Study guide III chapter 18-19 Chem 162 with answers PDF

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Study guide III, Chemistry 162 Useful equations and constants: ΔG = ΔH – T∙ΔS, ΔG = ΔG° + RTlnQ, R = 8.314 J/K• mol, F = 96 485.3365 s•A/mol, E°cell = (0.059V/n) log K, E = E° - (0.0592/n) log Q, ΔG° = -RTlnK, ΔG = -nFE°cell 2+ 1.) Fe ( s )| Fe ( a q )| | Pb2+( a q )| Pb ( s ), Wr i t et h eHa l f Re a c t i on sa n dOv e r a l lRe a c t i o n 2+ 2+ t o t : Pb ( a q)+Fe ( s )® Fe ( a q)+Pb ( s ) E° =+0 . 3 2V o x i da t i o nha l f c e l lo nl e f t ,r e d uc t i o nhal f c e l lo nt her i g ht 2 + o x : Fe ( s )® Fe ( a q)+2e − E° =+0 . 45V 2+ r e d : Pb ( a q)+2e −® Pb( s ) E° =−0 . 1 3

2.) Consider a reaction that has a positive ΔH and a positive ΔS. Which of the following statements is TRUE? Thus ΔG needs to be negative, so the higher the temperature the more negative ΔG becomes. ΔG = ΔH – TΔS A) This reaction will be spontaneous only at high temperatures. B) This reaction will be spontaneous at all temperatures. C) This reaction will be nonspontaneous at all temperatures. D) It is not possible to determine without more information. 3.) Place the following in order of decreasing standard molar entropy. (N2O3, NO2, NO) A) N2O3 > NO2 > NO more atoms means more states, more variable motion, etc = more entropy B) N2O3 > NO > NO2 C) N2O3 > NO2 > N2O3 D) NO > NO2 > N2O3 4.) What element is undergoing reduction in the following redox reaction? MnO4⁻(aq) + H2C2O4(aq) → Mn2+(aq) + CO2(g) A) C B) O C) Mn D) H Mn was reduced thus is the oxidizing agent Mn7+ → Mn2+ 5.) Calculate the ΔG°rxn using the following information. 4 HNO3(g) + 5 N2H4(l) → 7 N2(g) + 12 H2O(l) ΔG°rxn = ? ΔG°f (kJ/mol) -73.5 149.3 0.0 -237.1 3 A) -3.298 x 10 kJ ΔG = ΔGfinal – ΔGinitial = [7(0) + 12(-237.1)] – [4(-73.5) + 5(149.3)] = -3.297.7 B) -312.9 kJ C) +2.845 x 103 kJ D) +110.7 kJ 6.) Wh a ti st h eo x i d a t i o ns t a t eo fs ul f u ri nSO4-2?+6 , o xy g e ni s2 , t he r ea r e4o x y g e nsg i v i ng8a ndt he o v e r a l lc ha r g ei s2 , t huss ul f ur so xi da t i o ni s+6

2

7.) What element is being oxidized in the following redox reaction? Cr(OH)4⁻(aq) + ClO⁻(aq) → CrO42-(aq) + Cl⁻(aq) A) Cr Usually metals get oxidized, Cr+3 to Cr+6 B) O C) H D) Cl 8.) Balance the following redox reaction if it occurs in acidic solution. What are the coefficients in front of H⁺ and Fe3+ in the balanced reaction? Fe2+(aq) + MnO4⁻(aq) → Fe3+(aq) + Mn2+(aq) A) H⁺ = 2, Fe3+ = 3 B) H⁺ = 8, Fe3+ = 5 C) H⁺ = 3, Fe3+ = 2 D) H⁺ = 5, Fe3+ = 1 9.) Identify the location of reduction in an electrochemical cell. A) the anode B) the cathode C) the electrode

D) the salt bridge

10.) I nt hef o l l o wi n gr e a c t i o n,Zn ( s )+F2( g )→ Zn F2( s ) a )Zni so x i d i z e d, Fi sr e duc e d, Zni st her e duc i nga g e nt , F2i st heo x i d i z i nga g e nt b )Fi so xi d i z e d, Zni sr e d u c e d, F2i st h er e du c i n ga g e n t ,Zni st h eo xi d i z i n ga g e nt c )n e i t h e ri sb e i n go x i d i z e do rr e d u c e d 11.) Define a salt bridge. A) A pathway, composed of salt water, that ions pass through. B) A pathway in which no ions flow. C) A pathway between the cathode and anode in which ions are reduced. D) A pathway by which counterions can flow between the half-cells without the solutions in the half-cell totally mixing. 12.) Use the standard half-cell potentials listed below to calculate the standard cell potential for the following reaction occurring in an electrochemical cell at 25°C. (The equation is balanced.) 3 Cl2(g) + 2 Fe(s) → 6 Cl⁻(aq) + 2 Fe3+(aq) Cl2(g) + 2 e⁻ → 2 Cl⁻(aq) E° = +1.36 V Fe3+(aq) + 3 e⁻ → Fe(s) E° = -0.04 V A) +6.16 V

B) -1.40 V

C) -1.32 V

D) +1.40 V

E) none

13.) Identify the characteristics of a spontaneous reaction. A) ΔG° < 0 B) ΔE°cell > 0 C) K > 1 D) all of the above E) none of the above 14.) Calculate the cell potential for the following reaction that takes place in an electrochemical cell at 25°C.

3 Cu(s) ∣ Cu2+(aq, 0.0032 M) ∣∣ Cu2+(aq, 4.48 M) ∣ Cu(s) A) 0.00 V B) +0.093 V C) +0.34 V D) +0.186 V E) +0.052 V E = E° - (0.0592/n ) log Q E = 0 - (0.0592/2) log (0.0032 / 4.48 M) = 0 – (-0.09321) = +0.093 V 15.) What is the reaction at the anode in a breathalyzer? A) Ethanol (ethyl alcohol) is oxidized to acetic acid. B) Acetic acid is reduced to ethanol. C) Oxygen is reduced. D) Hydrogen is oxidized. 16.) Describe the reactions during the electrolysis of water. 2 H2O  2 H2 + O2 A) Oxygen is reduced and hydrogen is oxidized. B) Oxygen and hydrogen are both oxidized. C) Oxygen and hydrogen are both reduced. D) Oxygen is oxidized and hydrogen is reduced. 17.) Balance the following redox reaction if it occurs in basic solution. What are the coefficients in front of Cr and Cl2 in the balanced reaction? Cr(s) + Cl2(g) → Cr3+(aq) + Cl-(aq) A) Cr = 2, Cl2 = 3 B) Cr = 2, Cl2 = 6 C) Cr = 1, Cl2 = 1 D) Cr = 2, Cl2 = 1 E) none of these 18.) What is the reducing agent in the redox reaction represented by the following cell notation? Zn(s) ∣ Zn2+(aq) ∣∣ Ag+(aq) ∣ Ag(s) A) Pt B) Zn2+(aq) C) Ag+(aq) D) Ag(s) E) Zn(s) 19.) What is true if ln K is negative? A) ΔGorxn is positive and the reaction is spontaneous in the forward direction. B) ΔGorxn is negative and the reaction is spontaneous in the forward direction. C) ΔGorxn is negative and the reaction is spontaneous in the reverse direction. D) ΔGorxn is positive and the reaction is spontaneous in the reverse direction. ΔG ° = -RTlnK, if lnK is negative then ΔG ° is positive, thus nonspontaneous (or spontaneous in reverse direction) 20.) Which of the following reactions will have the largest equilibrium constant (K) at 298 K? A) CaCO3(s) → CaO(s) + CO2(g) ΔG° =+131.1 kJ B) 2 Hg(g) + O2(g) → 2 HgO(s) ΔG° = -180.8 kJ Δ G = -nFE° cell C) 3 O2(g) → 2 O3(g) ΔG° = +326 kJ D) Fe2O3(s) + 3 CO(g) → 2 Fe(s) + 3 CO2(g) ΔG° = -28.0 kJ

4 Ch 17 question/worksheets 1.) When titrating a strong monoprotic acid and KOH at 25°C, the (Draw the titration curve) A) pH will be less than 7 at the equivalence point. B) pH will be greater than 7 at the equivalence point. C) titration will require more moles of base than acid to reach the equivalence point. D) pH will be equal to 7 at the equivalence point. E) titration will require more moles of acid than base to reach the equivalence point.

2.) Determine the molar solubility of MgCO3 in pure water. Ksp (MgCO3) = 6.82 × 10-6. D) 2.61 × 10-3 M A) 6.82 × 10-6 M B) 3.41 × 10-6 M C) 4.65 × 10-3 M MgCO3  Mg2+ + CO32I C +x +x E x x x = 2.61 × 10-3 M Ksp = x2  6.82x10-6 3.) Give the equation for a supersaturated solution in comparing Q with Ksp. A) Q > Ksp B) Q < Ksp C) Q = Ksp D) Q ≠ Ksp E) none...