Practice Exam 3 (1).pdf

Equations and Constants Sheet Constant R = 8.3145 𝐽/(𝐾 ⋅ 𝑚𝑜𝑙) R = 0.08206 𝐿 ⋅ 𝑎𝑡𝑚/(𝐾 ⋅ 𝑚𝑜𝑙) Equations ΔSsurr = –ΔH/T ΔG = ΔH - TΔS ΔG° = -RT lnK ΔG° = ΔH° - TΔS°...

Equations and Constants Sheet Constant R = 8.3145 𝐽/(𝐾 ⋅ 𝑚𝑜𝑙) R = 0.08206 𝐿 ⋅ 𝑎𝑡𝑚/(𝐾 ⋅ 𝑚𝑜𝑙) Equations ΔSsurr = –ΔH/T ΔG = ΔH - TΔS ΔG° = -RT lnK ΔG° = ΔH° - TΔS° ΔG = ΔG° + RT lnQ Chem 101B Practice Test Chapter 15 – Solution Equilibria Multiple Choice (total 10 pts) 1. Predict whether adding potassium nitrate impacts the solubility of ammonium nitrate. NH4NO3(s) ⇌ NH4+ (aq) + NO3-(aq) A) solubility decreases B) solubility increases C) solubility does not change 2. The correct mathematical expression for finding the molar solubility (S) of Sn(OH)2 is: A) 2S2 = Ksp B) 2S3 = Ksp C) 108S5 = Ksp D) 4S3 = Ksp E) 8S3 = Ksp –10 3. The molar solubility of AgCl (Ksp = 1.6 × 10 ) in 0.0034 M sodium chloride at 25°C is: A) 0.0034 B) 4.7 × 10–8 –10 C) 1.6 × 10 –13 D) 5.4 × 10 E) none of these Free Response (total 18 points) a. (4 pts). Write the ionic equation for dissolution and the solubility product constant expression, Ksp, for cerium iodate, Ce(IO3)3. - -3 b. (6 pts). The [IO3 ] in a saturated solution of Ce(IO3)3 is 5.91 × 10 M. Calculate the Ksp for Ce(IO3)3. (10 pts). Which of the following compounds precipitates from a solution that has the concentrations indicated? a. CaCO3: [Ca2+] = 0.003 M, [CO32-] = 0.003 M; Ksp of CaCO3= 8.7 x 10-9 b. Co(OH)2: [Co2+] = 0.01 M, [OH–] = 1 × 10-7M ; Ksp of Co(OH)2= 2.5 x 10-16 Chapter 17 – Thermochemistry Multiple Choice (Total 12 pts) 4. Which of the following processes is spontaneous under the specified conditions? A) H2O(l) → H2O(s) at 25°C B) CO2(s) → CO2(g) at 0°C C) 2H2O(g) → 2H2(g) + O2(g) at all temperatures D) C(graphite) → C(diamond) at 25°C and 1 atm pressure E) 3O2(g) → 2O3(g) at all temperatures 5. A certain process has ΔSuniv > 0 at 25°C. What does one know about the process? A) It is exothermic. B) It is endothermic. C) It is spontaneous at 25°C. D) It will move rapidly toward equilibrium. E) None of the above 6. Which of the following is always true for an exothermic process? A) q sys > 0, ΔSsurr < 0 B) q sys < 0, ΔSsurr > 0 C) q sys < 0, ΔSsurr < 0 D) q sys > 0, ΔSsurr > 0 E) w < 0  7. For a reaction in a voltaic cell both ΔH° and ΔS° are positive. Which of the following statements is true? A) E°cell will increase with an increase in temperature. B) E°cell will decrease with an increase in temperature. C) E°cell will not change when the temperature increases. D) ΔG° > 0 for all temperatures. E) None of the above statements is true. 8. The heat of vaporization for 1.0 mole of water at 100.°C and 1.0 atm is 40.56 kJ/mol. Calculate DS for the process H2O(l) ® H2O(g) at 100.°C. A) 109 J/K mol B) –109 J/K mol C) 406 J/K mol D) –406 J/K mol E) None of these 9. The standard free energy of formation of AgI(s) is –66.2 kJ/mol. What is ΔG° for the reaction 2AgI(s) ® 2Ag(s) + I2(s) is: A) 66.2 kJ B) –66.2 kJ C) 132.4 kJ D) –132.4 kJ E) None of these Multiple Choice (Total 6 pts) 10. Given: CH3COOH(aq) H+(aq) + CH3COO–(aq) Ka = 1.75 ´ 10–5 at 25°C and with initial concentrations of: [CH3COOH]0 = 0.10 M [H+]0 = 4.8 ´ 10–8 M [CH3COO–]0 = 0.010 M What is DG at 25°C for the solution? A) 19.7 kJ B) –19.7 kJ C) 27.1 kJ D) 74.0 kJ E) –74.0 kJ Free Response (total 29 points) (6 pts). Select all that apply. Place a check in the space to the left for all processes that involve an increase in the entropy of the system. [__] condensation of a gas [__] mixing 5 mL ethanol with 25 mL water [__] grinding large crystals of KCl 1into a powder [__] heating 1.0 mol of an ideal gas at constant volume [__] compressing 1 mol Ne at constant temperature from 1.5 L to 0.5 L [__] (8 pts). For each pair, which species has the higher entropy? Write it in the space provided, followed by explain why it is higher. a. Mg(NO₃)₂(s), Mg(NO₃)₂(aq) _______________ ____________________________ b. Al(s), Ag(s) _______________ ____________________________ c. Ar(g), Hg(l) _______________ ____________________________ d. O2(g), O3(g) _______________ ____________________________ (5 pts). Describe the thermodynamic parameters for the following process as either: + (positive sign) , - (negative sign) or 0 (zero) When a stable diatomic molecule spontaneously forms from its atoms. ΔSsystem _____ ΔHsystem _____ ΔSsurrounding _____ ΔG ______ ΔSuniverse ______ 1 (10 pts). Consider the reaction at 25 °C: 2SO2(g) + O2(g) -> 2SO3(g) ΔH°f (kJ∙mol-1) S°f (J∙K-1∙mol-1) and use the following thermodynamic data: SO2(g) -297 248 SO3(g) -396 257 O2(g) 0 205 What is the standard free-energy change, ΔG°, for the reaction where all gases are at 1.00 atm pressure? Electrochemistry Multiple Choice (total 8 pts) 11. In the reaction 2Ca(s) + O2(g) → 2CaO(s), which species is oxidized? A) O2 B) O2– C) Ca D) Ca2+ E) none of these 12. In the reaction 2Cs(s) + Cl2(g) → 2CsCl(s), Cl2 is: A) the reducing agent. B) the oxidizing agent. C) oxidized. D) the electron donor. E) two of these. 13. In the reaction N2(g) + 3H2(g) → 2NH3(g), N2 is: A) oxidized. B) reduced. C) the electron donor. D) the reducing agent. E) two of these. 14. Given the reaction: 2MnO4– + 5H2O2 + 6H+ → 2Mn2+ + 8H2O + 5O2 Determine the number of electrons involved in this reaction. A) 10 B) 8 C) 6 D) 4 E) 2 15. Which of the following are oxidation-reduction reactions? I. PCl3 + Cl2 → PCl5 II. Cu + 2AgNO3 → Cu(NO3)2 + 2Ag III. CO2 + 2LiOH → Li2CO3 + H2O IV. FeCl2 + 2NaOH → Fe(OH)2 + 2NaCl A) III B) IV C) I and II D) I, II, and III E) I, II. III, and IV Free Response (total 20 points) (5 pt) Write the oxidation state for the nitrogen atom in each ion or molecules HNO3 ____ NO2_____ N2O _____ NH4Cl _____ NaNO2 ___ (7 pts). Balance the reaction in acidic solution:: Zn + As2O3 → AsH3 + Zn2+ (acid)  - 2+ 2. (8 pts). Balance the reaction in basic solution: MnO4 (aq) + HCOOH(aq) → Mn (aq) + CO2(g)