A thermodynamically reversible process takes place infinitely fast.
C.
In a reversible process, the state functions of the system are always much greater than those of the surroundings.
D.
There is always more heat given off to the surroundings in a reversible process than in an unharnessed one.
E.
All statements are true.
3.
A 100-mL sample of water is placed in a coffee cup calorimeter. When 1.0 g of an ionic solid is added, the temperature decreases from 21.5°C to 20.8°C as the solid dissolves. For the dissolving of the solid
A.
DH > 0
B.
DSuniv > 0
C.
DSsys< 0
D.
DSsurr > 0
E.
none of these
4.
A mixture of hydrogen and chlorine remains unreacted until it is exposed to ultraviolet light from a burning magnesium strip. Then the following reaction occurs very rapidly:
H2(g) + Cl2(g) ® 2HCl(g)
DG = –45.54 kJ
DH = –44.12 kJ
DS = -4.76 J/K
Select the statement below that best explains this behavior.
A.
The reactants are thermodynamically more stable than the products.
B.
The reaction has a small equilibrium constant.
C.
The ultraviolet light raises the temperature of the system and makes the reaction more favorable.
D.
The negative value for DS slows down the reaction.
E.
The reaction is spontaneous, but the reactants are kinetically stable.
5.
Which of the following shows a decrease in entropy?
A.
precipitation
B.
gaseous reactants forming a liquid
C.
a burning piece of wood
D.
melting ice
E.
two of these
6.
A chemical reaction is most likely to be spontaneous if it is accompanied by
A.
increasing energy and increasing entropy.
B.
lowering energy and increasing entropy.
C.
increasing energy and decreasing entropy.
D.
lowering energy and decreasing entropy.
7.
Which of the following statements is always true for a spontaneous process?
I. DSsys > 0 II. DSsurr > 0 III. DSuniv > 0 IV. DGsys > 0
A.
I
B.
III
C.
IV
D.
I and III
E.
III and IV
8.
The heat of vaporization for 1.0 mole of water at 100°C and 1.0 atm is 40.6 kJ/mol. Calculate DS for the process H2O(l) ® H2O(g) at 100°C.
A.
109 J/K mol
B.
–109 J/K mol
C.
406 J/K mol
D.
–406 J/K mol
E.
none of these
9.
For the reaction A + B ® C + D, DH° = +40 kJ and DS° = +50 J/K. Therefore, the reaction under standard conditions is
A.
spontaneous at temperatures less than 10 K.
B.
spontaneous at temperatures greater than 800 K.
C.
spontaneous only at temperatures between 10 K and 800 K.
D.
spontaneous at all temperatures.
E.
nonspontaneous at all temperatures.
10.
In which case must a reaction be spontaneous at all temperatures?
A.
DH is positive, DS is positive.
B.
DH = 0, DS is negative.
C.
DS = 0, DH is positive.
D.
DH is negative, DS is positive.
E.
none of these
11.
Given the following data (DHf, S°, respectively) for N2O4 (l) –20 kJ/mol, 209 J/K × mol, and N2O4(g) 10 kJ/mol, 304 J/K × mol. Above what temperature (in °C) is the vaporization of N2O4 liquid spontaneous?
Answer:
12.
Given that DHvap is 45.7 kJ/mol, and boiling point is 72.5°C, 1 atm, if one mole of this substance is vaporized at 1 atm, calculate the following:
DSsurr
A.
132 J/K × mol
B.
–132 J/K × mol
C.
630 J/K × mol
D.
–630 J/K × mol
E.
0
13.
Given that DHvap is 45.7 kJ/mol, and boiling point is 72.5°C, 1 atm, if one mole of this substance is vaporized at 1 atm, calculate the following:
DG
A.
132 J/K × mol
B.
–132 J/K × mol
C.
630 J/K × mol
D.
–630 J/K × mol
E.
0
14.
As long as the disorder of the surroundings is increasing, a process will be spontaneous.
A.
True
B.
False
15.
Consider the freezing of liquid water at –10°C. For this process what are the signs for DH, DS, and DG?
DH
DS
DG
A.
+
–
0
B.
–
+
0
C.
–
+
–
D.
+
–
–
E.
–
–
–
16.
Given the following free energies of formation:
C2H2(g)
209.2 kJ/mol
C2H6(g)
–32.9 kJ/mol
calculate
Kp
at 298 K for C2H2(g) + 2H2(g) C2H6(g)
A.
9.07 ´ 10–1
B.
97.2
C.
1.24 ´ 1031
D.
2.72 ´ 1042
E.
None of these is within a factor of 10 of the correct answer.
17.
Given the following data, calculate the normal boiling point for formic acid (HCOOH).
HCOOH(l)
-410.
130.
HCOOH(g)
-363
251
A.
2.57 K
B.
1730°C
C.
388°C
D.
82°C
E.
115°C
18.
The acid dissociation constant for a weak acid HX at 25°C is 1.60 ´ 10–8. Calculate the free energy of formation for X–(aq) at 25°C. The standard free energies of HX(aq) and H+(aq) at 25°C are –211.5 kJ/mol and 0, respectively.
A.
–12.5 kJ/mol
B.
255 kJ/mol
C.
0
D.
–167 kJ/mol
E.
322 kJ/mol
19.
For the reaction Cl2O(g) + (3/2)O2(g) ® 2ClO2(g), DH° = 126.4 kJ/mol and DS° = –74.9 J/K mol. At 377°C, DG° equals:
A.
98.3 kJ/mol
B.
77.8 kJ/mol
C.
175.1 kJ/mol
D.
51.5 kJ/mol
E.
none of these
20.
Determine DG° for the following reaction: CH4(g) + 2O2(g) ® CO2(g) + 2H2O(l)
Substance
(kJ/mol)
CH4(g)
–50.7
O2(g)
0
CO2(g)
–394.4
H2O(l)
–237.4
A.
207.7 kJ
B.
106.3 kJ
C.
817.9 kJ
D.
130.4 kJ
E.
943.1 kJ
21.
When ignited, solid ammonium dichromate decomposes in a fiery display. This is the reaction for a "volcano" demonstration. The decomposition produces nitrogen gas, water vapor, and chromium(III) oxide. The temperature is constant at 25°C.
Cr2O3(g)
–1140
0.0812
H2O(l)
–242
0.1187
N2(g)
0
0.1915
(NH4)2Cr2O7
–22.5
0.1137
Determine DS° reaction (in kJ/mol × K).
A.
0.7421
B.
0.6412
C.
0.9892
D.
0.6338
E.
0.5461
22.
When ignited, solid ammonium dichromate decomposes in a fiery display. This is the reaction for a "volcano" demonstration. The decomposition produces nitrogen gas, water vapor, and chromium(III) oxide. The temperature is constant at 25°C.
Cr2O3(g)
–1140
0.0812
H2O(l)
–242
0.1187
N2(g)
0
0.1915
(NH4)2Cr2O7
–22.5
0.1137
Determine DG° (in kJ/mol).
A.
–6119.7
B.
–2274.7
C.
–3042.6
D.
–5419.3
E.
–1488.8
23.
Calculate Ksp for the salt NaCl at 25°C.
Na+(aq)
–262
Cl–(aq)
–131
NaCl(s)
–384
A.
40
B.
4
C.
1
D.
0.4
E.
0.04
24.
At 699 K, DG° = –23.25 kJ for the reaction
Calculate DG for this reaction if the reagents are both supplied at 10.0 atm pressure and the product is at 1.00 atm pressure.
A.
–3.5 kJ
B.
–36.6 kJ
C.
+36.6 kJ
D.
–50.0 kJ
E.
+50.0 kJ
25.
For which of the following processes would DS° be expected to be most positive?
A.
O2(g) + 2H2(g) ® 2H2O(g)
B.
H2O(l) ® H2O(s)
C.
NH3(g) + HCl(g) ® NH4Cl(g)
D.
2NH4NO3(s) ® 2N2(g) + O2(g) + 4H2O(g)
E.
N2O4(g) ® 2NO2(g)
26.
Which of the following statements is correct?
A.
The internal energy of a system increases when more work is done by the system than heat was flowing into the system.
B.
The internal energy of a system decreases when work is done on the system and heat is flowing into the system.
C.
The system does work on the surroundings when an ideal gas expands against a constant external pressure.
D.
All statements are true.
E.
All statements are false.
27.
A 40.2 g sample of a metal is heated to 99.3°C and then placed in a calorimeter containing 120.0 g of water (c=4.18J/g°C) at 21.8°C. The final temperature of the water is 24.5°C. Which metal was used?
A.
Aluminum (c=0.89J/g°C)
B.
Iron (c=0.45J/g°C)
C.
Copper (0.20J/g°C)
D.
Lead (c=0.14J/g°C)
28.
Based on the reaction shown below, what energy change occurs when 1.2 moles of methane reacts? CH4 + 4Cl2(g) ® CCl4(g) + 4HCl(g), DH = –434 kJ
A.
5.2 ´ 105 J are released.
B.
5.2 ´ 105 J are absorbed.
C.
3.6 ´ 105 J are released.
D.
3.6 ´ 105 J are absorbed.
E.
4.4 ´ 105 J are released.
29.
Given the equation S(s) + O2(g) ® SO2(g), DH = –296 kJ, which of the following statement(s) is (are) true? I. The reaction is exothermic. II. When 0.500 mole sulfur is reacted, 148 kJ of energy is released. III. When 32.0 g of sulfur are burned, 2.96 ´ 105 J of energy is released.
A.
All are true.
B.
None is true.
C.
I and II are true.
D.
I and III are true.
E.
Only II is true.
30.
Consider the following processes:
2A ® 1/2B + C
DH1 = 5 kJ/mol
(3/2)B + 4C ® 2A + C + 3D
DH2 = –15 kJ/mol
E + 4A ® C
DH3 = 10 kJ/mol
Calculate DH for: C ® E + 3D
A.
0 kJ/mol
B.
10 kJ/mol
C.
–10 kJ/mol
D.
–20 kJ/mol
E.
20 kJ/mol
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(kJ/mol)
Calculate DG for this reaction if the reagents are both supplied at 10.0 atm pressure and the product is at 1.00 atm pressure.
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