4. [7 points] Which of the following reagents would decrease the solubility of AgCl(s)? NaOH HCl NH 3 NaCN

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1 1. [7 points] It takes g of silver iodate, AgIO 3, to make 1.00-L of a saturated solution saturated at 25 C. What is the value of the solubility product, K sp? a b c d e [7 points] The K sp for PbCl 2 is Determine the molar solubility of PbCl 2? a M b M c M d M e M 3. [7 points] What is the molar solubility of PbI 2 (K sp = ) in a M NaI solution? a M b M c M d M e. None of the above 4. [7 points] Which of the following reagents would decrease the solubility of AgCl(s)? NaOH HCl NH 3 NaCN a. NH 3 b. NH 3 & NaCN c. NaOH & NH 3 d. HCl e. None of these reagents will decrease the solubility of AgCl(s)

2 5. [7 points] Given the fact that K sp = for Cr(OH) 3, and that the formation constant for the complex ion, Cr(OH) 4, is K f = What is the concentration of the complex ion Cr(OH) 4 in a solution that is buffered at ph = 11 and is in equilibrium with solid Cr(OH) 3? a b c d e [7 points] What is the concentration of free Ni 2+, if 1.83 g of Ni(NO 3 ) 2 is dissolved in 1.00 L of 3.0 M NH 3 solution? [The formation constant for the formation of the complex ion Ni(NH 3 ) 6 2+ is ] a b c d e [7 points] An amphoteric oxide (i.e. ZnO) is an oxide that. a. Dissolves in strongly acidic solution, but not strongly basic solution b. Dissolves in strongly basic solution, but not strongly acidic solution c. Dissolves in both strongly acidic and strongly basic solutions d. Only dissolves when the ph is nearly neutral e. Sleeps with both metals and nonmetals 8. [7 points] In the laboratory you add 0.25 g of Ca(OH) 2 to 500 ml of H 2 O and stir the solution. After 2 minutes the solid has completely dissolved. The solution is then divided into three beakers. To each of these beakers you add 100 ml of the following solutions: Beaker 1: 100 ml of 6 M HCl solution Beaker 2: 100 ml of 6 M NaCl solution Beaker 3: 100 ml of 6 M CaCl 2 solution This leads to the formation of a white precipitate in which of the beakers? a. Beaker 1 b. Beaker 2 c. Beaker 3 d. Beakers 1 & 2 e. Beakers 1, 2 & 3

3 9. [7 points] A solution contains three cations with the following concentrations, 0.10 M Cr 3+, 1.50 M Cu 2+ and 2.00 M Cd 2+. If a dilute NaOH solution is slowly added to the solution what is the first precipitate to form: Cr(OH) 3 (K sp = ), Cu(OH) 2 (K sp = ), or Cd(OH) 2 (K sp = )? a. Cr(OH) 3 b. Cu(OH) 2 c. Cd(OH) 2 d. All three precipitates will begin to form when the first drop of NaOH is added 10. [7 points] The K sp for AgIO 3 is When 50 ml of M AgNO 3 solution is mixed with 10 ml of M NaIO 3 solution will a precipitate form? a. No, because Q = and since it is larger than K sp no precipitate will form b. Yes, because Q = and since it is larger than K sp a precipitate will form c. No, because Q = and since it is larger than K sp no precipitate will form d. Yes, because Q = and since it is larger than K sp a precipitate will form e. Not enough information is given to answer this question 11. [7 points] A solution that contains one or more of the following ions Ag +, Sn 4+, Ni 2+, Fe 3+, Cu 2+ is subjected to the following steps: Step Action Result 1 Add NaCl solution A white precipitate forms (ppt A), which is separated from a green decantate (soln 1) 2 Add HCl and H 2 S to soln 1 A yellow precipitate forms (ppt B), which is separated from a green decantate (soln 2) 3 Add 3 M NaOH solution to ppt B 4 The ph of soln 2 is made basic by adding 3 M NH 3 solution and buffering with NH 4 Cl The precipitate dissolves to form a colorless solution The color of the solution changes from green to blue, no precipitate forms Which cations are present in the solution? a. Sn 4+, Cu 2+ and Ni 2+ b. Sn 4+ and Ni 2+ c. Ag +, Sn 4+ and Ni 2+ d. Ag +, Sn 4+, Cu 2+ and Ni 2+ e. Ag +, Sn 4+ and Cu 2+

4 12. [7 points] You are given a solution and told that it contains two cations. To test for the identity of the cations you add 15 M NH 3 and 3 M NH 4 Cl. This causes the solution to turn pink and leads to the formation of a white gelatinous precipitate. From the choices below which two cations are most likely to be present in the solution? a. Fe 3+ and Co 2+ b. Zn 2+ and Ni 2+ c. Al 3+ and Co 2+ d. Al 3+ and Cr 3+ e. Zn 2+ and Co [7 points] What of the following sulfides is white? a. CoS b. ZnS c. NiS d. PbS e. SnS [7 points] What reagent(s) could be used to separate Sb 2 S 5 from CuS? a. HCl (aq) b. H 2 SO 4 (aq) c. K 2 Cr 2 O 7 (aq) d. NaOH (aq) e. CH 3 CSNH 2 (aq) + heat 15. [7 points] How could you separate PbCl 2 from AgCl? a. Add the solids to water and heat b. Add the solids to a concentrated NH 3 solution c. Add the solids to a concentrated HCl solution d. Add the solids to a K 2 Cr 2 O 7 solution e. Either (a) or (b) could be used to separate the two

5 16. [7 points] A solution that contains one or more of the following ions Cu 2+, Fe 3+, Pb 2+, Al 3+ and Sb 5+ is subjected to the following steps: Step Action Result 1 The acidity of the solution was adjusted to a ph = 0.4 with HNO 3, thioacetamide (CH 3 CSNH 2 ) was added and the solution was heated A dark precipitate forms (ppt A), which is separated from a colorless decantate (soln 1) 2 Add 3 M NaOH solution to ppt A 3 Add 6 M HNO 3 solution to ppt B There is no apparent change in the precipitate (ppt B), which is separated from a colorless decantate (soln 2) The precipitate dissolves to form a colorless solution (soln 3) 4 Add 9 M H 2 SO 4 to soln 3 A white precipitate forms (ppt C) and the solution remains colorless 5 3 M HCl is added to soln 2 to make the solution slightly acidic 6 NH 3 and NH 4 Cl are added to the solution from step 5 until it becomes basic Nothing happens, A white precipitate forms. The solution remains colorless Which cations are present in the solution? a. Pb 2+, Sb 5+ and Al 3+ b. Cu 2+ and Fe 3+ c. Pb 2+ and Cu 2+ d. Pb 2+ and Al 3+ e. It s not possible to definitely identify the cations present from these observations 17. [7 points] Which of the following hydroxides is not amphoteric? a. Fe(OH) 3 b. Cr(OH) 3 c. Al(OH) 3 d. None of these hydroxides is amphoteric e. All of these hydroxides are amphoteric

6 18. [7 points] Which of the following statements is false? a. Spontaneous processes are always irreversible b. ΔG is always negative for a spontaneous process c. ΔS system is always positive for a spontaneous process d. A spontaneous process may be exothermic or endothermic 19. [7 points] For which of the following reactions would you expect ΔS rxn to be positive? a. 2SO 2 (g) + O 2 (g) 2SO 3 (g) b. C 2 H 5 OH(l) + 3O 2 (g) 2CO 2 (g) + 3H 2 O(g) c. Hg(l) Hg(s) d. CaO(s) + CO 2 (g) CaCO 3 (s) e. None of the above reactions will have a positive ΔS For problems 20 and 21 consider the reaction depicted below (all molecules shown are in the gas phase): Reactants Products 20. [7 points] Predict the sign of ΔH rxn and ΔS rxn for the reaction shown above. a. ΔS rxn is positive, ΔH rxn is positive b. ΔS rxn is negative, ΔH rxn is positive c. ΔS rxn is positive, ΔH rxn is negative d. ΔS rxn is negative, ΔH rxn is negative 21. [7 points] What general statement can you make about the relationship between spontaneity and temperature for the reaction shown above. a. The reaction is spontaneous at all temperatures b. The reaction is not spontaneous at any temperature c. The reaction becomes more spontaneous as the temperature decreases d. The reaction becomes more spontaneous as the temperature increases e. There is not enough information given to answer this question

7 Use the following standard thermodynamic quantities as appropriate to answer problems Compound ΔH f º (kj/mol) ΔG f º (kj/mol) Sº (J/mol- K) MgCl 2 (s) H 2 O (g) MgO (s) HCl (g) Br 2 (l) Br 2 (g) [7 points] The hydrolysis of magnesium chloride occurs through the following reaction: MgCl 2 (s) + H 2 O(g) MgO(s) + 2 HCl(g) What is the value of ΔG 0 for this reaction under standard conditions (pressure = 1 atm, T = 298 K)? a. 61 kj b. +61 kj c kj d kj e kj 23. [7 points] What is the value of ΔG 0 for the hydrolysis of magnesium chloride at 450 K (assume entropy and enthalpy do not change as a function of temperature)? a. 174 kj b. +79 kj c. -54,800 kj d kj e. +43 kj 24. [7 points] What value would you estimate for the boiling point of Br 2 (where the liquid and vapor are in equilibrium) if we assume entropy and enthalpy do not change as a function of temperature? a. 57 C b. 272 C c. 125 C d. 305 C e. None of the above

8 25. [7 points] Consider the reaction: NH 3 (g) + HCl (g) NH 4 Cl (s) Given the following table of thermodynamic data at 298 K: Compound ΔH f º (kj/mol) Sº (J/mol- K) NH 3 (g) HCl (g) NH 4 Cl (s) The value of the equilibrium constant K eq for the reaction at 25 C is. a. K eq = 150 b. K eq = c. K eq = d. K eq = e. K eq = Useful Equations ΔG = ΔH - TΔS ΔGº rxn = ΣnΔG º f(products) - ΣmΔG º f(reactants) ΔG = ΔGº + RT ln(q) K eq = exp[-δgº/rt]

9 Physical Constants h = J-s c = m/s R = J/K-mol 1 Å = 10 pm = m 1 ev = J 1 F = 96,500 C/mol = 96,500 J/V-mol 1 A = 1 C/s 1 ev = J Formation Constants for Some Metal Complex Ions in Water at 25 C