Exam 3 Flashcards
The phase diagram for xenon has a solid-liquid curve with a positive slope. Which of the following is true?
Solid xenon has a higher density than liquid xenon.
Pentane, C5H12, boils at 35°C. Which of the following is true about kinetic energy, Ek, and potential energy, Ep, when liquid pentane at 35°C is compared with pentane vapor at 35°C?
Ep(g) > Ep(l); Ek(g) ≈ Ek(l)
Examine the phase diagram for the substance Bogusium (Bo) and select the correct statement.
Point B represents the critical temperature and pressure for Bo.
Positive slope = Bo (s) has a higher density than Bo (l)
Neon atoms are attracted to each other by
London dispersion forces.
Which of the following atoms should have the greatest polarizability?
A)F
B)Br
C)Po
D)Pb
E) He
D) Pb
Polarizability increases down a group but decreases across a period as increasing Zeff makes atoms smaller and it more difficult to remove electrons
Cations are less polarizable
Anions are more polarizable
Which one of the following substances will have hydrogen bonds between molecules?
A)(CH3)3N
B)CH3–O–CH3
C)CH3CH2–OH
D)CH3CH2–F
E)HI
C) CH3CH2–OH
Hydrogen bonding is the ability of a O, N, F bonded with a hydrogen to form bonds with hydrogens on adjacent molecules
Intermolecular forces increase _________ (up/down) group which follows a similar trend as boiling point increases _________ (up/down) a group.
IMF increases down group with increasing molar mass and more electrons.
Boiling point increases with increasing molecular force as the molecules are held more tightly and less are in the
Which of the following pairs is arranged with the particle of higher polarizability listed first?
A)Se2−, S2−
B)I, I−
C)Mg2+, Mg
D)Br, I
E)None of these choices are correct.
A)Se2−, S2−
Polarizability increases down a group
Anion is more polarizable than cation
Which of the following should have the highest boiling point?
A)CF4
B)CCl4
C)CBr4
D)CI4
D)CI4
Boiling point increases with IMF which increases with molar mass
When the electron cloud of a molecule is easily distorted, the molecule has a high:
polarizability
Which of the following atoms should have the smallest polarizability?
A)Si
B)S
C)Te
D)Bi
E)Br
B) S
Which of the following pairs is arranged with the particle of higher polarizability listed first?
A)CCl4, CI4
B)H2O, H2Se
C)C6H14, C4H10
D)NH3, NF3
E)None of these choices are correct.
C)C6H14, C4H10
Which of the following should have the lowest boiling point?
A)C5H12
B)C6H14
C)C8H18
D)C10H22
E)C12H26
IMF increases with molar mass. Lowest molar mass = lowest boiling point for like compounds
Which of the following results in a decrease in the entropy of the system?
A)O2(g), 300 K → O2(g), 400 K
B)H2O(s), 0°C → H2O(l), 0°C
C)N2(g), 25°C → N2(aq), 25°C
D)NH3(l), −34.5°C → NH3(g), −34.5°C
E)2H2O2(g) → 2H2O(g) + O2(g)
C)N2(g), 25°C → N2(aq), 25°C
Entropy decreases from gas to liquid to solid
Gas to liquid to solid is exothermic
solid to liquid to gas is endothermic
Which of the following should have the greatest molar entropy at 298 K?
A)CH4(g)
B)H2O(l)
C)NaCl(s)
D)N2O4(g)
E)H2(g)
D)N2O4(g)
Gasses will have the highest entropies
Larger molecules in the same group will have more energy levels in a condensed level thereby increasing the entropy.
Entropy increases with number of atoms in the compound.
For allotropes, entropy is higher in the form which:
Allows for greater freedom of motion
Which of the following is true for a system at equilibrium?
A)ΔS°sys = ΔS°surr
B)ΔS°sys = −ΔS°surr
C)ΔS°sys = ΔS°surr = 0
D)ΔS°univ > 0
E) None of these choices are correct.
B)ΔS°sys = −ΔS°surr
Which of the following is always true for an exothermic process?
A)qsys > 0, ΔSsurr < 0
B)qsys < 0, ΔSsurr > 0
C)qsys < 0, ΔSsurr < 0
D)qsys > 0, ΔSsurr > 0
E)w < 0
B)qsys < 0, ΔSsurr > 0
Which relationship or statement best describes ΔS° for the following reaction?
HgS(s) + O2(g) → Hg(l) + SO2(g)
A)ΔS° ≈ 0
B)ΔS° < 0
C)ΔS° > 0
D)ΔS° = ΔH°/T
E)More information is needed to make a reasonable prediction.
C)ΔS° > 0
Which of the following pairs has the member with the greater molar entropy listed first? All systems are at 25°C.
A)CO(g), CO2(g)
B)NaCl(s), NaCl(aq)
C)H2S(g), H2S(aq)
D)Li(s), Pb(s)
E)H2(g), H2O(g)
C)H2S(g), H2S(aq)
Entropy of gas > entropy solution
Which one of the following phase changes decreases the entropy of the system?
A)Melting
B)Heating a gas
C)Vaporization
D)Condensation
E)Sublimation
Correct answer D)Condensation (gas->liquid)
Melting (solid to liquid) increases entropy
Heating a gas causes molecules to have more kinetic energy increasing number of microstates
Vaporization (liquid to gas) increases entropy
Sublimation (solid to gas) increases entropy
For a chemical reaction to be spontaneous only at low temperatures, which of the following conditions must be met?
A)ΔS° > 0, ΔH° > 0
B)ΔS° > 0, ΔH° < 0
C)ΔS° < 0, ΔH° < 0
D)ΔS° < 0, ΔH° > 0
E)ΔG° > 0
C)ΔS° < 0, ΔH° < 0
ΔG°=ΔH°-ΔS°T
For a chemical reaction to be non-spontaneous at any temperature, which of the following conditions must be met?
A)ΔS° > 0, ΔH° > 0
B)ΔS° > 0, ΔH° < 0
C)ΔS° < 0, ΔH° < 0
D)ΔS° < 0, ΔH° > 0
E)All reactions are spontaneous at some temperature.
D)ΔS° < 0, ΔH° > 0
Consider the following balanced redox reaction:
Mn2+(aq) + S2O82−(aq) + 2H2O(l) → MnO2(s) + 4H(aq) + 2SO42−(aq)
Which of the following statements is true?
A)Mn2+(aq) is the oxidizing agent and is reduced.
B)Mn2+(aq) is the oxidizing agent and is oxidized.
C)Mn2+(aq) is the reducing agent and is oxidized.
D)Mn2+(aq) is the reducing agent and is reduced.
E)Manganese does not change its oxidation number in this reaction.
C)Mn2+(aq) is the reducing agent and is oxidized.
When the following redox equation is balanced with smallest whole number coefficients, the coefficient for the hydrogen sulfate ion will be
Al(s) + HSO4(aq) + OH−(aq) → Al2O3(s) + S2−(aq) + H2O(l)
1.
3.
4.
8.
None of these choices are correct.
3
A voltaic cell is prepared using copper and silver. Its cell notation is shown below.
Cu(s) | Cu2+(aq) || Ag+(aq) | Ag(s)
Which of the following processes occurs at the cathode?
A) Cu(s) → Cu2+(aq) + 2e−
B) Cu2+(aq) + 2e− → Cu(s)
C) Ag(s) → Ag+(aq) + e−
D) Ag+(aq) + e− → Ag(s)Correct
E) Cu(s) + 2Ag+(aq) → Cu2+(aq) + 2Ag(s)
D) Ag+(aq) + e− → Ag(s)
An OXidation
Rededuction CAT
Consider the nonaqueous cell reaction
2Na(l) + FeCl2(s) ⇄ 2NaCl(s) + Fe(s)
for which E°cell = 2.35 V at 200°C. Calculate ΔG° at this temperature:
ΔG°=(-n)(F)(E°cell)
-453 kJ
The value of the equilibrium constant for the reaction of nickel(II) ions with cadmium metal is 1.17 × 105. Calculate ΔG° for the reaction at 25°C.
ΔG°=-RT ln K
-29 kJ
A concentration cell consists of two Zn/Zn2+ electrodes. The electrolyte in compartment A is 0.10 M Zn(NO3)2 and in compartment B is 0.60 M Zn(NO3)2. What is the voltage of the cell at 25°C?
E°cell= -(0.05916/n) * log [Dil]/[Conc]
