Unit 2chemical Thermodynamics

7/27/2019 Unit 2chemical Thermodynamics

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Unit 2

CHEMICAL THERMODYNAMICS [Q1 TO Q86]

1) The enthalpy change for the reaction

H2O (s) H2O (l)is called

A) Enthalpy of formation

B) Enthalpy of fusionC) Enthalpy of vaporization

D) Enthalpy of transition

2) H is related to E asA) H-E =pV

B) H = E-pVC) H + E = p V

D) V p E

H

3) The entropy of the universeA) tends towards a maximum

B) tends towards a minimumC) tends to be zero

D) remains constant

4) Which of the following conditions is not favorable for the feasibility of a process?A) H = -Ve, T S = - Ve and T S< H

B) H = +Ve, TS = + Ve and T S>HC) H = -Ve, TS = + Ve and H>T S

D) H = +Ve, TS = + Ve and H>T S

5) In which of the following cases, the reaction is spontaneous at all temperatures?A) H>0, S>0

B) H<0, S>0C) H<0, S<0

D) H>0, S<0

6) For a system in equilibrium, G = 0 under conditions of constantA) Temperature and pressure

B) Temperature and volumeC) Pressure and volume

D) Energy and volume

7) For an endothermic reaction. S is positive. The reaction is:



A) feasible when T S> HB) feasible when H>T S

C) feasible at all temperaturesD) not feasible at all

8) When potassium chloride is dissolved in water A) entropy increasesB) entropy decreases

C) entropy increases and then decreasesD) free energy increases

9) All the naturally occurring processes proceed spontaneously in a direction which

leads toA) decrease of entropy

B) increase of enthalpyC) increase of free energy

D) decrease of free energy

10) For a reversible process at equilibrium, the change in entropy may be expressed asA) S = Tqrev

B) S =T

revq

C) S = -T

H

D) S = G

11) Free energy, G may be defined asA) G = E– TS

B) G = E+ TSC) G = H – TS

D) G = E+ H – TS

12) For a spontaneous reaction, G should beA) positive

B) negativeC) equal to zero

D) may be positive or negative

13) When a solid changes into liquid, the entropyA) increases

B) remains the sameC) decreases

D) becomes zero

14) Entropy is a measure of A) disorder

B) internal energy



C) efficiencyD) useful work done by the system

15) If q is the heat added to the system, w is the work done by the system and E is the

change in internal energy, then according to first law of thermodynamics

A)

E = q + wB) E = q-wC) E = q + pV

D) E = q + H

16) When a solid is converted directly into gaseous state, the process is calledsublimation. The entropy change during the process is:

A) zeroB) negative

C) positiveD) may be negative or zero

17) Which of the following processes is accompanied by decreases in entropy?

A) Evaporation of water B) sublimation of dry ice

C) melting of iceD) condensing steam

18) Free energy is related to enthalpy and entropy changes as

A) G = H - T SB) G = T S - H

C) G =T

S H

D) G = H + T S

19) A spontaneous changes is one in which the system suffers

A) increase in internal energyB) lowering of entropy

C) lowering of free energyD) no energy change

20) For which of the following reactions, S is not positive?

A) )(2)(2 g I s I

B) CuO( s) + H2( g )

Cu( s) + H2O(i)C) 2O3( g ) 3O2( g )

D) CH4( g ) + 2O2( g )CO2( g ) + 2H2O( g ).

21) For an equilibrium state,

A) H > 0B) G > 0

C) H = T S



D) H > T S

22) For which of the following reactions, H is equal to E

A) N2(g) + 3H2(g) 2NH3(g)

B) PCI5(g)

PCI3(g) + Cl2(g)C) 2H2S(g) + 3O2(g) 2H2O (i) + 2SO2(g)

D) C(s) + O2(g) CO2(g).

23) For the reaction

PCI5(g) PCI3(g) + Cl2(g)

A) H = EB) H > E

C) H < ED) none of the above

24) The standard free energy changes ( G

0

is related to equilibrium constant (K) asA) G = -2.303 RT in K

B) G = 2.303 RT in K

C) G = -2.303 RT log K

D) G = RT log K.

25) The units of entropy are :A) J mol

-1

B) JK -1

mol-1

C) J g

-1

D)

JK mol-1

26) For a chemical reaction at constant P, H is equal toA) Zero

B) EC) q / T

D) E+ pV

27) Under which of the following conditions is the relation H = E + PV valid for aclosed system?

A) constant pressure

B) constant temperatureC) constant temperature and pressureD) constant temperature, pressure and composition

28) The enthalpy change for the process:

C(s)C(g)

Corresponds to enthalpy of A) fusion



B) sublimationC) combustion

D) vaporization

29) In electrochemical cell, if E is the EMF of the cell involving n mole of electrons, then

G 0 is :A) G = nFE

B) G = -nFE

C) E = nF G

D) G = E

nF

30) For a spontaneous endothermic reaction

A) G > 0

B) G = 0

C) H < 0

D) S >T

H

31) For the reversible vapourisation of water at 373 K and 1 atmospheric pressure, ∆G is

equal toA) ∆H

B) ∆S C) Zero

D) ∆H/T

32) For a chemical reaction at constant P and V, H is equal toA) E

B) ZeroC) E+P V

D) p/T

33) ( E- H) for the formation of NH3 from N2 and H2 isA) -2 RT

B) 2 RTC) RT

D) ½ RT

34) The sign of G for the process of melting of ice at 260 K is:A) G = 0

B) G < 0C) G > 0

D) G 0



35) The enthalpies of formation of N2O and NO at 298 K are 82 and 90 Kj

mol-1

. The enthalpy of the reaction: N20 (g) + ½ O2 (g) 2NO (g) is

A) -8 k JB) 98 k JC) -74 k J

D) 8 k J

36) A system absorbs 10 kJ of heat at constant volume and its temperature rises from 27C to 37 C. The values of E is :

A) 100 k JB) 10 k J

C) 0D) 1 kJ

37) The enthalpies of combustion of carbon and carbon monoxide are -395.5 and -283.0

kJ mol-1 respectively. The enthalpy of formation of carbon monoxide is:A) -676.5 kJ

B) 110.5 kJC) -110.5 kJ

D) 676.5 kJ

38) The standard enthalpies of formation of HCl(g), H(g) and Cl(g) are -92.2, 217.7 and121.4 kJ mol

-1respectively. The bond dissociation energy of HCl is

A) +431.3 kJB) 236.9 kJ

C) -431.3kJD) 339.1 k

39) For the reaction at 300 K

A(g) + B (g) C(g),E= -3.0 Kcal S =-10.0 cal/K(R = 2 cal mol-1

K -1

) G is

A) -600 calB) -3600 cal

C) 2400 calD) 3000 cal.

40) The enthalpy of vaporization of a substance is 8400 J mol-1

and its boiling point is -

1730C the entropy change for the vaporization isA) 84 J mol-1 K

B) 21 J mol-1

K C) 49 J mol

-1K

D) 12 J mol-1 K



41) If equilibrium constant K is 103, the G for the reaction at 300 K is (assume R = 8

JK -1 mol-1

A) -16.582 kJ

B) 16.582 kJC) 165.82 kJD) -1143.2 kJ

42) The enthalpy of vaporization of a compound AB at its boiling point (1270C) is 6.4 kJ

mol-1

. Its entropy of vaporization is:A) 2.56 kJ mol

-1

B) 16 J mol-1

C) 16 × 10-3 J mol-1

D) 1.6 × 103

kJ mol-1

43) The equilibrium constant for a reaction is 10.∆

G

0

will be (R=8 JK

-1

mol

-1

, T = 300K)

A) -5527 kJ mol-1

B) -5.527 kJ mol-1 C) -55.27 kJ mol

-1

D) +5.527 kJ mol-1

44) H(vap) for water is 40.7 kJ mol-1

. The entropy of vaporization of water is:

A) -40.7 kJ mol-1

K -1

B) 407 J mol

-1K

-1

C) 109 J mol-1

K -1

D)

722 J mol

-1

45) The following data is known about the melting a compound AB. H=9.2 kJ mol-1.

S =0.008 kJ K -1

mol-1

. Its melting point isA) 736 K

B) 1050 K C) 1150 K

D) 11500C

46) For a reaction, X + Y Z There is no entropy change, Enthalpy change for the

reaction is 100J mol-1. G is

A) -100 J mol

-1

B) 100 J mol-1

C) 0

D) Infinite



47) H for the reaction SO2(g)+1/2 O2(g) SO3(g) If the enthalpy of formation of

SO3(g) is -395.4 then the enthalpy of formation of SO2(g) is:

A) -297.1 kJ

B) 493.7 kJC) -493.7 kJD) 297.1 kJ

48) The difference between heats of reaction at constant pressure and constant volume for

the reaction

2C6H6(l ) +15 02(g) 12CO2(g)+6H2O(l ) at 250C is

A) -7.43 kJ

B) +3.72 kJC) -3.72 kJ

D) 7.43 kJ

49) Heat of formation of H2O(g) at 250C is -243 kJ. E for the reaction at 25

0C is:

A) +241.8 kJ

B) -241.8 kJC) -243 kJ

D) 243 kJ

50) Which of the following is true for the reaction? H20(l ) H2O(g) at 1000C and 1 atm

pressureA) S = 0

B) H = T S

C)

H =

ED) H = 0

51) The enthalpy of vaporization of water is 186.5 kJ mol-1

. The entropy of itsvaporization will be

A) 2.0 KJ-1 B) 200 JK

-1

C) 0.5 JK -1

D) 1.5 JK -1

52) For the reaction 2NH3 (g) N2(g) + 3H2(g)

A) q p = (qv)

2

B) q p = qv – 2RT

C) q p = qv + 2 RTD) q p = 2qv –R.



53) The heat changes for a hypothetical reaction at constant pressure

A2B(s) + 2C(g) 2AC(g) + ½ B2(l ) is +102.6 kJ. The heat change for the above

reaction at constant volume is:

A) -102.6 kJB) 102.6 kJC) Less than 102.6 kJ

D) Greater than 102.6 kJ

54) The free energy change for the formation of magnesium oxide from its element at25

0C is -570.5 kJ mol

-1. For reaction

2Mg(s)+O2(g) 2MgO(s)

A) G = -1141.0 kJB) G

0= -1141.0 kJ

C) G0

= 1141.0 kJ

D)

G

0

= 0

55) For reaction

H2(g)+1/2 O2(g) H2O(l )

H = -68 kcalThe heat change for the decomposition of 7.2 g of water is

A) 13.6 KcalB) 27.2 Kcal

C) 54.4 KcalD) -34 kcal

56) Which of the following statements / relationships is not correct?A) In an exothermic reaction, enthalpy of products is less than that of reactantsB) A reaction for which H0 < 0 and S0>0 is spontaneous at all temperatures

C) H is less than E for the reaction : C(s)+1/2 O2(g) CO(g)

D) vapH = subH- fusH.

57) For the process : CO2(s)CO2(g)

A) Both H and S are +ve

B) H is –ve S is +veC) H is +ve S is -ve

D) Both H and S are –ve

58) If H is the change in enthalpy and E is the change in internal energyaccompanying a gaseous reaction then

A) H is always greater than EB) H > E only if the number of moles of the reactants is less than the number

of moles of productsC) H is always less than E



D) H < E only if the number of moles of products is less than the number of moles of reactants

59) The molar heat of vaporization for water is 9.72 kcal mol-1. The amount of heat

change when 45 g of water condense is :

A) 437.4 kcalB) 24.3 kcalC) 243 kcal

D) 3.89 kcal

60) Which of the following properties of a system undergoing change at a constanttemperature and pressure is a measure of the maximum useful work that the system

can do?A) G

B) SC) H

D) P

V

61) For a reaction to be spontaneous at all temperaturesA) G and H should be negative

B) H = G = 0C) G and H should be positive

D) H < G

62) The free energy change G = 0, whenA) the system is at equilibrium

B) catalyst is addedC) reactants are initially mixed thoroughly

D) the reactants are completely consumed

63) At constant T and P which one of the following statements is correct for the reaction?

CO(g)+1/2O2(g)CO2(g)

A) H = EB) H < E

C) H > ED) H is independent of the physical state of the reactant of that compound

64) For the process:C(s)+O2(g) CO2(g), it is found that G at a given temperature is

40.0 kJ mol-1

. At this temperature

A) The system is at equilibriumB) CO2 will be formed spontaneously

C) CO2 will be decompose spontaneouslyD) The process is not possible

65) For the reaction to occur spontaneously

A) S must be negative



B) ( H – TS) must be negativeC) ( H + TS) must be negative

D) H must be negative

66) f H0

of CO2(g), CO(g), N2O(g) and NO2(g)are respectively -393, -110, 81 and 34 (in

kJ mol

-1

) at 27

0

C.

H (in kJ) for the reaction 2NO2(g) + 3CO(g)

N2O(g) +3CO2(g) isA) 836

B) 1460C) -836

D) -1460

67) The enthalpy and entropy of a reaction are -5.0 kJ mol-1

and -20 JK -1

mol-1

respectively and independent of temperature. The highest temperature upto which

reaction is feasible is:A) 250 K

B) 240 K C) 275 K

D) 300 K

68) If H and E are the changes in enthalpy and internal energy when a liquid isconverted into its vapours at temperature T, then

A) H - E = 0B) H-E =22 kJ/mol

C) H-E = RTD) E-H = RT

69) The free energy change for the reaction is zero when

A) the reactants are initially mixedB) catalyst is added

C) the system is at equilibriumD) the reactants are completely consumed

70) The dissociation energy of CH4 and C2H6 are respectively 1508 and 2594 kJ mol-1

respectively. The bond energy of C-C bond isA) 332 kJ mol

-1

B) 316 kJ mol-1

C) 806 kJ mol

-1

D) 320 kJ mol-1

71) The enthalpy change in freezing 1g of water ( H fusion = 6.0 Kj mol-1) will be

A) -6000.0 JB) -333 J

C) 333.33 JD) 60.0 J



72) Change in enthalpy for the reaction:

2H2O2(g) 2H2O(l ) + O2(g)

If heat of formation of H2O2 (l ) and H2O(l ) are -188 kJ mol

-1

and -286 kJmol

-1

respectively isA) -196 kJmol

-1

B) +196 kJ mol-1 C) +948 kJ mol

-1

D) -948 kJ mol-1

73) For which one of the following equations is r H0

equal to ƒH0

for the product?

A) N2(g)+O3(g) N2O3(g)

B) CH4(g)+2Cl2(g) CH2Cl2(g)+2HCl(g)

C) Xe(g)+2F2(g) XeF4(g)

D) 2CO(g)+O2(g) 2CO2(g)

74) For the reaction

C3H8(g)+5O2(g) 3CO2 (g)+4H2O(l ) at constant temperature, H-E is

A) +RT

B) -3RTC) +3RTD) –RT

75) The bond energies of C-C ,C = C, H-H and C-H linkages are 350, 600, 400 and 410

kJ per mol respectively. The heat of hydrogenation of ethylene is

A) -170 kJ mol

-1

B) -260 kJ mol-1

C) -400 kJ mol-1

D) -450 kJ mol-1

76) Which of the following reaction defines ƒ H0?

A) C(diamond)+O2 (g) CO2(g)

B) 2

1H2(g) +

2

1F2(g) HF(g)

C) N2(g) + 3H2(g) 2NH3(g)

D) CO(g) +

2

1O2 (g) CO2(g)

77) If the bond energies og H-H, Br-Br and H-Br are 433, 192 and 364 kJ mol-1

respectively, the ∆H0

for the reaction:

H2(g) + Br 2(g) 2HBr(g) is

A) +103 kJ

B) 261 kJC) -103 kJ



D) -261 kJ

78) Considering entropy (S) as a thermodynamic parameter, the criterion for thespontaneity of any process is

A) S system - S surroundings > 0

B)

S system > 0 onlyC) S surroundings > 0 onlyD) S system + S surroundings > 0

79) The mathematical expression for all types of pressure volume type of work is given as

A) W = V ΔP

B) W = -V ΔP C) W = -PΔV

D) W = PΔV

80) Internal energy is a state function because

A) It depends on the path of reactionB) It depends on the measurable macroscopic properties

C) It is independent of the path of the reactionD) Its absolute value cannot be determined

81) The second law of thermodynamics is explained by the reaction

A) CaCo3 (S) CaO + CO2 (g)

B) H2 O(l )H2O(g)

C) N2(g) + 3H2 (g) 2NH3

D) NaOH + HCl NaCl + H2O

82) The positive sign of free energy change denotes that the process isA) Non spontaneous

B) SpontaneousC) Equilibrium

D) Cyclic

83) Criterian for Sponteinty of a process for an endothermic reaction which of thefollowing is always >0

A) ΔS B) ΔH

C) ΔT

D) ΔG

84) A process is spontaneous at all temperatures if

A) Δ H<0 and Δ S<0 B) ΔH=0 and ΔS<0 C) ΔH>0 and ΔS<0

D) ΔH<0 and S>0



85) The change in the number of moles of gaseous butane when it undergoes combustion

at constant volume isA) 2.5

B) –2.5

C) –3.5D) 3.5

86) If a system absorbs reversibly 750 J of heat and performs 330 J of work the increasein the internal energy of the system is

A) 330 JB) 750 J

C) 420 JD) 1080 J



Answer Key Of Unit 2

CHEMICAL THERMODYNAMICS

Ques. No. Answer 1 B

2 A

3 A

4 D

5 B

6 A

7 A

8 A

9 D

10 B

11 C

12 B

13 A

14 A

15 B

16 C

17 D

18 A

19 C

20 B

21 C

22 D

23 B24 C

25 B

26 D

27 C

28 B

29 B30 D

31 C

32 A

33 C

34 C

35 B

36 B

37 C

38 A

39 A

40 A

41 A

42 B

43 B

44 C

45 C

46 B

47 A

48 A

49 B

50 B

51 C

52 C53 B

54 A

55 B

56 C

57 A

58 D59 B

60 A

61 A

62 A

63 B

64 C

65 B

66 C

67 A

68 C

69 C

70 A

71 C

72 A

73 C

74 B

75 A

76 B

77 C

78 D

79 C

80 D

81 D82 A

83 B

84 D

85 C

86 C

Unit 2chemical Thermodynamics

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