NEET AIPMT Chemistry Chapter Wise Solutions – Thermodynamics

NEET AIPMT Chemistry Chapter Wise Solutions – Thermodynamics

NEET AIPMT Chemistry Chapter Wise SolutionsPhysicsBiology

1.For a given reaction, ΔH = 35.5 kJ mol^-1 and ΔS = 83.6 J K^-1 mol^-1 . The reaction is spontaneous at (Assume that ΔH and ΔS do not vary with temperature.) (NEET 2017)
(a) T > 425 K
(b) all temperatures
(c) T> 298 K
(d) T<425 K

2.A gas is allowed to expand in a well insulated container against a constant external pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of 4.50 L. The change in internal energy ΔU of the gas in joules will be (NEET 2017)
(a) -500 J
(b) -505 J
(c) +505 J
(d) 1136.25 J

3.For a sample of perfect gas when its pressure is changed isothermally from p_i to p_f the entropy change is given by  (NEET II 2016)

4.The correct thermodynamic conditions for the spontaneous reaction at all temperatures is (NEET-I 2016)
(a) ΔH < 0 and ΔS > 0
(b) ΔH < 0 and ΔS < 0
(c) ΔH < 0 and ΔS = 0
(d) ΔH > 0 and ΔS < 0

5.Consider the following liquid-vapour equilibrium. (NEET-I 2016)

6.The heat of combustion of carbon to C0₂ is -393.5 kJ/mol. The heat released upon  formation of 35.2 g of C0₂ from carbon and oxygen gas is (2015)
(a)+315 kJ
(b) – 630 kJ
(c) – 3.15 kJ
(d) – 315 kJ

7. Which of the following statements is correct i for the spontaneous adsorption of a gas? (2014)
(a) ΔS is negative and, therefore ΔH should be highly positive.
(b) ΔS is negative and therefore, ΔH should be highly negative.
(c) ΔS is positive and therefore, ΔH should be negative.
(d) ΔS is positive and therefore, ΔH should also be highly positive.

8. For the reaction, X₂0_4(l) —> 2X0_2(g)
ΔU = 2.1 kcal, ΔS = 20 cal K^-1 at 300 K Hence, ΔG is (2014)
(a) 2.7 kcal
(b) – 2.7 kcal
(c) 9.3 kcal
(d) – 9.3 kcal

9. A reaction having equal energies of activation | for forward and reverse reactions has (NEET 2013)
(a) ΔH = 0
(b)ΔH = ΔG=ΔS=0
(c) ΔS = 0
(d) ΔG = 0

10. When 5 litres of a gas mixture of methane and propane is perfectly combusted at 0°C and 1 atmosphere, 16 litres of oxygen at the same temperature and pressure is consumed. The amount of heat released from this combustion in kJ (ΔH_comb (CH₄) = 890 kJ mol^-1, ΔH_comb (C₃H₈) = 2220 kJ mol^-1) is (Karnataka NEET 2013)
(a) 38
(b) 317
(c) 477
(d) 32

11.Three thermochemical equations are given below 
(i) C(graphite) + 0_2(g) —>CO_2(g) ;ΔH° = x kJ moL^-1
(ii) C(graphite)+ ½ 0_2(g) —> CO_(g) ;ΔH° = y kJ moL^-1
(iii) CO(g) + ½ 0_2(g) —>CO_2(g) ; ΔH°=z kJ moL^-1
Based on the above equations, find out which of the relationship given below is correct, (Karnataka NEET 2013)
(a) z = x + y
(b) x = y + z
(c) y = 2z – x
(d) x = y – z

12. In which of the following reactions, standard reaction entropy change (ΔS°) is positive and standard Gibb’s energy change (ΔG°) decreases sharply with increasing temperature? (2012)
(a) C(graphite) + ½ 0_2(g) —>CO(g)
(b) CO(g) + ½ 0_2(g) —> C0_2(g)
(c) Mg_(s)+ ½ 0_2(g)—> MgO_(s)
(d) 1/2 C(graphite) + ½ 0_2(g)—> ½ CO_2(g)

13. The enthalpy of fusion of water is 1.43 5 kcal/mol. The molar entropy change for the melting of ice at 0°C is (2012)
(a) 10.52 cal/(mol K)
(b) 21.04 cal/(mol K)
(c) 5.260 cal/(mol K)
(d) 0.526 cal/(mol K)

14. Standard enthalpy of vaporisation Δ_vapH° for water at 100°C is 40.66 kJ mol^-1. The internal energy of vaporisation of water at 100°C (in kJ mol^-1) is (2012)
(a) +37.56
(b) -43.76
(c) +43.76
(d) +40.66
(Assume water vapour to behave like an ideal gas)

15. If the enthalpy change for the transition of liquid water to steam is 30 kJ mol^-1 at 27°C, the entropy change for the process would be (2011)
(a) 10 J mol^-1 K^-1
(b) 1.0 J mol^-1 K^-1
(c) 0.1 J mol^-1 K^-1
(d) 100 J mol^-1 K^-1

16. Enthalpy change for the reaction, 4H_(g) —> 2H_2(g) is —869.6 kJ The dissociation energy of H – H bond is (2011)
(a) – 434.8 kJ
(b) – 869.6 kJ
(c) + 434.8 kJ
(d) + 217.4 kJ

17. Which of the following is correct option for free expansion of an ideal gas under adiabatic . condition? (2011)
(a) q = 0, ΔT + 0, w = 0
(b) q ≠ 0, ΔT = 0, w = 0
(c) q = 0, ΔT = 0, w = 0
(d) q = 0, ΔT<0, w≠0

18.Consider the following processes: (Mains 2011)
ΔH (kJ/mol) 
1/2A—>B           +150
3B —>2C + D      -125
E + A —> 2D      +350
For B + D —> E + 2C, AH will be
(a) 525 kJ/mol
(b) -175 kJ/mol
(c) -325 kJ/mol
(d) 325 kJ/mol

19. For an endothermic reaction, energy of activation is E_a and enthalpy of reaction is ΔH (both of these in kJ/mol). Minimum value of E_a will be (2010)
(a) less than ΔH
(b) equal to ΔH
(c) more than ΔH
(d) equal to zero

20. Standard entropies of X₂, Y₂ and XY₃ are 60, 40 and 50 J K^-1 mol^-1 respectively. For the reaction 1/2X₂+ 3/2Y₂= XY₃, ΔH =-30 kJ, to be at equilibrium, the temperature should be (2010)
(a) 750 K
(b) 1000K
(c) 1250 K
(d) 500 K

21.Match List I (Equations) with List II (Type of processes) and select the correct option. (Mains 2010)

(a) A – (i), B – (ii), C – (iii), D – (iv)
(b) A – (iii), B – (iv), C – (ii), D – (i)
(c) A – (iv), B – (i), C – (ii), D – (iii)
(d) A – (ii), B – (i), C – (iv), D – (iii)

22.Three moles of an ideal gas expanded spontaneously into vacuum. The work done will be (Mains 2010)
(a) infinite
(b) 3 Joules
(c) 9 Joules
(d) zero

23. For vaporization of water at 1 atmospheric pressure, the values of ΔH and ΔS are 40.63 kJ mol^-1 and 108.8 J K^-1 mol^-1, respectively. The temperature when Gibb’s energy change ( ΔG) for this transformation will be zero, is (Mains 2010)
(a) 273.4 K
(b) 393.4 K
(c) 373.4 K
(d) 293.4 K

24.The following two reactions are known
Fe₂O_3(s) + 3CO_(g)—> 2Fe_(s)+ 3C0_{2(g) ;}
ΔH= -26.8 kJ 
FeO_(s) + CO—> Fe+ C0_{2(g) ;}
ΔH=-16.5 kJ
The value of AH for the following reaction
Fe₂O_3(s) + CO_(g)—-> 2FeO_(s) + C0_2(g) is (Mains 2010)
(a) + 10.3 kJ
(c) – 10.3 kJ
(b) – 43.3 kJ
(d) + 6.2 kJ

25. The values of ΔH and ΔS for the reaction,C(graphite) + C0_2(g) —> 2CO_(g) are 170 kJ and 170 J K^-1, respectively. This reaction will be spontaneous at (2009)
(a) 910 K
(b) 1110K
(c) 510 K
(d) 710 K

26. From the following bond energies: (2009)

(a) – 243.6 kJ mol^-1
(c) 553.0 kJ mol^-1
(b) – 120.0 kJ mol^-1
(d) 1523.6 kJ mol^-1

27. Bond dissociation enthalpy of H₂, Cl₂ and HCl are 434, 242 and 431 kJ mol^-1 respectively. Enthalpy of formation of HCl is (2008)
(a) -93 kJ mol^-1
(b) 245 kJ mol^-1
(c) 93 kJ mol^-1
(d) -245 kJ mol^-1

28. For the gas phase reaction,
PCl_5(g) =PCl _3(g)+ Cl_2(g)
which of the following conditions are correct? (2008)
(a) ΔH < 0 and ΔS < 0
(b) ΔH > 0 and ΔS < 0
(c) ΔH = 0 and ΔS < 0
(d) ΔH > 0 and ΔS > 0

29. Which of the following are not state functions?  (2008)
(I) q + w
(II) q
(III) w
(IV) H – TS
(a) (I), (II) and (III)
(b) (II) and (III)
(c) (I) and (IV)
(d) (II), (III) and (IV)

30. Consider the following reactions:

Enthalpy of formation of H₂O_(l) is (2007)
(a) +X₃ kJ mol^-1
(b) -X₄ kJ mol^-1
(c) +X₁ kJ mol^-1
(d) -X₂ kJ mol^-1

31. Given that bond energies of H – H and Cl – Cl are 430 kJ mol^-1 and 240 kJ mol^-1 respectively and ΔHf for HCl is -90 kJ mol^-1, bond enthalpy of HCl is (2007)
(a) 380 kJ mol^-1
(b) 425 kJ mol^-1
(c) 245 kJ mol^-1
(d) 290 kJ mol^-1

32. Identify the correct statement for change of Gibb’s energy for a system (ΔG system) at constant temperature and pressure. (2006)
(a) If ΔG system < 0, the process is not spontaneous.
(b) If ΔG system > 0, the process is spontaneous.
(c) If ΔG system = 0, the system has attained equilibrium.
(d) If ΔG system, = 0, the system is still moving in a particular direction.

33. Assume each reaction is carried out in an open container. For which reaction will ΔH = ΔE ?(2006)

34. The enthalpy and entropy change for the reaction:
Br_2(l) + Cl_2(g) —>2BrCl_(g)
are 30 kJ mol^-1 and 105 J K^-1 mol^-1 respectively. The temperature at which the reaction will be in equilibrium is (2006)
(a) 300 K
(b) 285.7 K
(c) 273 K
d) 450 K

35. The enthalpy of hydrogenation of cyclohexene is -119.5 kJ mol^-1. If resonance energy of benzene is -150.4 kJ mol^-1, its enthalpy of hydrogenation would be (2006)
(a) – 358.5 kJ mol^-1
(b) – 508.9 kJ mol^-1
(c) – 208.1 kJ mol^-1
(d) – 269.9 kJ mol^-1

36. Which of the following pairs of a chemical reaction is certain to result in a spontaneous reaction? (2005)
(a) Exothermic and increasing disorder
(b) Exothermic and decreasing disorder
(c) Endothermic and increasing disorder
(d) Endothermic and decreasing disorder

37. A reaction occurs spontaneously if (2005)
(a) TΔS < ΔH and both ΔH and ΔS are +ve
(b) TΔS > ΔH and ΔH is +ve and ΔS is -ve
(c) TΔS > ΔH and both ΔH and ΔS are +ve
(d) TΔS = ΔH and both ΔH and ΔS are +ve

38. The absolute enthalpy of neutralisation of the reaction:. (2005)
MgO_(s) + 2HCl_(aq) —> MgCl_2(aq) + H₂0_(l) will be
(a) -57.33 kJ mol ^-1
(b) greater than -57.33 kJ mol^-1
(c) less than -57.33 kJ mol^-1
(d) 57.33 kJ mol^–1

39. If the bond energies of H-H, Br-Br, and H-Br are 433,192 and 364 kJ mol^-1 respectively, the ΔH° for the reaction H_2(g) + Br_2(g) —> 2HBr_(g) is (2004)
(a) -261 kJ
(b) +103 kJ
(c) +261 kJ
(d) -103 kJ

40. Standard enthalpy and standard entropy changes for the oxidation of ammonia at 298 K are -382.64 kJ mol^-1 and -145.6 kJ mol^-1, respectively. Standard Gibb’s energy change for the same reaction at 298 K is (2004)
(a) – 221.1 kJ mol^-1
(b) – 339.3 kJ mol^-1
(c) – 439.3 kJ mol^-1
(d) – 523.2 kJ mol^-1

41. Considering entropy (S) as a thermodynamic parameter, the criterion for the spontaneity of any process is (2004)
(a) ΔS System+ ΔS surroundings > 0
(b) ΔS System — ΔS surroundings > 0
(c) ΔS system > 0 only
(d) ΔS surroundings > 0 only.

42. The work done during the expansion of a gas from a volume of 4 dm³ to 6 dm³ against a constant external pressure of 3 atm is (1 L atm = 101.32 J) (2004)
(a) – 6 J
(b) – 608 J
(c) + 304 J
(d) – 304 J

43. For the reaction,
C₂H_8(g) + 50_2(g) —> 3C0_2(g) + 4H₂0_(l) 
at constant temperature,ΔH – ΔE is (2003)
(a) +RT
(b) -3RT
(c) +3RT
(d)-RT

44. The densities of graphite and diamond at 298 K are 2.25 and 3.31 g Cm^-3, respectively. If the standard free energy difference (ΔG°) is equal to 1895 J mol^-1, the pressure at which graphite will be transformed into diamond at 298 K is (2003)
(a) 9.92 x 10⁸ Pa
(b) 9.92 x 10⁷ Pa
(c) 9.92 x 10⁶ Pa
(d) 9.92 x 10⁵ Pa

45. What is the entropy change (in J K^-1 mol^-1) when one mole of ice is converted into water at 0°C? (The enthalpy change for the conversion of ice to liquid water is 6.0 kJ mol^-1 at 0°C.) (2003)
(a) 20.13
(b) 2.013
(c) 2.198
(d) 21.98

46. Formation of a solution from two components can be considered as
(i) Pure solvent —> separated solvent molecules, ΔH1
(ii) Pure solute —> separated solute molecules, ΔH2
(iii) Separated solvent and solute molecules —> solution, ΔH3
Solution so formed will be ideal if (2003)
(a)ΔH soln = ΔH1+ ΔH2 + ΔH3
(b)ΔH soln = ΔH1 + ΔH2 – ΔH3
(c) ΔH soln = ΔH1- ΔH2 – ΔH3
(d) ΔH soln = ΔH3- ΔH1 – ΔH2

47. For which one of the following equations is ΔHºreact equal to ΔH°f for the product? (2003)
(a) N_2(g) + O_3(g) —>N₂O_3(g)
(b) CH_4(g) + 2Cl_2(g) —> CH₂Cl_2(l)+ 2HCl_(g)
(c) Xe_(g) + 2F_2(g) —> XeF_4(g)
(d) 2CO_(g) + 0_2(g) —> 2C0_2(g)

48. The molar heat capacity of water at constant pressure, C , is 75 J K^-1 mol^-1. When 1.0 kJ of heat is supplied to 100 g of water which is free to expand, the increase in temperature of water is (2003)
(a) 1.2 K
(b) 2.4 K
(c) 4.8 K
(d) 6.6K

49. Unit of entropy is (2002)
(a) J K^-1 mol^-1
(b) J mol^-1
(c) J^-1 K^-1 mol^-1
(d) J K mol^-1

50. In a closed insulated container a liquid is stirred with a paddle to increase the temperature which of the following is true? (2002)
(a) ΔE=W≠0, q = 0
(b) ΔE = W = q ≠0
(c) ΔE = 0, W= q ≠ 0
(d) W=0, ΔE=q≠0.

51. Heat of combustion ΔH for C_(s), H_2(g) and CH_4(g) are -94, -68 and -213 kcal/mol, then ΔH for C_(s)+ 2H_2(g)-> CH_4(g) is (2002)
(a) -17 kcal
(b) -111 kcal
(c) -170 kcal
(d) -85 kcal

52. Which reaction is not feasible? (2002)
(a) 2KI + Br₂ —> 2KBr + I₂
(b) 2KBr + I₂ –>2KI + Br₂
(c) 2KBr + Cl₂ -> 2KCl + Br₂
(d) 2H₂0 + 2F₂ -> 4HF + O₂

53. 2 mole of ideal gas at 27°C temperature is expanded reversibly from 2 lit. to 20 lit. Find entropy change. (R = 2 cal/mol K) (2002)
(a) 92.1
(b)0
(c) 4
(d) 9.2

54. Change in enthalpy for reaction,
2H₂0_2(l) —> 2H₂0_(l) + 0_2(g)
if heat of formation of H₂0_2(l) and H₂0_(l) are -188 and -286 kJ/mol respectively, is (2001)
(a) -196 kJ/mol
(b) +196kJ/mol
(c) +948 kJ/mol
(d) -948 kJ/moie

55. When 1 mol of gas is heated at constant volume temperature is raised from 298 to 308 K. Heat supplied to the gas is 500 J. Then which statement is correct? (2001)
(a) q = w = 500 J,ΔE = 0
(b) q = ΔE = 500 J, w = 0
(c) q = w = 500 J, ΔE = 0
(d) ΔE = 0, q = w = -500 J

56. Enthalpy of CH₄+ 1/2 0₂ —> CH₃OH is negative. If enthalpy of combustion of CH₄ and CH₃OH are x and y respectively. Then which relation is correct? (2001)
(a) x> y
(b) x < y
(c) x=y
(d) x³y

57. Pb0₂ —> PbO; ΔG₂₉₈ <0
Sn0₂ —> SnO; AG₂₉₈> 0
Most probable oxidation state of Pb and Sn will be (2011)
(a) Pb⁴⁺, Sn⁴⁺
(b) Pb⁴⁺, Sn²⁺
(c) Pb²⁺, Sn²⁺
(d) Pb²⁺, Sn⁴⁺

58. Cell reaction is spontaneous when (2000)
(a) ΔG° is negative
(b) ΔG° is positive
(c) ΔE°red  is positive
(d) ΔE°red is negative.

59. 2Zn + 0₂ —> 2ZnO; ΔG° = -616 J
2Zn + S₂ —>+ 2ZnS; ΔG° = -293 J
S₂ + 20₂ —>+ 2S0₂; ΔG° = -408
ΔG° for the following reaction 2ZnS + 30₂ —> 2ZnO + 2S0₂ is (2000)
(a) -731 J
(b) -1317 J
(c) -501 J
(d) +731 J

60. At 27°C latent heat of fusion of a compound is 2930 J/mol. Entropy change is (2000)
(a) 9.77 J/mol-K
(b) 10.77 J/mol-K
(c) 9.07 J/mol-K
(d) 0.977 J/mol-K

61. For the reaction,
C₂H₅OH_(l) + 30_2(g) —> 2C0_2(g)+ 3H₂0_(l) which one is true (2000)
(a) ΔH = ΔE – RT
(b) ΔH = ΔE + RT
(c) ΔH = ΔE + 2RT
(d) ΔH = ΔE- 2RT

62. In an endothermic reaction, the value of ΔH is (1999)
(a) negative
(b) positive
(c) zero
(d) constant.

63. In the reaction: S + 3/2 0₂ —> S0₃ + 2x kcal and S0₂ + 1/2 0₂ —> S0₃ + y kcal, the heat of formation of S0₂ is (1999)
(a) (2x+y)
(b) (x – y)
(c)(x + y)
(d) (2x-y)

64. Identify the cojrect statement tegarding entropy. (1998)
(a) At absolute zero of temperature, the entropy of all crystalline substances is taken to be zero.
(b) At absolute zero of temperature, the entropy of a perfectly crystalline substance is +ve.
(c) At absolute zero of temperature, entropy of a perfectly crystalline substance is taken to be zero.
(d) At 0°C, the entropy of a perfectly crystalline substance is taken to be zero.

65. One mole of an ideal gas at 300 K is expanded isothermally from an initial volume of 1 litre to 10 litres. The ΔE for this process is (1998)
(R = 2 cal mol^-1K^-1)
(a) 1381.1 cal
(b) zero
(c) 163.7 cal
(d) 9Latm

66. Given that C + O₂ —> C0₂, ΔH° = – x kJ 2CO + 0₂ —> 2C0₂, ΔH° = -y kJThe enthalpy of formation of carbon monoxide will be y-2x (1997)
(a) y-2x/2
(b) 2x-y
(c) y – 2x
(d)2x-y/2

67. Which of the following is the correct equation? (1996)
(a) ΔU = ΔW+ ΔQ
(b) ΔU=ΔQ-W
(c) ΔW= ΔU + ΔQ
(d) None of these

68. If enthalpies of formation for C₂H_4(g), C0_2(g) and H₂0_(l) at 25°C and 1 atm pressure are 52, – 394 and – 286 kJ/mol respectively, then enthalpy of combustion of C₂H₄will be (1995)
(a) +141.2 kJ/mol
(b) +1412 kJ/mol
(c) – 141.2 kJ/mol
(d) – 1412 kJ/mol

69. A chemical reaction is catalyzed by a catalyst X. Hence X (1995)
(a) reduces enthalpy of the reaction
(b) does not affect equilibrium constant of reaction
(c) decreases rate constant of the reaction
(d) increases activation energy of the reaction.

70. Standard state Gibb’s free energy change for isomerization reaction cis-2-pentene = trans- 2-pentene is -3.67 kJ/mol at 400 K. If more trans-2-pentene is added to the reaction vessel, then (1995)
(a) equilibrium remains unaffected
(b) equilibrium is shifted in the forward direction
(c) more cis-2-pentene is formed
(d) additional trans-2-pentene is formed.

71. For a reaction to occur spontaneously (1995)
(a) ΔH must be negative
(b) ΔS must be negative
(c) (ΔH – TΔS) must be negative
(d) (ΔH + TΔS) must be negative.

72. During isothermal expansion of an ideal gas, its (1994, 91)
(a) internal energy increases
(b) enthalpy decreases
(c) enthalpy remains unaffected
(d) enthalpy reduces to zero.

73. Following reaction occurring in an automobile 2C₈H_18(g)+ 250_2(g)—» 16C0_2(g) + 18H₂0(g) The sign of ΔH, ΔS and ΔG would be (1994)
(a) -,+, +
(b) +, +, –
(c)+,-,+
(d) -, +, –

74. For the reaction N₂ + 3H₂ = 2NH₃, ΔH = ? (1991)
(a) ΔE + 2RT
(b) ΔE – 2RT
(c) ΔH = RT
(d) ΔE-RT

75. If ΔH is the change in enthalpy and ΔE, the change in internal energy accompanying a gaseous reaction, then (1990)
(a) ΔH is always greater than ΔE
(b) ΔH < ΔE only if the number of moles of the products is greater than the number of moles of the reactants
(c) ΔH is always less than ΔE
(d) ΔH < ΔE only if the number of moles of products is less than the number of moles of the reactants.

Answer Key

Explanations