Download Chp 5 Circle the correct answer Consider three 1

Chp 5
Circle the correct answer
Consider three 1-L flasks at STP. Flask A contains NH3 gas, flask B contains NO2 gas, and flask C
contains N2 gas.
1.Which contains the largest number of molecules?
a)
b)
c)
d)
flask A
flask B
flask C
all are the same
2.In which flask are the molecules least polar and therefore most ideal in behavior?
a)
b)
c)
d)
flask A
flask B
flask C
all are the same
3.You have two samples of the same gas in the same size container, with the same pressure. The gas in
the first container has a kelvin temperature four times that of the gas in the other container.
The ratio of the number of moles of gas in the first container compared to that in the second is
a) 1 : 1
b) 4 : 1
c) 1 : 4
d) 2 : 1
4 A sample of oxygen gas has a volume of 4.50 L at 27C and 800.0 torr. How many oxygen molecules
does it contain?
a) 1.16  1023
b) 5.8  1022
c) 2.32  1024
d) 1.16  1022
5. The valve between a 5-L tank containing a gas at 9 atm and a 10-L tank containing a gas at 6 atm is
opened. Calculate the final pressure in the tanks.
a)
b)
c)
d)
3 atm
4 atm
7 atm
15 atm
6. What volume is occupied by 19.6 g of methane (CH4) at 27C and 1.59 atm?
a) 1.71 L
b) 18.9 L
c) 27.7 L
d) 302 L
7. You are holding two balloons, an orange balloon and a blue balloon. The orange balloon is filled
with neon (Ne) gas and the blue balloon is filled with argon (Ar) gas. The orange balloon has twice the
volume of the blue balloon. Which of the following best represents the mass ratio of Ne:Ar in
the balloons?
a) 1:1
b) 1:2
c) 2:1
d) 1:3
8. Hydrogen and chlorine gases react to form HCl. You and a friend are on opposite sides of a long
hallway, you with H2 and your friend with Cl2. You both want to form HCl in the middle of the room.
Which of the following is true?
a) You should release the H2 first.
b) Your friend should release the Cl2 first.
c) You both should release the gases at the same time.
d) You need to know the length of the room to answer this question.
9.
Which conditions of P, T, and n, respectively, are most ideal?
a)
high P, high T, high n
b)
low P, low T, low n
c)
high P, low T, high n
d)
low P, high T, low n
10. Four identical 1.0-L flasks contain the gases He, Cl2, CH4, and NH3, each at 0C and
1 atm pressure.
Which gas has the highest density?
11.
a) He
b) Cl2
c) CH4
d) NH3
For which gas do the molecules have the highest average velocity?
a) He
b) Cl2
c) CH4
d)
NH3
12,Which gas sample has the greatest number of molecules?
a) He
b) Cl2
c) CH4
d) NH3
e) all of the above
13. It is found that 250. mL of gas at STP has a mass of 1.00 g. What is the molar mass?
a) 89.6 g/mol
b) 28.0 g/mol
c) 14.0 g/mol
d) 22.4 g/mol
14. A 3.31-g sample of lead nitrate, Pb(NO3)2, molar mass = 331 g/mol, is heated in an evacuated
cylinder with a volume of 1.62 L. The salt decomposes when heated, according to the equation
2Pb(NO3)2(s)  2PbO(s) + 4NO2(g) + O2(g)
Assuming complete decomposition, what is the pressure in the cylinder after decomposition and
cooling to a temperature of 300. K? Assume the PbO(s) takes up negligible volume.
a)
b)
c)
d)
0.380 atm
0.228 atm
0.0342 atm
1.38 atm
15. Use the kinetic molecular theory of gases to predict what would happen to a closed sample of a gas
whose temperature increased while its volume decreased.
a) Its pressure would decrease.
b) Its pressure would increase.
c) Its pressure would hold constant.
d) The number of moles of the gas would decrease.
16. Which of the following would have a higher rate of effusion than C2H2?
a) N2
b) O2
c) Cl2
d)
CH4
17. Consider the following containers, one with helium at 27oC and the other with argon at 27oC.
Which of the following statements are true?
a) The speed of each atom of helium is 926 m/s.
b) The rms speed of the He and the Ar atoms are the same.
c) The average kinetic energy of the two samples are equal.
d)
All of the above are true.
18.
Two containers of Argon are shown below. The containers are at the same temperature.
Which of the following statements is false?
a) The rms velocity of Ar in both containers is the same.
b) The average kinetic energy of Ar in both containers is the same.
c) The force in which the Ar atoms collide with their container is the same in both
containers.
d) The frequency with which the Ar atoms collide with their container is the same in both
containers.
Chp 6
1. One mole of an ideal gas is expanded from a volume of 1.00 liter to a volume of 10.00 liters against
a constant external pressure of 1.00 atm. How much work (in joules) is performed on the
surroundings? (T = 300 K; 1 L atm = 101.3 J)
a) 456 J
b) 912 J
c) 2740 J
d) 2870 J
2. 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 (c = 0.20J/gC)
d)
Lead (c=0.14J/gC)
3. Which of the following properties is (are) intensive properties?
I. mass
II. temperature
III. volume
IV. concentration
V. energy
a) I, III, and V
b) II only
c) II and IV
d) III and IV
e) I and V
4. The enthalpy of fusion of ice is 6.020 kJ/mol. The heat capacity of liquid water is
75.4 J/molC. What is the smallest number of ice cubes at 0C, each containing one
mole of water, necessary to cool 500. g of liquid water initially at 20C to 0C?
a) 1
b) 7
c) 14
d) 15
5. For a particular process q = –17 kJ and w = 21 kJ. Which of the following statements is false?
a) Heat flows from the system to the surroundings.
b) The system does work on the surroundings.
c) E = +4 kJ
d) The process is exothermic.
6. Consider the reaction
C2H5OH(l) + 3O2(g)  2CO2(g) + 3H2O(l), H = –1.37  103 kJ
When a 15.1-g sample of ethyl alcohol (molar mass = 46.1 g/mol) is burned, how much energy
is released as heat?
a) 0.449 kJ
b) 2.25 103 kJ
c) 4.49 102 kJ
d) 1.02 103 kJ
7. Consider the reaction:
C2H5OH(l) + 3O2(g)  2CO2(g) + 3H2O(l); H = –1.37  103 kJ
Consider the following propositions:
I. The reaction is endothermic
II. The reaction is exothermic.
III. The enthalpy term would be different if the water formed was gaseous.
Which of these propositions is (are) true?
a)
b)
c)
d)
I
II
11 and III
I, and II
8. Consider the following processes:
(1/2)A  B
3B  2C + D
E +A D
H (kJ/mol)
150.
–125.
350.
Calculate H for: B + D  E + 2C
a)
b)
c)
d)
325 kJ/mol
525 kJ/mol
–325 kJ/mol
–175 kJ/mol
9. Consider the following numbered processes:
I. A  2B
II. B  C + D
III. E  2D
H for the process A  2C + E is
a)
b)
c)
d)
H1 + H2 + H3
H1 + H2
H1 + H2 – H3
H1 + 2H2 – H3
10.According to the first law of thermodynamics, the energy of the universe is constant. Does this
mean that ΔE is always equal to zero?
a) Yes, ΔE = 0 at all times, which is why q = -w.
b) No, ΔE does not always equal zero but this is only due to factors like friction and heat.
c) No, ΔE does not always equal zero because it refers to the system’s internal energy which
is affected by heat and work.
d) No, ΔE never equals zero because work is always being done on the system or by the
system.
11.
Consider the following standard heats of formation:
P4O10(s) = –3110 kJ/mol
H2O(l) = –286 kJ/mol
H3PO4(s) = –1279 kJ/mol
Calculate the change in enthalpy for the following process:
P4O10(s) + 6H2O(l)  4H3PO4(s)
Chp 16
1.
For which process is S negative?
a)
b)
c)
d)
e)
evaporation of 1 mol of CCl4(l)
mixing 5 mL ethanol with 25 mL water
compressing 1 mol Ne at constant temperature from 1.5 atm to 0.5 atm
raising the temperature of 100 g Cu from 275 K to 295 K
grinding a large crystal of KCl to powder
2. In which reaction is S° expected to be positive?
a)
b)
c)
d)
e)
I2(g)  I2(s)
H2O(1) H2O(s)
CH3OH(g) + (3/2)O2(g)  CO2(g) + 2H2O(l)
2O2(g) + 2SO(g)  2SO3(g)
none of these
3. Which statement is true?
a) All real processes are irreversible.
b) 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 (a–d) are true.
4.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) H < 0
b) Suniv > 0
c) Ssys< 0
d) Ssurr > 0
e) none of these
5. Which of the following result(s) in an increase in the entropy of the system?
I.
II.
III.
IV.
V.
a)
b)
c)
d)
E)
(See diagram above.)
Br2(g)  Br2(l)
NaBr(s)  Na+(aq) + Br–(aq)
O2(298 K)  O2(373 K)
NH3(1 atm, 298 K)  NH3(3 atm, 298 K)
I
II, V
I, III, IV
I, II, III, IV
I, II, III, V
6.I F TWO PYRAMID-SHAPED DICE (WITH NUMBERS 1 THROUGH 4 ON THE SIDES) WERE
TOSSED, WHICH OUTCOME HAS THE HIGHEST ENTROPY?
a) The sum of the dice is 3.
b) The sum of the dice is 4.
c) The sum of the dice is 5.
d) The sum of the dice is 6.
E) THE SUM OF THE DICE IS 7
7. Which of the following shows a decrease in entropy?
a)
b)
c)
d)
e)
8.
precipitation
gaseous reactants forming a liquid
a burning piece of wood
melting ice
two of these
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.
e) None of these (a-d)
9.For the dissociation reaction of the acid HF
HF(aq)
H+(aq) + F–(aq)
S is observed to be negative. The best explanation is:
a)
b)
c)
d)
e)
This is the expected result since each HF molecule produces two ions when it dissociates.
Hydration of the ions produces the negative value of S.
The reaction is expected to be exothermic and thus S should be negative.
The reaction is expected to be endothermic and thus S should be negative.
None of these can explain the negative value of S.
10.The second law of thermodynamics states that
a)
b)
c)
d)
e)
the entropy of a perfect crystal is zero at 0 K.
the entropy of the universe is constant.
the energy of the universe is increasing.
the entropy of the universe is increasing.
the energy of the universe is constant.
11.Which of the following statements is always true for a spontaneous process?
I. Ssys > 0
II. Ssurr > 0
III. Suniv > 0
IV. Gsys > 0
a) I
b) III
c) IV
d) I and III
e) III and IV
12. The heat of vaporization for 1.0 mole of water at 100.°C and 1.0 atm is 40.6 kJ/mol. Calculate S
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
13. For the vaporization of a liquid at a given pressure: (Note: Answers c and d imply that G is zero at
some temperature.)
a)
b)
c)
d)
G is positive at all temperatures.
G is negative at all temperatures.
G is positive at low temperatures, but negative at high temperatures.
G is negative at low temperatures, but positive at high temperatures.
The following questions refer to the following reaction at constant 25°C and 1 atm.
2Fe(s) + (3/2)O2(g) + 3H2O(l)  2Fe(OH)3(s) H = kJ/mol
Substance
S° (J/mol K)
Fe(OH)3(s)
Fe(s)
O2(g)
H2O(l)
107
27
205
70
14. Determine Ssurr for the reaction (in kJ/mol K)
a)
b)
c)
d)
E)
3.14
0.937
0.378
1.31
2.65
15. Determine Suniv for the reaction (in kJ/mol K)
a)
b)
c)
d)
E)
16.
0.22
2.2
0.36
2.8
3.6
What must be true about G for this reaction?
a)
b)
c)
d)
e)
G = H
G = 0
G > 0
G < 0
G = Suniv
17.Which of the following is true for exothermic processes?
a) Ssurr < 0
b) Ssurr = –H/T
c) Ssurr = 0
d) Ssurr > 0
e) two of these
18.
In which case must a reaction be spontaneous at all temperatures?
a)
b)
c)
d)
e)
19.
H is positive, S is positive.
H = 0, S is negative.
S = 0, H is positive.
H is negative, S is positive.
none of these
Consider the dissociation of hydrogen:
H2(g)
2H(g)
One would expect that this reaction:
a)
b)
c)
d)
will be spontaneous at any temperature.
will be spontaneous at high temperatures.
will be spontaneous at low temperatures.
will not be spontaneous at any temperature.
E)WILL NEVER HAPPEN.
20–22. At 1 atm, liquid water is heated above 100°C.
20.Ssurr for this process is
a) greater than zero.
b) less than zero.
c) equal to zero.
d) More information is needed to answer this question.
e) None of these (a-d)
21.S for this process is
a) greater than zero.
b) less than zero.
c) equal to zero.
d) More information is needed to answer this question.
e) None of these (a-d)
22 . Suniv for this process is
a) greater than zero.
b) less than zero.
c) equal to zero.
d) More information is needed to answer this question.
e) None of these (a-d)
23–25. Given that Hvap is 52.6 kJ/mol, and boiling point is 83.4°C, 1 atm, if one mole of this
substance is vaporized at 1 atm, calculate the following:
23.
Ssurr
a)
b)
c)
d)
e)
-148 J/K  mol
148 J/K  mol
630 J/K  mol
–630 J/K  mol
0
24. S
a)
b)
c)
d)
e)
25.
a)
b)
c)
d)
e)
-148 J/K  mol
148 J/K  mol
630 J/K  mol
–630 J/K  mol
0
G
-148 J/K  mol
148 J/K  mol
630 J/K  mol
–630 J/K  mol
0
26. For a certain process at 355 K, G = -12.4 kJ and H = -9.2 kJ. Therefore, S for the process is
a) 0
b) 9.0 J/Kmol
c) -9.0 J/Kmol
d) -21.6 J/Kmol
e) 21.6 J/Kmol
27.Consider the freezing of liquid water at –10°C. For this process what are the signs for H, S, and
G?
H
S
G
a)
+
–
0
b)
–
+
0
c)
–
+
–
d)
+
–
–
e)
–
–
–
28.When a stable diatomic molecule spontaneously forms from its atoms, what are the signs of H°,
S°, and G°?
a)
b)
c)
d)
e)
H°
+
+
–
–
–
S°
+
–
+
–
–
G°
+
–
+
+
–
29.Consider the following processes:
I. Condensation of a liquid.
II. Increasing the volume of 1.0 mol of an ideal gas at constant temperature.
III. Dissolving an ionic solid in water.
IV. Heating 1.0 mol of an ideal gas at constant volume.
For how many of these is S positive?
a) 0
b) 1
c) 2
d) 3
e) 4
30 .The third law of thermodynamics states
a)
b)
c)
d)
e)
the entropy of the universe is increasing.
the entropy of the universe is constant.
the entropy is zero at 0 K for a perfect crystal.
the absolute entropy of a substance decreases with increasing temperature.
the entropy of the universe equals the sum of the entropy of system and surroundings.
31. The standard free energy of formation of AgCl(s) is –110 kJ/mol. G° for the reaction 2AgCl(s) 
2Ag(s) + Cl2(g) is:
a) 110 kJ
b) 220 kJ
c) –110 kJ
d) –220 kJ
e) none of these
32. For the reaction Cl2O(g) + (3/2)O2(g)  2ClO2(g),
H° = 126.4 kJ/mol and S° = –74.9 J/K mol. At 377°C, G° equals:
a) 98.3 kJ/mol
b) 77.8 kJ/mol
c) 175.1 kJ/mol
d) 51.5 kJ/mol
e) 157.3 kJ/mol
33. For which of the following processes would S° be expected to be most positive?
a)
b)
c)
d)
e)
O2(g) + 2H2(g)  2H2O(g)
H2O(l)  H2O(s)
NH3(g) + HCl(g)  NH4Cl(g)
2NH4NO3(s)  2N2(g) + O2(g) + 4H2O(g)
N2O4(g)  2NO2(g)
34. In which process is S expected to be positive?
a) A reaction which forms a solid precipitant from aqueous solutions.
b) An ideal gas being compressed at a constant temperature and against a constant pressure.
c) Water freezing below its normal freezing point.
d) A spontaneous endothermic process at a constant temperature and pressure.
e)None of these.
Consider the following system at equilibrium at 25°C:
PCl3(g) + Cl2(g)
PCl5(g)
for which
H° = –92.5 kJ at 25°C.
35.If the temperature of the system is raised, the ratio of the partial pressure of PCl5 to the partial
pressure of PCl3 will
a)
b)
c)
d)
e)
increase.
decrease.
stay the same.
impossible to tell without more information.
none of these
36. When some Cl2(g) is added at constant volume and temperature, the ratio of the partial pressure of
PCl5 to the partial pressure of PCl3 will
a)
b)
c)
d)
e)
increase.
decrease.
stay the same.
impossible to tell without more information.
none of these