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Chemistry
Q:
The standard molar entropy for Br2(g) is 245.46 J/(mol K) at 25C. Given that ΔS = 104.58 J/K for the dissociation of one mole of Br2(g) into Br(g) at 25C, find the standard molar entropy for Br(g) at 25C.
A) 70.44 J/(mol K)
B) 140.08 J/(mol K)
C) 175.02 J/(mol K)
D) 350.04 J/(mol K)
Q:
Calculate ΔS for the formation of one mole of solid sodium bromide from the elements at 25C. A) -116.7 J/K
B) -81.2 J/K
C) -40.5 J/K
D) 86.8 J/K
Q:
ΔS = " 198.7 J/K for the reaction shown below. Calculate S for NH3(g).
N2(g) + 3 H2(g) → 2 NH3(g) A) 61.7 J/Kmol
B) 123.4 J/Kmol
C) 192.3 J/Kmol
D) 384.6 J/Kmol
Q:
Calculate ΔS for the following reaction.
N2(g) + 2 O2(g) → 2 NO2(g) A) -156.5 J/K
B) -121.5 J/K
C) 15.5 J/K
D) 636.5 J/K
Q:
Which one of the following has the lowest standard molar entropy, S, at 25C?
A) C8H18(s)
B) C8H18(l)
C) C12H26(s)
D) C12H26(l)
Q:
Which substance has the highest standard molar entropy at 25C ?
A) C(graphite)
B) C2H4(g)
C) CH3OH(l)
D) MgCO3(s)
Q:
Which of the following gas molecules has the greatest standard molar entropy at 25C?
A) C2H2
B) CH2CH2
C) CH3CH3
D) All have the same entropy.
Q:
Which has the highest standard molar entropy at 25C?
A) F2(g)
B) Cl2(g)
C) Br2(g)
D) I2(g)
Q:
Which has the highest standard molar entropy at 25C?
A) Al(s)
B) Al(l)
C) Al(g)
D) All three should have a standard molar entropy of zero.
Q:
Under which of the following conditions would one mole of Ne have the highest entropy, S?
A) 27C and 25 L
B) 137C and 25 L
C) 27C and 35 L
D) 137C and 35 L
Q:
Which of the following statements must be true for the entropy of a pure solid to be zero?
I. The temperature must be 0 K.
II. The solid must be crystalline, not amorphous.
III. The solid must be perfectly ordered.
IV. The solid must be an element.
A) I
B) I and II
C) I, II, and III
D) I, II, III, and IV
Q:
According to the third law of thermodynamics,
A) energy is conserved in any transformation of matter.
B) the entropy increases for any spontaneous process.
C) the entropy of a perfectly ordered, crystalline substance is zero at 0 Kelvin.
D) the entropy of the universe increases for any spontaneous process.
Q:
Which provides the greatest increase in entropy?
A) H2O (s, 0C) → H2O (l, 0C)
B) H2O (l, 0C) → H2O (l, 25C)
C) H2O (g, 0.1C) → H2O (s, 0.1C)
D) H2O (l, 100C) → H2O (g, 100C)
Q:
Which has the highest entropy in each set?
I. H2O(s), H2O(l), H2O(g) at 0.1C, 4.58 atm
II. H2O(l) at 0C, H2O(l) at 25C, H2O(l) at 100C (all at 1.0 atm pressure)
A) H2O(l) in set I and H2O(l) at 0C in set II
B) H2O(s) in set I and H2O(l) at 100C in set II
C) H2O(g) in set I and H2O(l) at 0C in set II
D) H2O(g) in set I and H2O(l) at 100C in set II
Q:
Which has the lowest entropy?
A) CH3OH(s, "25C)
B) CH3OH(s, "15C)
C) CH3OH(l, 15C)
D) CH3OH(l, 25C)
Q:
What is the sign of â–³S for each of the following processes?
I. The separation of gaseous molecules of UF6, into 238UF6 and 235UF6 at constant temperature and pressure.
II. The dissolving of I2(s) in CCl4(l).
A) ΔS is negative for I and negative for II.
B) ΔS is negative for I and positive for II.
C) ΔS is positive for I and negative for II.
D) ΔS is positive for I and positive for II.
Q:
The Boltzmann formula is S = k ln W. A perfect crystal has a molar entropy of 0 at absolute zero because
A) W = 0.
B) W = 1.
C) W = NA.
D) k = 1.
Q:
Assume a heteronuclear diatomic molecule, AB, forms a one-dimensional crystal by lining up along the x-axis. Also assume that each molecule can only have one of six possible orientations, corresponding to atom A facing in either the positive or negative direction along the x-, y-, or z-axis. If the molecules are arranged randomly in the six directions, the molar entropy at absolute zero should be
A) R ln 6.
B) R ln 66.
C) R ln 6!
D) 0.
Q:
Predict the sign of S for each of the following processes, which occur at constant temperature.I. The volume of 2.0 moles of O2(g) increases from 44 L to 52 L.II. The pressure of 2.0 moles of O2(g) increases from 1.0 atm to 1.2 atm.A) I: S= negative; II: S= negativeB) I: S= negative; II: S= positiveC) I: S= positive; II: S= negativeD) I: S= positive; II: S= positive
Q:
What is the entropy change associated with the expansion of one mole of an ideal gas from an initial volume of V to a final volume of V of 2.50V at constant temperature?A) S = 2.50 R ln (Vf/Vi)B) S = -2.50 R ln (Vf/Vi)C) S = R ln 2.50D) S = -R ln 2.50
Q:
The entropy change associated with the expansion of one mole of an ideal gas from an initial volume ofVi to a final volume of Vf at constant temperature is given by the equation, S = R ln (Vf/Vi). What is the entropy change associated with the expansion of three moles of an ideal gas from an initial volume of Vi to a final volume of Vf at constant temperature?A) S = R ln (Vf/Vi)B) S = 3 mol R ln (Vf/Vi)C) S = R ln (Vf 23/Vi)D) S = R ln (Vf 3!/Vi)
Q:
What is k in Boltzmann's formula, S = k ln W?A) the degeneracy of the stateB) the equilibrium constant for the processC) the universal gas constant divided by Avogadro's numberD) the universal gas constant times Avogadro's number
Q:
An electron in an oxygen p orbital on which of the following would have the highest entropy?
A) CH3CH2OH
B) CH3CH2O"
C) CH3CO2OH
D) CH3CO2"
Q:
Which electron on an atom of copper would have the highest value of W in the Boltzmann formula?
A) 3s
B) 3d
C) 4s
D) 4p
Q:
What is W in Boltzmann's formula, S = k ln W?
A) a fraction indicating the probability of obtaining a result
B) a random number
C) the number of ways of obtaining the state
D) the work times Avogadro's number
Q:
The brown color associated with photochemical smog is due to NO2(g), which is involved in an equilibrium with N2O4(g) in the atmosphere.2 NO2(g) N2O4(g)Predict the signs of the enthalpy and entropy change for the forward reaction.A) The enthalpy change is negative and the entropy change is negative.B) The enthalpy change is negative and the entropy change is positive.C) The enthalpy change is positive and the entropy change is negative.D) The enthalpy change is positive and the entropy change is positive.
Q:
Sodium reacts violently with water according to the equation:2 Na(s) + 2 H2O(l) -> 2 NaOH(aq) + H2(g)The resulting solution has a higher temperature than the water prior to the addition of sodium. What are the signs of and for this reaction?A) H is negative and S is negative.B) H is negative and S is positive.C) H is positive and S is negative.D) H is positive and S is positive.
Q:
Predict the sign of S of the system for both of the following.I. 2 C(graphite) + O2(g) -> 2 CO(g)II. C4H10(g) -> C4H10(l)A) S should be negative for I and negative for II.B) S should be negative for I and positive for II.C) S should be positive for I and negative for II.D) S should be positive for I and positive for II.
Q:
For which process is the sign of S negative in the system?A) 2 H2(g) + O2(g) -> 2 H2O(g)B) 2 H2O(l) + 2 K(s) -> 2 K+(aq) +2 OH-(aq) + H2(g)C) H2O(s) -> H2O(g)D) H2O(l) -> H2O(g)
Q:
For which of the following will the entropy of the system increase?
A) condensation of steam
B) reaction of magnesium with oxygen to form magnesium oxide
C) reaction of nitrogen and hydrogen to form ammonia
D) sublimation of dry ice
Q:
Entropy is a measure of
A) free energy.
B) the heat of a reaction.
C) molecular randomness.
D) the rate of a reaction.
Q:
Which of the following processes is spontaneous?
A) a mixture of two gases separating into pure compounds
B) reaction of sodium with oxygen
C) precipitation of solute from a saturated solution
D) water flowing uphill
Q:
Which of the following processes are spontaneous?
I. dissolving more solute in an unsaturated solution
II. dissolving more solute in a saturated solution
III. dissolving more solute in a supersaturated solution
A) none of these
B) I
C) I and II
D) I, II, and III
Q:
The reaction A(g) -> B(g) is spontaneous under standard conditions. Which of the following statements must be true?I. The reaction B(g) -> A(g) is nonspontaneous under standard conditions.II. A(g) will be completely converted to B(g) if sufficient time is allowed.III. A(g) will be completely converted to B(g) rapidly.A) none of theseB) IC) I and IID) I, II, and III
Q:
Classify each of the following processes as spontaneous or nonspontaneous.I. H2O(l) -> H2O(g) T = 25C, vessel open to atmosphere with 50% relative humidityII. H2O(s) -> H2O(l) T = 25C, P = 1 atmA) I and II are both spontaneous.B) I is spontaneous and II is nonspontaneous.C) I is nonspontaneous and II is spontaneous.D) I and II are both nonspontaneous.
Q:
The chemical system shown below is at equilibrium. Which change in conditions will not result in a spontaneous forward reaction?N2(g) + 3 H2(g) 2 NH3(g) Kp = 4 105A) adding a catalystB) adding more H2C) adding more N2D) reducing the volume
Q:
Which forward reaction is a nonspontaneous process?
Q:
Which of the following statements is not true?
A) The reverse of a spontaneous reaction is always nonspontaneous.
B) A spontaneous process always moves toward equilibrium.
C) A nonspontaneous process cannot be caused to occur.
D) A highly spontaneous process need not occur rapidly.
Q:
What is the pH of the resulting solution if 25.00 mL of 0.10 M acetic acid is added to 10.00 mL of 0.10 M NaOH? Assume that the volumes of the solutions are additive. Ka = 1.8 10-5 for CH3CO2H
A) 9.43
B) 9.08
C) 4.92
D) 4.57
Q:
What is the approximate pH at the equivalence point of a weak acid-strong base titration if 25 mL of aqueous formic acid requires 29.80 mL of 0.3567 M NaOH? Ka =1.8 10-4 for formic acid.
A) 2.06
B) 5.48
C) 8.52
D) 11.94
Q:
What is the pH of a solution made by mixing 25.00 mL of 0.100 M HCl with 40.00 mL of 0.100 M KOH? Assume that the volumes of the solutions are additive.
A) 0.64
B) 1.64
C) 12.36
D) 13.36
Q:
What volume of 5.00 10"3 M HNO3 is needed to titrate 80.00 mL of 5.00 10"3 M Ca(OH)2 to the equivalence point?
A) 10.0 mL
B) 40.0 mL
C) 80.0 mL
D) 160. mL
Q:
What is the pH of a one liter solution that is 0.100 M in N and 0.100 M in NCl after 1.2 g of NaOH has been added? for N is 1.8 .
A) 9.52
B) 9.26
C) 9.62
D) 11.12
Q:
What is the [CH3CO2-]/[CH3CO2H] ratio necessary to make a buffer solution with a pH of 4.34? Ka = 1.8 10-5 for CH3CO2H.
A) 0.39:1
B) 0.91:1
C) 1.09:1
D) 2.5:1
Q:
What is the pH of a buffer system prepared by dissolving 10.70 grams of NH4Cl and 40.00 mL of 12 M NH3 in enough water to make 1.000 L of solution? Kb = 1.80 10-5 for NH3.
A) 8.88
B) 9.26
C) 9.64
D) 11.32
Q:
What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M methylamine, CH3NH2, with 20.00 mL of 0.10 M methylammonium chloride, CH3NH3Cl? Assume that the volume of the solutions are additive and that Kb = 3.70 10-4 for methylamine.
A) 10.17
B) 10.57
C) 10.97
D) 11.78
Q:
What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M NH3 with 5.00 mL of 0.10 M NH4Cl? Assume that the volume of the solutions are additive and that Kb = 1.8 10-5 for NH3.
A) 8.25
B) 10.26
C) 10.25
D) 11.13
Q:
What is the pH of a solution prepared by mixing 25.00 mL of 0.10 M CH3CO2H with 25.00 mL of 0.010 M CH3CO2Na? Assume that the volume of the solutions are additive and that Ka = 1.8 10-5 for CH3CO2H.
A) 2.87
B) 3.74
C) 4.75
D) 5.74
Q:
What is the hydronium ion concentration in a solution prepared by mixing 50.00 mL of 0.10 M HCN with 50.00 mL of NaCN? Assume that the volumes of the solutions are additive and that Ka = A) 1.5 10-10 M
B) 4.9 10-10 M
C) 1.6 10-9 M
D) 7.0 10-6 M
Q:
If solution (1) is a saturated solution of CaCO3, which of solutions (1)-(4) represents the solution after a small amount of K2CO3 is added and equilibrium is restored?A) (1)B) (2)C) (3)D) (4)
Q:
If solution (1) is a saturated solution of CaCO3, which of solutions (1)-(4) represents the solution after a small amount of Ca(NO3)2 is added and equilibrium is restored?
A) (1)
B) (2)
C) (3)
D) (4)
Q:
If solution (1) is a saturated solution of CaCO3, which of solutions (1)-(4) represents the solution after a small amount of HNO3 is added and equilibrium is restored?
A) (1)
B) (2)
C) (3)
D) (4)
Q:
The following pictures represent solutions of CaCO3, which may also contain ions other than Ca2+ and CO32- which are not shown. Gray spheres represent Ca2+ ions and unshaded spheres represent CO32- ions.If solution (1) is a saturated solution of CaCO3, which of solutions (1)-(4) represents the solution after a small amount of NaOH is added and equilibrium is restored?A) (1)B) (2)C) (3)D) (4)
Q:
If solution (1) is a saturated solution of AgCl, which of solutions (1)-(4) represents the solution after a small amount of NH3 is added and equilibrium is restored?A) (1)B) (2)C) (3)D) (4)
Q:
If solution (1) is a saturated solution of AgCl, which of solutions (1)-(4) represents the solution after a small amount of AgNO3 is added and equilibrium is restored?
A) (1)
B) (2)
C) (3)
D) (4)
Q:
If solution (1) is a saturated solution of AgCl, which of solutions (1)-(4) represents the solution after a small amount of HNO3 is added and equilibrium is restored?
A) (1)
B) (2)
C) (3)
D) (4)
Q:
The following pictures represent solutions of AgCl, which may also contain ions other than Ag+ and Cl- which are not shown. Gray spheres represent Ag+ ions and dotted spheres represent Cl- ions.If solution (1) is a saturated solution of AgCl, which of solutions (1)-(4) represents the solution after a small amount of HCl is added and equilibrium is restored?A) (1)B) (2)C) (3)D) (4)
Q:
If solution (1) is a saturated solution of CuS, which of solutions (2)-(4) are supersaturated?A) (2)B) (3)C) (4)D) none of the above
Q:
If solution (1) is a saturated solution of CuS, which of solutions (2)-(4) are saturated?
A) (2)
B) (3)
C) (4)
D) none of the above
Q:
If solution (1) is a saturated solution of CuS, which of solutions (2)-(4) are unsaturated?
A) only (2)
B) only (3)
C) only (4)
D) (3) and (4)
Q:
The following plot shows a titration curve for the titration of 1.00 L of 1.00 M diprotic acid H2A+ with NaOH. Which point a-d represents the isoelectric point?A) point aB) point bC) point cD) point d
Q:
What is the pH at the first equivalence point?
A) pH = pKa1
B) pH = 14 - pKa1
C) pH = (pKa1 + pKa2)/2
D) pH = pKa1 + pKa2
Q:
Which point a-d represents pKa2?
A) point a
B) point b
C) point c
D) point d
Q:
Which point a-d represents pKa1?
A) point a
B) point b
C) point c
D) point d
Q:
Which point a-d represents the second equivalence point?
A) point a
B) point b
C) point c
D) point d
Q:
Which point a-d represents the first equivalence point?
A) point a
B) point b
C) point c
D) point d
Q:
Which point a-d represents the H2X/HX- buffer region?
A) point a
B) point b
C) point c
D) point d
Q:
Which point a-d represents the HX-/X2- buffer region?
A) point a
B) point b
C) point c
D) point d
Q:
The following plot shows a titration curve for the titration of 1.00 L of 1.00 M diprotic acid H2A with NaOH.A buffer region is indicated by which point(s) a-d?A) point aB) points a and cC) point bD) points b and d
Q:
Which point a-d represents a buffer region?A) point aB) point bC) point cD) point d
Q:
Which points a-d represent the half-equivalence point and the equivalence point, respectively, for the titration of a weak acid?
A) points a and b
B) points a and c
C) points b and d
D) points c and d
Q:
At which point a-d is the pKa of the acid equal to the pH?
A) point a
B) point b
C) point c
D) point d
Q:
Which point a-d represents the equivalence point for the titration of a weak acid?
A) point a
B) point b
C) point c
D) point d
Q:
The following plot shows two titration curves, each representing the titration of 50.00 mL of 0.100 M acid with 0.100 M NaOH.Which point a-d represents the equivalence point for the titration of a strong acid?A) point aB) point bC) point cD) point d
Q:
What is the characteristic pH-titration curve for the titration of a weak acid by a strong base?A) AB) BC) CD) D
Q:
What is the characteristic pH-titrant curve for the titration of a strong base by a strong acid?A) AB) BC) CD) D
Q:
Use the graphs below to answer the following questions.What is the characteristic pH-titrant curve for the titration of a strong acid by a strong base?A) AB) BC) CD) D
Q:
Which picture represents the system with the lowest pH?A) (1)B) (2)C) (3)D) (4)
Q:
Which picture represents the system with the highest pH?
A) (1)
B) (2)
C) (3)
D) (4)
Q:
Which picture represents the system beyond the second equivalence point?
A) (1)
B) (2)
C) (3)
D) (4)