, and the free energy change is -250.1 kj. At what temperature is the reaction occurring, in ec? A) 85 B) 102 C) 124 D) 158 E) 210 25) The following reaction is exothermic: CO2 (g) + 2 H2 (g) CH3OH (l). The reaction is A) spontaneous at all temperatures. B) non-spontaneous at all temperatures. C) spontaneous at low temperatures. D) spontaneous at high temperatures. 26) Calculate DGe, in kj, for the following reaction at 25eC if the value of Keq is 6.1 x 10-58. 3 O2 (g) 2 O3 (g) A) -27.4 B) 326 C) 27.4 D) 3.22 E) -326
Answer Key Testname: CHM 1143 EXAM3 SP03.TST MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) E 2) D 3) D 4) A 5) D 6) E 7) A 8) D 9) A 10) B 11) B 12) D 13) B 14) A 15) D 16) C 17) B 18) B 19) E 20) C 21) C 22) B 23) D 24) C 25) C 26) B