Thermodynamics, laws of thermodynamics, thermo chemistry

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THERMODYNAMICS CHEMISTRY
PP
Practice Questions
EXERCISE - I
(Single & One or More than One Correct Answers)
1. 1 g H2
gas as STP is expanded so that volume is doubled. Hence, work done is
a) 22.4 L atm b) 5.6 L atm c) 11.2 L atm d) 1.135 K Joule
2. If x and y are two intensive variables then :
a) xy is an intensive variable b) x/y is an intensive variable
c) (x+y) is an intensive variable d) dx/dy is an extensive property
3. In a process a system does 140 J of work on the surroundings and only 40 J of heat is added to the
system, hence change in internal energy is
a) 180 J b) –180 J c) -23.92 Cal d) –100 J
4 A substance mass 10 kg at height of 10m is allowed to fall. At place where kinetic energy is 200 J
potential energy is
a) 580 J b) 780 J c) 186.6 Cal d) 350 Cal
5 Number of phases present in the following thermodynamic systems are :
1)      4 3 2NH HS s NH g H S g 2)      3 2CaCO s CaO s CO g
3)    2 2 3N g 3H 2NH g 
a) 2, 3, 1 b) 3, 2, 1 c) 1, 2, 3 d) 3, 1, 2
6. Two mole of an ideal gas is heated at constant pressure e of one atmosphere from 27 C
to 127 C.
If Cv, m
= 20 + 10–2
T JK–1
mol–1
, then q and U for the process are respectively.
a) 6362.8 J, 4700 J b) 1522.2 Cal, 1124.4 Cal
c) 7062.8, 5400 J d) 3181.4 J, 2350 J
7. Which of the following is /are true in the case of an adiabatic process
a) q = W b)  U q c) q = 0 d)  U W .
8. In the isothermal expansion of an ideal gas :
a)   0U b)   0T c)  0q d) W q .
9. During the isothermal expansion of an ideal gas :
a) the internal energy remains unaffected b) the temperature remains canstant
c) the enthalpy remains unaffected d) the enthalpy becomes zero.
10 Assuming that, water vapour is an ideal gas the internal energy change  U when 1 mol of water
is vaporised at 1 bar pressure and 1000
C (given : molar enthalpy of vaporisation of water at 1 bar
and 373K = 41 kJ mol–1
and R = 8.3 J K–1
mol–1
) will be
a) 41.00 kJ mol–1
b) 4.100 kJ mol–1
c) 3,7904 J mol–1
d) 37.904 kJ mol–1

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11. 1 mole of an ideal gas A(Cv,m
= 3R) and 2 mole of an ideal gas B are ,
3
2
 
  v mC R taken in a
container and expanded reversible and adiabatically from 1 lire to 4 litre starting from initial
temperature of 320 K. E or U for the process is
a) – 240 R b) 240 R
c) -1920 Cal mole–1
K–1
d) – 960 R
12. For polytropic process PVn
= constant, Cm
(molar heat capacity) of an ideal gas is given by
a)  v,m
R
C
n 1

 b)  v,m
R
C
1 n

 c) v,mC R d)  p,m
R
C
n 1


13. 2 mole of an ideal mono atomic gas undegoes a reversible process for which PV2 = C. The gas is
expanded from initial volume of 1 L to final volume of 3 L starting from initial temperature of
300 K. Find H for the process :
a) – 600 R b) – 1000 R
c) – 3000 R d) – 2 k Cal mole–1
K–1
14 For gaseous reaction, if H is the change in enthalpy and U that in internal energy then :
a) H is always greater than U b) H is always less than U
c) H < U only if the number of mole of the products is less than that of the reactants
d) U < H only if the number of mole of the reactants is less than that of the products
15. Which has / have a positive value(s) of H ?
a) H2(g)  2H(g)
b) H(g)  H+
(g)
+ e
c) H2
O(l)  H2
O(g)
d) H+
(aq)
+ OH–
(aq)  H2
O
16. The value of H U   for the following reaction at 270
C will be :      3 g 2 g 2 g2NH N 3H 
a) 8.314 x 273 x (–2) J b) 8.314 x 300 x (–2) J
c) -600 R d) 8.314 x 300 x 2 J
17. Which of the following reactions have same heat of reaction at constant temperature and at constant
volume?
a) H2(g)
+ Cl2(g)
 2HCl(g)
b) 2NO(g)
 N2(g)
+ O2(g)
c) CO3
O4(s)
+ 4CO(g)
 3CO(s)
+ 4CO2(g)
d)      2 2 3N g 3H g 2NH g 
18 When 1.0 g of oxalic acid (H2
C2
O4
) is burned in a bomb calorimeter whose heat capacity is 8.75 kJ/
K, the temperature increases by 0.312 K. The enthalpy of combustion of oxalic acid at 27 C
a) –245.7 kJ/mol b) –244.452 kJ/mol c) –246.947 kJ/mol d) -58.85 k Cal mol-1
19. The molar heat capacities at constant pressure (assumed constant with respect to temperature) at A,
B and C are in ratio of 3 : 1.5 : 2.0. The enthalpy change for the exothermic reaction A + 2B  3C
at 300K and 310K is 300H and 310H respectively then :
a) 300 310H H   b) 300 310H H   c) 300 310H H  
d) If T2
>T1
then 310 300H H   and if T2
< T1
then 310 300H H  

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20. The bond dissociation energies for Cl2
, I2
, and ICl are 242.3, 151 and 211.3 kJ/mol respectively.
The enthalpy of sublimation of iodine is 62.8 kJ/mol. What is the standard enthalpy of formation of
ICl(g)
?
a) –211.3 kJ/mol b) 4019 Cal/mol c) 16.8 kJ/mol d) 33.5 kJ/mol
21. The amount of heat released, when 20 mL of 0.5 M NaOH is mixed with 100 mL of 0.1 M HCl, is
x kJ. The heat of neutralization is
a) 10 x k Cal mole–1
b) 100 x kJ mole–1
c) - 100 x kJ mole–1
d) -23.92 k Cal mole–1
22. Enthalpy of neutralization of 3 3H PO acid is –106.68 kJ/mol using NaOH. If enthaly of neutralization
of HCl by NaOH is –55.84 kJ/mol. Calculate ionizationH of H3
PO3
into its ions
a) 50.84 kJ/mol b) 5 kJ/mol c) 2.5 kJ/mol d) 5000 J/mol
23 Consider the following data :  f 2 4H N H , 50 kJ/ mol, 
l  f 3H NH ,g 46 kJ/ mol,  
B.E. (N–H) = 393 kJ/mol and B.E. (H–H) = 436 kJ/mol, also  vap 2 4H N H , 18 kJ / mol l
The N–N bond energy in N2
H4
is
a) 226 kJ/mol b) 154 kJ/mol c) 190 kJ/mol d) 45.45 k Cal/mole
24. What is the bond enthalpy of Xe–F bond ?
         4 2XeF g Xe g F g F g F g ; 
    rH 292 kcal/ mol 
Given that I.E of Xenon = 279 k Cal / mole, B.E of F2
= 38 k Cal / mol, E.A of F = 85 k Cal / mole.
a) 24 k Cal/mol b) 34 k Cal/mol c) 8.5 k Cal/mol d) 142.12 kJ/mole
25 Which has maximum entropy change of vaporisation ?
a) water (l) b) toluene (l) c) diethyl either (l) d) acetone (l)
26. What are the signs of the entropy change (+ or –) in the following :
I : A liquid crystallises into a solid
II : Temperature of a crystalline solid is raised from 0 K to 115 K
III : 2 NaHCO3
(s)         2 3 2 3 2 2Na CO s Na CO s CO g H O g   IV :    2H g 2H g
I II III IV I II III IV
a) – + + + b) – – – +
b) – – – + d) + – – –
27. When charcoal burns in air signs of H and S are : 2C(s)
+ O2(g)  2CO(g)
H S H S H S H S
a) – – b) – + c) + + d) + –
28. When a liquid evaporates, which is true about the signs of the enthalpy and entropy changes ?
H S H S H S H S
a) + + b) – – c) + – d) – +

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29. Considering entropy(s) at a thermo dynamic parameter, the criterion for the spontanity of any process
is
a) system surroundingsS S 0    b) system surroundingsS S 0   
c) systemS 0  only d) surroundingsS 0  only
30. Calculate S for 3 mole of a diatomic ideal gas which is heated and compressed from 298 K and 1
bar to 596 K and 4 bar.
a) –14.7 cal K–1
b) +14.7 cal K–1
c) –4.9 cal K–1
d) 6.3 cal K–1
31. One mole of an ideal monoatomic gas at 270
C is subjected to a reversible isoentropic compression
until final temperature reached to 3270
C If the initial pressure was 1.0 atm then find the value of In
P2
:
a) 1.75 atm b) 0.176 atm c) 1.0395 atm d) 2.0 atm
32. Two mole of an ideal gas is expanded irreversibly and isothermally at 370
C until its volume is
doubled and 3.41 kJ heat is absorbed from surroundings. totalS (system + surroundings) is
a) – 0.52 J/K b) 0.52 J/K c) 22.52 J/K d) 0
33. For a perfectly cyrstalline solid 3
p,mC aT bT,  where a and b are constant. If p,mC is 0.40 J/K mol
at 10K and 0.92 J/K mol at 20 K, then molary entropy at 20 K is :
a) 0.92 J/K mol b) 8.66 J/K mol c) 0.813 J/K mol d) None of these
34. If the inversion temperature of a gas is –800
C, then it will produce cooling under Joule-Thomson
effect at
a) 298 K b) 273 K c) 193 K d) 173 K
35 Which of the following does not have zero entropy even at absolute zero ? CO, CO2
, NaCl, NO
a) CO, CO2
b) CO, NO c) CO2
, NaCl d) NaCl
36. Combustion of sucrose is used by aerobic organisms for providing energy for the life susting
processes. If all the capturing from the reaction is done through electrical process (non P–V work)
then calculate maximum available energy which can be captured by combustion of 34.2gm of
sucrose
Given : 
  1
( ) 6000combustionH sucrose kJ mol
 180 /combustionS J K mol and body temperature is 300 K.
a) 600 kJ b) 594.6 k Cal c) 144.83 k Cal d) 605.4 kJ
37. If G H T S     and
 
P
d G
G H T
dT
  
     
 
then variation of emf of a cell E, with temperature
T is given by :
a)
H
nF

b)
G H
nFT
 
c)
S
nF

d)
S
nF


38. For A B, H   3.5 kcal mol–1
, S = 10 cal mol–1
K–1
. Reaction is spontaneous when temperature can
be
a) 400 K b) 270
C c) 770
C d) 350 K

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39. Sign of G for the melting of ice is negative at
a) 265 K b) 270 K c) 277 K d) 274 K
40. Driving force of a reaction is the
a) resultant of enthalpy and entropy change
b) resultant of enthalpy and internal energy change
c) resultant of entropy and internal energy change
d) term concerned with change in free energy
41. G 
for the reaction x y z  is –4.606 kcal. The value of equilibrium constant of the reaction at
2270C is
a) 100 b) 10 c) 2 d) 0.01
42. Which of the following is true for spontaneous process ?
a) G > 0 b) G < 0 c) G = 0 d) G = TS
43 Which of the following expressions is correct ?
a) G nFE    b) G nFE   
c) cellG 2.303RTnFE    d) cG nF log K  
44 In the conversion of lime stone to lime, CaCO3(s)  CaO(s)
+ CO2(g)
the values of Ho
and So
are
+179.1 kJ mol–1
and 160.2 JK–1
mol–1 respectively at 298 K and 1 bar. Assuming , Ho
and So
do
not change with temperature; temperature above which conversion of lime stone to lime will be
spontaneous is
a) 1118 K b) 1008 K c) 1200 K d) 845 K
45. For H2
O(l)
(1 bar, 373K)  H2
O(g)
(1 bar, 373K). The correct set of thermodynamic parameters is
a) G = 0, S = + ve b) G = 0, S = – ve
c) G = +ve, S = 0 d) G = –ve, S = +ve
46 For the hypothetical reaction A2(g)
+ B2(g)
 2AB(g)
rG 
and rS 
are 20 kJ/mol and –20 JK–1
mol–1
respectively at 200 K.
If r pC is 20 JK–1
mol–1
then r H 
at 400 K is
a) 20 kJ/mol b) 7.98 kJ/mol c) 28 kJ/mol d) None of these
47 Calculate rG 
for (NH4
Cl, s) at 310 K.
Given : 0
f H for 4 r p(NH Cl,s) 314.5KJ / mol; C 0   
   2 2
0 1 1 0 1 1
N g H gS 192JK mol ; S 130.5JK mol ;   
     2 4
0 1 1 0 1 1
Cl g NH Cl sS 233JK mol ; S 99.5JK mol   
 
All given data at 300 K.
a) –198.56 kJ/mol b) –426.7 kJ/mol c) –202.3 kJ/mol d) None of these

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EXERCISE - II
(Linked Comprehension type questions)
Passage - I
Chemical reactions are invariably associated with the transfer of energy either in the form of heat or
light. In the laboratory, heat changes in physical and chemical processes are measured with an instrument
called calorimeter. Heat change in the process is calculated as : q = ms  T; s = Specific heat = c  T
c = Heat capacity. Heat of reaction at constant ressure is measured using simple or water calorimeter.
qv =  U = Internal energy change. Heat of reaction at consant pressure is measured using simple or
water calorimeter. qp
=  H ; Qp
= qv + P  V and  H =  U +  nRT. The amount of energy
released during a chemical change depends on the physical state of reactants andproducts, the condition
of pressure, temperature and volume at which the reaction is carried out. The variation of heat of
reaction with temperature and pressure is given by Kirchhoff’s equation :
2 1
p
2 1
H H
C ;
T T
  
 

2 1
2 1
U U
C
T T
  
 

v
(At constant pressure) (At constant volume)
48. The enthalpy of fusion of ice is 6.02 kJ mol–1
. the heat capacity of water is 4.18 J g–1
C–1
. What is the
smallest number of ice cubes at 00
C each containing one mole of water, that are needed to cool 500g
of liquid water from 200
C to 00
C ?
a) 1 b) 7 c) 14 d) 125
49. The enthalpy change  H for the reaction.      2 2 3N g 3H g 2NH g  is –92.38 kJ at 298 K. The
internal energy change U at 298 K is
a) –92.38 kJ b) –87.42 kJ c) 97.34 kJ d) –89.9 kJ
50 The specific heat of I2
in vapour and solid state are 0.031 and 0.055 cal/g respectively. The heat of
sublimation of iodine at 2000
C is 6.096 kcal mol–1
. The heat of sublimation of iodine at 2500
C will be
a) 3.8 kcal mol–1
b) 4.8 kcal mol–1
c) 2.28 kcal mol–1
d) 5.8 kcal mol–1
Passage - II : Consider the following energy level diagram :
Energy
O
6 12 6 2C H O +6O (g)
2 26CO ( ) 6 ( )g H O l
x
y z
2 26C(s)+6H (g)+9O (g)
Answer the following question on the basis of the given diagram :
51. The heat of formation of glucose is
a) –x b) –y c) x – y d) –x + z
52 In the given diagram z refers are
a) 2fCO6 x H 
b) 6 12 6fC H OH 
c) 6 12 6combustion C H OH 
d)  6 2
combustion C fH O iH H   

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53 The quantity y is equal to
a)    2combustion C s combustion H gH H   b) x + z
c) x –z d) 2 2fCO H OH H  
PASSAGE -III
The bond dissociation energy depends upon the nature of the bond and nature of the molecule. If any
molecule morethan 1 bonds are present of similar nature then the bond energy reported is the average
bond energy.
54 Determine C-C and C-H bond enthalpy (in kJ/mol) Given : 0
f 2 6H (C H ,g) 85kJ / mol   ,
0
f 3 8H (C H ,g) 104kJ / mol   , 0
subH (C,s) 718kJ / mol,  B.E. (H-H) = 436 kJ/mol,
a) 414, 345 b) 345, 414 c) 287, 405.5 d) None of these
55 Consider the following data : 0
f 2 4H (N H ,l) 50kJ / mol  0
f 3H (NH ,g) 46kJ / mol  
B.E. (N-H) = 393 kJ/mol and B.E. (H-H) = 436 kJ/mol, vap 2 4H(N H ,l) 18kJ / mol, 
The N-N bond energy in N2
H4
is :
a) 226 kJ/mol b) 154 kJ/mol c) 190 kJ/mol d) None of these
56 If enthalpy of hydrogenation of C6
H6(l)
into C6
H12(l)
is -205 kJ and resonance energy of C6
H6(l)
is
–152 kJ/mol then enthalpy of hydrogenation of is
Assume  Hvap
of C6
H6(l)
, C6
H10(l)
C6
H12(l)
all are equal :
a) – 535.5 kJ/mol b) – 238 kJ/mol c) – 357 kJ/mol d) – 119 kJ/mol
PASSAGE - IV
The thermodynamic property that measures the extent of molecular disorder is called entropy. The
direction of a spontaneous process for which the energy is constant is always the one that increases
the molecular disorder. Entropy change of phase transformation can be calculated using Trouton’s
formula
H
S
T
 
  
 
. In the reversible adiabatic process, however, S will be zero. The rise in
termperature in isobaric and isochoric conditions is found to increase the randomness or entropy of
the system.
S = 2.303C log (T1
/T2
) C = Cp
or Cv
57 The entropy change in an adiabatic process is :
a) zero b) always positive
c) always negative d) sometimes positive and sometimes negative
58 If, water in an insulated vessel at –100
C, suddenly freezes, the entropy change of the system will be
a) +10 J K–1
mol–1
b) –10 J K–1
mol–1
c) zero d) equal to that of surroundings
59. The melting point of a solid is 300 K and its latent heat of fusion is 600 cal mol–1
. The entropy
change for the fusion of 1 mole of the solid (in cal K–1
) at the same temperature would be :
a) 200 b) 2 c) 0.2 d) 20

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PASSAGE -V
G is a thermodynamic property the decrease in which value is the measure of useful work done
At constant temperature and pressure :
Gsystem
< 0 (spontaneous), Gsystem
= 0(equilibrium) Gsystem
> 0 (non - spnotaneous)
Free energy is related to the equilibrium constant, as : G0
= 2.303RT log10
Kc
60 If both H and S are negative, the reaction will be spontaneous :
a) at high temperature b) at low temperature
c) at all temperature d) at absolute zero
61 A reaction has positive values of H and S From this you can deduce that the reaction :
a) must be spontaneous at any temperature b) cannot be spontaneous at any temperature
c) will be spontaneous only at low temperature d) will be spontaneous only at high temperature
62 For a reaction to be spontaneous at all tempeatures :
a) G - ve, H+ ve and S+ ve b) G+ ve, H - ve and S+ ve
c) G - ve, H- ve and S- ve d) G = ve, H- ve and S+ v
Passage - VI
Standard Gibb’s energy of reaction  1G 
at a certain temperature can be computed as
1 1 rG H T S       and the change in the value of rH 
and rS 
for a reaction with temperature
can be computed as follows :  2 1r T r T r P 2 1H H C T T       
2 1
2
r T r T r P
1
T
S S C In
T
 
      
 
  
r r rG H T. S       and by r eqG RT In K  
Consider the following reaction :      2 3Co g 2H g CH OH g 
Given :  f 3H CH OH,g 
= –201 kJ/mol;  f H CO,g 114 kJ/ mol  
 3S CH OH,g 240 J / K mol; 
  1 1
2S H ,g 29 JK mol 

 S CO,g 198 J mol K; 
 p,m 2C H 28.8 J / mol K 
 p,mC CO 29.4 J / mol K 
;  p,m 3C CH OH 44 J / mol K 
and ln
320
300
 
 
 
= 0.06, all data at 300 K
63. rS 
at 300 K for the reaction is :
a) 152 63. J/K mole b) 181.6 J/K mole c) - 16 J/K mole d) None of these
64. rS 
at 320 K is
a)155.18 J/mol-K b) 150.02 J/mol-k c) 172 J/mol-K d) None of these

9. THERMODYNAMICS CHEMISTRY
www.science360.net suresh gdvm
65. rH 
at 320 K is
a) –288.86 kJ/mol b) –289.1 kJ/mol c) –87.86 kJ/mol d) None of these
EXERCISE - III
(Match the following questions)
66 Column-I Column-II
A) C (s, graphite) + O2
(g)  CO2
(g) p) combustionH 
B) C (s, grahpite)  C(g) q) formationH 
C)      2 2
1
CO g O g CO g
2
  r) atomizationH 
D)      4CH g C g 4H g  s) sublimationH 
67 Column-I (Process) Column-II (Entropy Change)
A) Reversible isothermal compression of ideal gas p) systemS 0 
B) Isothermal free expansion (Pext
= 0) of an ideal gas q) systemS 0 
C) Reversible adiabatic expansion of an ideal gas r) systemS 0 
D) Reversible ideal gas expansion s) Information insufficient
68 Column-I Column-II
A) Reversible adiabatic compression p) systemS 0 
B) Reversible vaporization of liquid q) systemS 0 
C)    22N g N g r) surroundingS 0 
D)      3 2MgCO s MgO s CO g

  s) surroundingS 0 
69 Column-I Column-II
a)  system T,P
G 0  p) Process is in equilibrium
b) system surrounding 0S S    q) Process is non spontaneous
c) system surrounding 0S S    r) Process is spontaneous
d)  system T,P
G 0  s) System is unable to do useful work
70 Column-I [ Sign H and S] Column-II
A) – & – p) Spontaneous only at low temperature
B) – & + q) Spontaneous only at high temperature
C) + & + r) Spontaneous at all temperature
D) + & – s) Non-Spontaneous at all temperature