CHM 142 Exam 4 Review
Which of the following titrations will result in a noticeably acidic solution at the equivalence point? (CH3)3N(aq) + HClO4(aq) HBr(aq) + KOH(aq) HCNO(aq) + NaOH(aq) CH3COOH(aq) + LiOH(aq) Ca(OH)2(aq) + HI(aq)
(CH3)3N(aq) + HClO4(aq)
What is the standard emf for a voltaic cell in which the following reaction occurs? 2Ag+ (aq) + Cu(s) → 2Ag(s) + Cu2+ (aq) Ag+ (aq) + e- → Ag(s) Eº = +0.80 V Cu2+ (aq) + 2e- → Cu(s)Eº = +0.34 V
+0.46 V
Kp for a reaction is equal 1.82 x 102 at 29.4 ºC. What is the value of ∆Grº (in kJ/mol) at this temperature?
-13.1
Using the standard molar entropies of O2(g) [Sº= 205.1 J/(K·mol)], NH3(g) [Sº = 192.5 J/(K·mol)], N2(g) [Sº= 191.6 J/(K·mol)], and H2O(l) [Sº= 70.0 J/(K·mol)], and the values of ∆Hfº of NH3(g) (∆Hfº= -46.1 kJ/mol) and H2O(l) (∆Hfº= -285.8 kJ/mol), calculate the value of ∆Grº for the following reaction at 25.0 ºC. 4NH3(g) + 3O2(g) → 2N2(g) + 6H2O(l)
-1356.9 kJ/mol
Estimate ∆Grº (in kJ/mol) at 745.8 K for a reaction given that at 25.00 ºC ∆Hrº=-345.3 kJ/mol and ∆Grº=-265.3 kJ/mol.
-145.43
∆Srº for a certain reaction was found to be equal to -391.1 J/(K·mol) at 25 ºC. The reaction was found to become nonspontaneous at temperatures exceeding 139.6 ºC. Given this information estimate ∆Hrº (in kJ/mol) for this reaction at 25 ºC.
-161.4
The standard emf of a cell which utilizes the reaction: Cu2+ (aq) + X(s) → X2+ (aq) + Cu(s) is 2.43 V at 25 ºC. Use this emf value as well as the following reduction potential Cu2+ (aq) + 2e- → Cu(s) Eº = +0.34 V to calculate the standard reduction potential (in V) for the following half-reaction. X2+ (aq) + 2e- → X(s)
-2.09
Calculate ∆Gº for the following reaction CH4(g) + 4Cl2(g) → CCl4(g) + 4HCl(g) given that ∆Gfº(CH4) = -50.7 kJ/mol, ∆Gfº(CCl4) = -53.6 kJ/mol, and ∆Gfº(HCl) = -95.3 kJ/mol.
-384.1 kJ/mol
Consider the two gaseous equilibria and the associated ∆Grº values 2SO3(g) → 2SO2(g) + O2(g) ∆Grº = 140.2 kJ/mol SO3(g) + NO(g) → SO2(g) + NO2(g) ∆Grº = 35.3 kJ/mol What is the value of ∆Grº for the following reaction? 2NO(g) + O2(g) → 2NO2(g)
-69.6
At 25.0 ℃, the reaction N2O4(g) -> 2NO2(g) has ΔH° = 57 kJ/mol ΔS° = 175 J/(K*mol). Calculate the ΔG° for this reaction at 100.0 °C.
-8 kJ/mol
Given that ΔGf°[H2O(l)] = -237.12 kJ/mol and ΔGf°[HCl(g)] = -95.30 kJ/mol find ΔG° for the following reaction at 25°C. 4HCl(g) + O2(g) -> 2Cl2(g) + 2H2O(l)
-93.06 kJ
In which of the following aqueous solutions would you expect AgBr to have the lowest solubility? 0.030 M KBr pure water 0.010 M MgBr2 0.020 M FeBr3 0.020 M AgNO3
0.020 M FeBr3
Find the value of the equilibrium constant, Kp, for the following reaction N2O(g) + NO2(g) → 3NO(g) at 900 K given the following data: N2O(g): ∆Gfº=149.2 kJ/mol; NO2(g): ∆Gfº=89.4 kJ/mol; NO(g): ∆Gfº=79.0 kJ/mol.
1.21
Find the molar solubility (in mM) of salt of the A3B2 type given the solubility product constant: Ksp = 4.74 x 10-13.
1.34
At 25 ºC, the solubility product constant (Ksp) for silver arsenate, Ag3AsO4, is 1.03 x 10-22. What is the molar solubility of Ag3AsO4?
1.4 x 10-6 M
Nitrosyl chloride (NOCl) decomposes at elevated temperature according to the following equation. 2NOCl(g) → 2NO(g) + Cl2(g) Given that ΔH° = 81.2 kJ/mol and ΔS° = 128 J/(K*mol), calculate the value of Kp for this reaction at 227°C.
1.6 * 10-2
Nitrosyl chloride (NOCl) decomposes at elevated temperatures according to the equation. 2NOCl(g) → 2NO(g) + Cl2(g) Use the following information to calculate the value of Kp for this reaction at 227.0 ºC. ∆Hrº = 81.2 kJ/mol, ∆Srº = 128. J/K·mol
1.6 x 10-2
What is the molar solubility of Ag2SO3 in water? For Ag2SO3, Ksp = 1.5x10-14.
1.6 x 10^-5 mol/L
What is the sum of the smallest possible integer coefficients when the skeletal redox reaction below is correctly balanced? H2O2(aq) + Cl2O7(aq) → ClO2-(aq) + O2(g) (basic solution) [Note that H2O(l) and OH-(aq) may have to be added where necessary to balance the equation and should be included when you calculate the sum.]
18
Find the pKsp for a salt of the AB3 type given that its molar solubility is 7.71 µM.
19.02
The concentration of PO43- ions in a saturated solution of cadmium phosphate, Cd3(PO4)2, was found to be 2.4 x 10-7 M. What is the Ksp for Cd3(PO4)2?
2.7 x 10-33
What is the molar solubility of PbBr2 in a 0.15 M solution of KBr? Ksp(PbBr2) = 6.6 x 10-6.
2.9 x 10-4 M
What is the sum of the smallest possible integer stoichiometric coefficients when the skeletal redox reaction below is correctly balanced? MnO4-(aq) + SO32-(aq) → Mn2+(aq) + SO42-(aq) (acidic solution)
23
∆Hrº for a certain reaction was found to be equal to 74.2 kJ/mol at 298 K. The reaction was found to be spontaneous under standard conditions at temperatures exceeding 36.7 ºC. Given this information estimate ∆Srº for this reaction.
239 J/(K·mol)
Use the following data 3N2H4(g) → 4NH3(g) + N2(g) ∆Srº = 240.6 J/(K·mol) Sº(N2(g))=216.9 J/(K· mol) Sº(NH3(g))=227.8 J/(K· mol) obtained at 700.0 K to find Sº of N2H4(g).
295.9 J/(K·mol)
Identify the reaction for which ΔS is negative. 2NO2(g) -> 2NO(g) + O2(g) 2NH3(g) -> N2(g) + 3H2(g) 2Na(s) + Cl2(g) -> 2NaCl(s) C(s) + H2O(g) -> CO(g) + H2(g) C6H6(s) -> C6H6(l)
2Na(s) + Cl2(g) -> 2NaCl(s)
Calculate the concentration of fluoride ions in a saturated solution of chromium fluoride (CrF3). Ksp(CrF3) = 6.6 x 10-11
3.9 x 10-3 M
The standard molar entropies [in J/(K·mol)] of N2, F2 and NF3 at 500 K are 206.74, 219.74 and 292.18, respectively. What is ∆Sº (in J/K) for the decomposition of 0.271 mol of NF3? The reaction to consider is 2NF3(g) → N2(g) + 3F2(g).
38.2
Find the concentration of CrO4 ions needed to begin precipitation of Ag2CrO4 from a solution that contains 4.82x10-3 M Ag+. Ksp (Ag2CrO4) = 1.12x10-12
4.8x10-8 M
Find ∆S (in J/K) for a reversible isothermal expansion of 0.618 mol of an ideal gas when it expands from 2.69 L to 7.03 L at 39.7 ºC.
4.94
How many electrons are transferred in the following redox reaction when it is balanced with the smallest possible integer coefficients? ClO3-(aq) + NO(g) → Cl-(aq) + NO2-(aq) (basic solution) [Note that H2O(l) and OH-(aq) may have to be added where necessary to balance the equation.]
6
How many electrons are transferred in the following redox reaction when it is balanced with the smallest possible integer coefficients? Cr2O72-(aq) + Cl-(aq) → Cr3+(aq) + ClO3-(aq) (acidic solution) [Note that H2O(l) and H+(aq) may have to be added where necessary to balance the equation and should be included when you calculate the sum.]
6
Consider a 2.5 x 10-2 M aqueous solution of Pb(NO3)2. What is the minimal concentration of I- ions required to begin the precipitation of PbI2? Ksp(PbI2) = 9.8 x 10-9.
6.3 x 10-4 M
What is the molar solubility of PbI2 in a 0.125 M solution of KI? Ksp(PbI2) = 9.8 x 10-9.
6.3 x 10-7 M
Calculate the molar solubility of AgCl (Ksp = 1.8 x 10-10) in a 0.0250 M solution of NaCl
7.2 x 10^-9 M
N2 has a normal boiling point of -195.80℃ and the molar enthalpy of vaporization ΔH°vap = 5.586 kJ/mol. Calculate the molar entropy of vaporization (ΔS°vap).
72.22 J/(K*mol)
Find the molar entropy of vaporization (in J/(K·mol)) for a certain substance given that to vaporize 0.228 mol of that substance at -43.4 ºC ∆H = 3.94 kJ.
75.2
Consider a 8.40 x 10-3 M aqueous solution of La(NO3)3. What is the minimal concentration of IO3- ions required to begin the precipitation of La(IO3)3? For La(IO3)3, Ksp =7.50 x 10-12.
9.64 x 10-4 M
For the reaction, N2(g) + 3H2(g) → 2NH3(g) ∆Hrº = -92.38 kJ/mol and ∆Srº = -198.3 J/(K·mol) at 298 K. Calculate ∆Grº (in kJ/mol) for this reaction at 516.1 K.
9.96
Which of the following is the correct expression for the solubility product of Cd3(PO4)2? A) Ksp = [Cd2+]3[PO43-]2 B) Ksp = [Cd]3[PO4]2 C) Ksp = [Cd2+][PO43-] D) Ksp = [3Cd2+]3[2PO43-]2 E) Ksp = [Cd2+]3[PO43-]2/[Cd3(PO4)2]
A) Ksp = [Cd2+]3[PO43-]2
Given the overall chemical reaction that takes place in a voltaic cell choose the half-reaction that occurs at the anode. Sn4+(aq) + 2Ag(s) + 2Br-(s) → Sn2+(aq) + 2AgBr(s)
Ag(s) + Br-(s) → AgBr(s) + e-
Use the standard reduction potentials for several half-reactions given below to choose the strongest oxidizing agent among those shown. Ag+ (aq) + e- → Ag(s) Eº = +0.80 V Cu2+ (aq) + 2e- → Cu(s) Eº = +0.34 V Ni2+ (aq) + 2e- → Ni(s) Eº = -0.25 V Zn2+ (aq) + 2e- → Zn(s) Eº = -0.77 V Al3+ (aq) + 3e- → Al(s) Eº = -1.66 V
Ag+(aq)
Which of the following salts will not be significantly more soluble in acidic solution than in pure water? AgBr BaCO3 PbF2 ZnS Ba3(PO4)2
AgBr
Which of the following salts will not be significantly more soluble in acidic solution than in pure water? AgBr CuCO3 MgF2 Ag2SO3 Li3PO4
AgBr
Which of the following statements is true for a voltaic cell? Anions migrate to the anode and electrons flow from the anode to the cathode Cations migrate to the cathode and electrons flow from the cathode to the anode Anions migrate to the anode and electrons flow from the cathode to the anode Cations migrate to the anode and electrons flow from the anode to the cathode Cations migrate to the anode and electrons flow from the cathode to the anode
Anions migrate to the anode and electrons flow from the anode to the cathode
For which of the following reactions is ∆Grº negative at low temperatures, but can become positive at higher temperatures under standard conditions? A) 2NOCl(g) → 2NO(g) + Cl2(g)∆Hrº = 77.1 kJ/mol B) 2NO(g) + O2(g) → 2NO2(g)∆Hrº = -114 kJ/mol C) 2NO2Cl(g) → 2NO2(g) + Cl2(g)∆Hrº = -42 kJ/mol D) 2NH3(g) → N2(g) + 3H2(g) ∆Hrº = 92.6 kJ/mol E) NO2(g) + N2O(g) → 3NO(g)∆Hrº = 156 kJ/mol
B
Identify the oxidizing and reducing agents in the following unbalanced equation. Cr2O72-(aq) + S2O32-(aq) → Cr3+(aq) + S4O62-(aq) Oxidizing Agent Reducing Agent ACr2O72-S4O62- BCr2O72-S2O32- CS4O62-Cr3+ DS2O32-Cr2O72- ECr2O72-Cr3+
B
For which of the following reactions is ∆Sº negative? 2NO2(g) → 2NO(g) + O2(g) CH3OH(l) → CH3OH(g) 2H2O2(l) → 2H2O(l) + O2(g) Br2(l) + H2(g) → 2HBr(g) Ba2+(aq) + SO42-(aq) → BaSO4(s)
Ba2+(aq) + SO42-(aq) → BaSO4(s)
For which of the following elements is ∆Gfº not Iequal to 0.0 kJ/mol at 298 K and 1 bar? H2(g) F2(g) Cl2(g) N2(g) Br2(g)
Br2(g)
For which of the following reactions is K > 1 at all temperatures? A) 2NOCl(g) → 2NO(g) + Cl2(g)∆Hrº = 77 kJ/mol B) 2NO(g) + O2(g) → 2NO2(g)∆Hrº = -114 kJ/mol C) 2NO2(g) → N2(g) + 2O2(g)∆Hrº = -66 kJ/mol D) 2NH3(g) → N2(g) + 3H2(g) ∆Hrº = 93 kJ/mol E) NO2(g) + N2O(g) → 3NO(g)∆Hrº = 156 kJ/mol
C
Which of the following hydrocarbons has the smallest standard molar entropy (S) at 25oC? C2H2(g) C6H6(g) C4H10(g) C3H8(g) C2H6(g)
C2H2(g)
Which of the following species has the highest standard molar entropy (Sº) at 25 ºC? CaCl2(s) C4H10(g) C2H5OH(l) N2O(g) CH3OH(g)
C4H10(g)
Which of the following titrations will result in a noticeably basic solution at the equivalence point? KOH(aq) + HI(aq) HCl(aq) + NaOH(aq) CH3COOH(aq) + NaOH(aq) NH3(aq) + HClO4(aq) NaHCO3(aq) + HCl(aq)
CH3COOH(aq) + NaOH(aq)
Which of the following salts will have greater solubility in acidic solution than pure water? BiI3 PbCl2 CaF2 Hg2Br2 KClO4
CaF2
The overall reaction for the discharge of a voltaic cell is Pb(s) + Cu2+(aq) → Pb2+(aq) + Cu(s) . Which one of the following statements is true? The anode is made of copper and its mass decreases during the operation of the cell. The cathode is made of lead and its mass increases during the operation of the cell. Copper electrode is positive in this voltaic cell. The electrons flow from copper to lead. Copper is a stronger reducing agent than lead.
Copper electrode is positive in this voltaic cell.
Ammonium nitrate (NH4NO3) dissolves spontaneously and endothermically in water. What are the signs of ∆Srº, ∆Hrº and ∆Grº for this process? ∆Srº∆Hrº∆Grº A--+ B+-- C-+- D+++ E++-
E
For which of the following reactions is ∆Sº positive? CO2(g) → CO2(s) O2(g) + 2SO2(g) → 2SO3(g) CaO(s) + SO2(g) → CaSO3(s) H2O(s) → H2O(l) Ag+(aq) + Cl-(aq)→ AgCl(s)
H2O(s) → H2O(l)
Which of the following statements about voltaic cells is not always true? In an operating voltaic cell electrons flow from the anode towards the cathode. In an operating voltaic cell anions migrate towards the anode. In an operating voltaic cell the reduction half-reaction occurs at the cathode. In an operating voltaic cell the mass of an anode decreases. In an operating voltaic cell cations migrate towards the cathode.
In an operating voltaic cell the mass of an anode decreases.
ΔG° for which reaction is equal to the standard molar Gibbs energy of formation (ΔG°f) of KClO4(s)?
K(s) + ½ Cl2(g) + 2O2(g) -> KClO4(s)
The expression for the solubility-product constant for zirconium fluoride, ZrF4, is
Ksp = [Zr4+] [F-]4
∆Grº for which of the following reactions is equal to ∆Gfº of lithium bromate? Li(s) + ¹⁄₂Br2(g) + ³⁄₂O2(g) → LiBrO3(s) Li(s) + ¹⁄₂Br2(l) + ³⁄₂O2(g) → LiBrO3(s) Li(g) + ¹⁄₂Br2(l) + ³⁄₂O2(g) → LiBrO3(s) Li(s) + ¹⁄₂Br2(s) + ³⁄₂O2(g) → LiBrO3(s) Li(g) + ¹⁄₂Br2(g) + ³⁄₂O2(g) → LiBrO3(s)
Li(s) + ¹⁄₂Br2(l) + ³⁄₂O2(g) → LiBrO3(s)
Will a precipitate of Ba(IO3)2 form when 50.0 mL of 4.2 x 10-3 M Ba(NO3)2 solution is added to 50.0 mL of 2.2 x 10-3 M NaIO3? For Ba(IO3)2, Ksp = 4.0 x 10-9.
No, Qsp < Ksp
Consider a solution in which concentrations of Ca2+, Sr2+ and Ba2+ ions are all 1.00 x 10-4 M. If enough solid Na2SO4 is added to this solution so that the concentration of SO42- ions is 1.0 x 10-3 M which sulfates(s) will precipitate? The solubility product constants are: CaSO4: Ksp = 4.9 x 10-5 SrSO4: Ksp = 3.4 x 10-7 BaSO4: Ksp = 1.1 x 10-10
Only BaSO4 will precipitate.
For the reaction 2NO(g) + O2(g) → 2NO2(g) ∆Hrº = -114 kJ/mol and ∆Srº = -146 J/(K·mol) at 25 ºC. Which of the following statements is true? Reaction is spontaneous at temperatures lower than 781 K. Reaction is spontaneous at all temperatures. Reaction is nonspontaneous at all temperatures. Reaction is spontaneous at temperatures higher than 781 K. Reaction is nonspontaneous at temperatures lower than 781 K.
Reaction is spontaneous at temperatures lower than 781 K.
Which of the following species is reduced in the following redox reaction? Zn(s) + SO42-(aq) + 4H+(aq) → Zn2+(aq) + SO2(g) + 2H2O(l)
SO42-(aq)
At 25 °C, ΔH° = 85 kJ/mol for the following reaction. N2F4(g) -> 2NF2(g) This reaction is
Spontaneous only at high temperatures
To a solution in which concentrations of Ba2+, Cd2+, and Mg2+ were all equal to 0.010 M, solid NaF was added to make the concentration of NaF equal to 2.5 x 10-3 M. Given the Ksp's of the three fluorides: BaF2: Ksp = 1.84 x 10-7 CdF2: Ksp = 6.44 x 10-3 MgF2: Ksp = 5.16 x 10-11 predict the composition of the precipitate that will form.
The precipitate will contain only MgF2.
In which solutions the molar solubility of NiCO3 will be greater than in pure water? A: 0.010 M Ni(NO3)2 B: 0.010 M NH3 C: 0.010 M HCl D: 0.010 M Na2CO3
only B and C
For which of the three phase transitions: deposition, fusion and sublimation is ∆S negative?
only deposition
What should be the approximate value of pKa of an indicator that can be used to titrate a solution of a weak acid with a solution of a strong base? pKa = 4 pKa = 5 pKa = 13 pKa = 9 pKa = 7
pKa = 9
Which of the following indicators is suitable for the titration of 0.10 M CH3COOH (Ka = 1.8 x 10-5) with 0.15 M NaOH? methyl orange (Ka = 2.0 x 10-4) phenolphthalein (Ka = 4.0 x 10-10) bromocresol green (Ka = 2.0 x 10-5) bromothymol blue (Ka = 1.0 x 10-7) methyl red (Ka = 7.9 x 10-6)
phenolphthalein (Ka = 4.0 x 10-10)
Arrange the following reactions according to increasing ∆Sº. 1: 2C(s) + O2(g) → 2CO(g) 2: H2O(g) → H2O(l) 3: 2NaHCO3(s) → Na2CO3(s) + H2O(g) + CO2(g)
∆Sº(2) < ∆Sº(1) < ∆Sº(3)
Arrange the following reactions according to increasing ∆Sº. 1: 2NH3(g) → N2(g) + 3H2(g) 2: N2O4(g) → 2NO2(g) 3: 2NO(g) + O2(g) → 2NO2(g)
∆Sº(3) < ∆Sº(2) < ∆Sº(1)
