H= qp0 E=qo

Principles of Chemistry
Mid-term exam (II)
11/3/2021

Q1 (2 points each)
1. Negative temperatures are impossible on the Kelvin
A scale (K), an absolute thermodynamic temperature
scale.
(a) True
(b) False
2. A thermodynamic state function is a physical quantity

B whose value depends on path.

(a) True
(b) False

B
3. For a closed system, irreversible reaction does not
follow first law of thermodynamics.
…

(a) True GThe of theuniveBe13onseant

ehergy
.

(b) False
4. The heat (q) measured in a bomb calorimeter (Hint:
constant volume) is equal to change of enthalpy (DH).
B
⼀
Δ
~~ m

(a) True
oH
=

E PV
- .

(b) False
5. Gibbs free energy can be used to predict the direction
of a reaction, but not the rate of a reaction.
A (a) True
(b) False

Q2 (3 points each)
1. Object A is placed next to Object B so that they are
 touching. Heat will transfer from one to another to

B reach thermal equilibrium. Which of the following

statements is true?
(a) Transfer of heat is based on the internal energy of
objects.
(b) Transfer of heat is based on the temperature of
objects.
(c) Transfer of heat is based on the heat capacity of
objects.
(d) Transfer of heat is based on the amount of heat
containing in the objects. 0
E nCuoT
=

0
2. When heating a balloon containing ideal∞ gas at 1 atm,
a scientist detects a temperature
~
increase in the

B
balloon. Which of the following statements accurately
characterizes the gas in the balloon during this period?
~

(a) The internal energy of balloon has no change.

(b) The velocity of molecules in the solution is
increasing.
、(c) No work has been done for this process.
、(d) The entropy of the gas is decreasing. 定温 。

_
3. In a system undergoing isothermal expansion
involving ideal gas, what are the values of internal

B… energy and work done on the system if heat transfers

to the system is 500 J?
~

(a) internal energy is 0 J, and work is 500 J. =

(b) internal energy is 0 J, and work is –500 J.
(c) internal energy is 500 J, and work is 0 J.
(d) internal energy is –500 J, and work is 0 J.
4. For two different paths (1 and 2) from point A to B,

oHenpy
enthalpy change ( H) is
 (a) H1 > H2
(b) H1 < H2
(c) H1 = H2
5. What is the net work done on the gas as it goes from
point E to D and then to C on the Pressure vs Volume
c diagram? (Pa ´ m = J)
3

P V
. -
…

500-
+ .
.

( 7

loo

(a) 0 ∞
(b) 500 J
(c) –500 J
(d) 600 J

召
6. Suppose that 500 J of heat is transferred to 1.00 mol
idea gas (at 298 K, 1 atm). What will the final
temperature T be if the heat is transferred at constant
f

~ volume?
(a) 313 K = CE = AxCUx , O= 3x 8 31401
qu T 5

(b) 308 K
.

K
0

(c) 347 K
(d) 338 K
K * oT =

Ʃ0
T 40 =

7. The temperature of∞ 2.00 mol Ne(g) is increased from

~
25 °C to 200 °C at constant pressure. Calculate the
8
)
=

) nculn (a serx ×8314 x 2 n "

— (
 change in the entropy of neon (assume ideal behavior).
B (R = 8.314 J/mol-K)
(a) 11.5 J/K
(b) 19.2 J/K
(c) 86.5 J/K
(d) 8.3 J/K
8. For combustion
…
of butane at 1 atm,
2 C H (g) + 13 O (g) → 8CO (g) + 10 H O (l) ΔH =
A
4 10 2 2 2

-5757 kJ
The value of internal energy (ΔE) is 5 R
(a) > ΔH > 5

M
nCpolE .
θ^
。

(b) = ΔH =

(c) < ΔH
(d) zero ,
= naoT
θ
9. Which of the following pairs makes a correct
O

comparison between the standard entropies of the

D
~
following compounds at 25 C? o

(a) He > N 2

、(b) NaCl (s) > NaCl (aq)

(c) Al > Al O
2 3

(d) C (s, graphite) > C (s, diamond)

10. For a chemical reaction to be . not spontaneous at all

mgiot
temperatures, which of the following conditions must

. .
be met?
pes .
D
-
(a) S > 0, H > 0 o

(b) S > 0, H < 0 o P

?
.

(c) S < 0, H < 0

(d) S < 0, H > 0
11. For the reaction at 25 C and 1 atm.
o

片以酱⼀
D 2 NO (g)→2 NO(g) + O (g) ΔH = 112 kJ
2

Calculate0 ΔS(surr).
2

(a) 4480 J/K

 (b) 375.8 J/K
(c) –4480 J/K
(d) –375.8 J/K
0
12. For the combustion of acetylene at 25 C and 1 atm, o

2 C H (g) + 5 O (g) 4 CO (g) + 2 H O(g)

D
2 2 2 2 2

ΔS = –194.6 J/K and ΔH = –2511.2 kJ

Calculate ΔS (universe).
(a) –8232.6 J/K
- 194 . 6 o
⼀毕
(b) 8232.6 J/K
(c) 8621.4 J/K + θ

(d) –8621.4 J/K oG H TS

oHo =<
-

.
.

13. When water freezes in a glass beaker spontaneously,

∞
which of the following statements is correct?
(a) ΔS (system) decreases but ΔS (surroundings)
c remains the same.
(b) ΔS (system) decreases and ΔS (surroundings) also
decreases.
(c) ΔS (system) decreases but ΔS (surroundings)
increases.
(d) ΔS (system) increases and ΔS (surroundings) also
increases.
-
14. When an ideal gas is expanded (a) reversibly or (b)

B
irreversibly from volume V to V . Which of the i f

following statements
maximum
is true?
→
.

(a) w (reversible) > w (irreversible)

(b) w (reversible) < w (irreversible)
(c) w (reversible) = w (irreversible)
(d) w (reversible) = w (irreversible) + PΔV
15. For the following reaction at 25 C, o

C 3 C (s) + 4 H (g)® → C H (g) Δ DH = 103.8 kJ o

2 3 8

and DS
Δ = -269 J/K
o

H Togo
0

G
0

Calculate ΔDG . o 0 =
0 -

l 03 . 8× 103 -

293 × (
-

269 )
 (a) +104.1 kJ
(b) +110.5 kJ
(c) +184.0 kJ
(d) –23.6 kJ
16. Consider the system at 25 C, oCGO

B?
A (g)® B (g) G = 8996 J/mol and G = 11718 J/mol
o
A
o
B

Which one of the following is true?

24 nn 5 yzxluk
(a) The reaction is spontaneous. 27 2
r .

v
- .

(b) Equilibrium constant for this reaction is 0.333

δ
(c) DH > 0
'

(k) 11 M 18 89962 8 314 298xhl)

0

0 G krln ×
-

≡ .
-

(d) DS > 0 ,

0 17. A gas 0
⑧ expands adiabatically and reversibly (V2 >
~

V1). ΔH is nGoT
再 q绝熱
園
=

(a) less than zero. 些

(b) equal to zero. (P )

oHroktoHenpof
<
-

(c) greater than zero. ”

ω
(d) More information is needed. ∴ PoV
的~
18. A gas expands isothermally and reversibly (V2 >
V1). 。 S is
c (a) less than zero.
定 。

(b) equal to zero. oS nRln =

(÷ )
(c) greater than zero.
(d) More information is needed.

B
19. Consider the figure below which shows o G f for a
chemical process plotted against absolute temperature.
Which one of the following is not true, based on the
information in the diagram?

w sd
oG ' ro 1 -7 i

.
%
 v H >0
(a)
、 (b) S < 0
(c) The reaction is spontaneous at high temperatures.
(d) There exists a certain temperature at which H =
T S
20. A research group decides to study the
thermodynamics of the dissolution of borax.
Na B O (OH) ⋅8 H2O (s) 2 Na (aq) +
2 4 5 4
+

B O (OH) (aq) +8 H O (l)

4 5 4
2−
2

By determining the molar solubilities and solubility

product constant at different temperatures, the group is
able to determine the various thermodynamic
parameters. Their results are shown in the following
graph:

k THoS
)

-
- ( lnk .

RTlnk
c
0

G
,

0
-
=

,
+= lnk
Which of the following statement for the data plotted
in the graph is ∞
incorrect?
(a) The slope of the graph can be used to
calculate ∆H . o

(b) The y-intercept of the graph can be used to

calculate ∆S . o

(c) The x-intercept of the graph can be used to

calculate ∆G . o

oTosoiksowC
(d) The graph will not pass original point.
21. For the reaction, A + B C, ∆H = +30 kJ; ∆S = o o

+50 J/K.
iHcw .
 Therefore, the reaction is:
(Assume ∆H and ∆S remain the same as the change of
temperature)
(a) spontaneous at all temperatures.
(b) nonspontaneous at all temperatures.
(c) spontaneous at temperatures greater than 600 K.
(d) spontaneous only at 25 C.
o

22. The entropy will usually increase when

⑥⑨

猖
I. two or more smaller molecules are formed into a
molecule.
II. a reaction occurs that results in an increase in the
number of moles of gas.

λIII. liquid changes to solid.

IV. gas changes to liquid.
(a) I only
(b) II only
(c) III only
(d) IV only
0
。
23. For a certain process, at 313 K, ΔG = –30.0 kJ. If the
process is carried out ∞reversibly, what is the amount of
ONA useful work that is impossible to be performed?
(a) 0
(b) 10 kJ 76 T
44 12 4
-
+ . .

(c) 30 kJ
n 7 " n 6)
.w

049
(d) 35 kJ oG
-

l
24.
* A mixture of hydrogen and chlorine remains

o
7
unreacted until it is exposed to ultraviolet light from a
⼀

burning magnesium strip. Then the following reaction

occurs very rapidly. H (g) + Cl (g)→2HCl (g) G = –
2 2
o

45.54 kJ, ΔH = –44.12 kJ, ΔS = –4.76 J/K. Select the

o o

statement below that best explains this behavior.

(a) The ultraviolet light raises the temperature of the
system and makes the reaction more favorable.
 dunare thermodynamically more stable
(b) The reactants
和

的 _
s版
than the products.
(c) The reaction has a small equilibrium constant.
(d) The reaction is spontaneous, but the reactants are
→kinetically討論反應
stable. 的

v. 友慢→ reaclanemoabe
25. In a Zn-Ag battery, the following reaction is carried 。

B out:
Zn (s) + 2 Ag (aq)→Zn (aq) + 2 Ag (s).
+ 2+

For such a cell, E° is 1.56 V. Calculate G° at 25°C.

(F = 96500 Coulombs)
(a) 151 kJ 0

(b) –301 kJ Ge
0 nFE -

(c) –151 kJ e 296w ×1 56

-
,

(d) –75 kJ
.

~
26. Consider 1.00 mole of an ideal gas that is expanded
isothermally at 25°C from0 2.45 ´ 10 atm to 9.87 ´ 10 -2 -3

1y
atm. Which one of the following is correct?
(a) q = -1480 J =… 1010 q9
U
~

(b) w = 1480 J xl 0

(c) S = 7.56 J/K

(d) G = 2250J Vi
= . 082
—
k8 0
47 5 ,
=
.

q 87 10
,

×
27. At 298 K, the standard enthalpies of formation for

B
C H (g) and C H (l) are 227 kJ/mol and 49 kJ/mol,
2 2 6 6

respectively. Calculate H for C H (l) 3 C H (g).

o
6 6 2 2

(a) 178 kJ
(b) 632 kJ
(c) 276 kJ
GHo → 3 GHr

(d) -178 kJ 3× 22 ) 49 -
,
-

28. All of the following have a standard heat of

formation value of zero at 25 C and 1.0 atm except:
D
o

(a) N (g) 2

(b) He (g)
 (c) Fe (s)
(d) Hg (g)
29. A cylinder confines 2.00 L gas under a pressure of
1.00 atm. The external pressure is also 1.00 atm. The
gas is heated slowly, with the piston sliding freely
…
~

outward to maintain the pressure of the gas close to

1.00 atm. Suppose the heating continues until a final
volume of 3.50 L is reached. Calculate the work done
on the gas.
(a) -152 J w Pol =

(b) -112 J
(c) -172 J 1 × 1 . 5 × 01 .
-
l
3

(d) -132 J
30. The standard heat of combustion of ethanol, C H OH
2 5

D (MW = 46.0), is 1372 kJ/mol ethanol. How much heat

(in kJ) would be liberated by completely burning a
20.0 g sample?
(a) 686 kJ
(b) 519 kJ
1372 ×
昆 ,

(c) 715 kJ
(d) 597 kJ

Equations:
E=q+w
H = E + PV
w = – nRTln(V2 /V1)
rev

E = nC T = q (constant volume)
v v

H = nC T = q (constant pressure)
p p

Cv=3R/2 Monatomic ideal gas

Cp=5R/2 Monatomic ideal gas
Cp=Cv+R All ideal gas
S = nR ln(V2 /V1) = q / T
rev
 S ® = nC ln (T2/T1) (constant volume)
T1 T2 v

S ® = nC ln (T2/T1) (constant pressure)

T1 T2 p

S = – H/T (constant pressure; only PV work is

surr

allowed)
G= H–T S
G = Gº + RT ln (Q) (Q is the reaction quotient)
ln (K) = – ( Hº/R)(1/T) + Sº/R
ln (K /K ) = – ( Hº/R)(1/T – 1/T )
2 1 2 1

Gº = – nFεº = – RT ln Keq
Consider the reduction half-reaction: E = Eº –
(0.0592/n) log (Q)
Atm L = 1013.2 J
R = 8.314 J/mole K