Thermodynamics exercise.pdf

PRE-MEDICAL PHYSICAL CHEMISTRY ENTHUSIAST | LEADER | ACHIEVER EXERCISE Chemical Thermodynamics & Energetics ENGLISH MEDIUM  ® Chemistry : Chemical Thermodynamics...

PRE-MEDICAL PHYSICAL CHEMISTRY ENTHUSIAST | LEADER | ACHIEVER EXERCISE Chemical Thermodynamics & Energetics ENGLISH MEDIUM  ® Chemistry : Chemical Thermodynamics and Energetics Pre-Medical EXERCISE-I (Conceptual Questions) Build Up Your Understanding INTRODUCTION 8. Which one is dependent on initial and final state? 1. Thermodynamics is concerned with :- (1) Heat supplied at constant pressure (2) Heat supplied at constant volume (1) Total energy of a system (3) Enthalpy (2) Energy changes in a system (4) All of the above (3) Rate of a chemical change TH0008 (4) Mass changes in nuclear reactions 9. Out of boiling point (I), entropy (II), pH (III) and TH0001 emf of a cell (IV), intensive properties are : 2. A well stoppered thermos flask contains some ice (1) I, III, IV (2) I, II (3) I, II, III (4) All of these cubes. This is an example of :– TH0009 (1) Closed system 10. The work done by a weightless piston in causing (2) Open system ® an expansion ∆V (at constant temperature), (3) Isolated system when the opposing pressure P is variable, is (4) Non-thermodynamic system given by : TH0002 (1) W = – ∫ PdV (2) W = 0 3. Identify the intensive quantities from the following - (3) W = – P∆V (4) None (1) Enthalpy and temperature TH0010 (2) Volume and temperature 11. The work done by 100 calorie of heat in (3) Enthalpy and volume isothermal expansion of ideal gas is :- (4) Temperature and refractive index (1) 418.4 J (2) 4.184 J TH0003 (3) 41.84 J (4) None TH0011 4. Which of the following is an extensive property 12. Temperature and volume are not :- (1) Mass (2) Enthalpy (1) Extensive properties (3) Energy (4) All of these (2) Intensive properties TH0004 (3) Intensive and extensive properties respectively 5. For an adiabatic process which of the following (4) Extensive and intensive properties respectively relations is correct TH0012 (1) ∆E = 0 (2) P∆V = 0 13. q = –w is not true for :- (3) q = 0 (4) q = + W (1) Isothermal process (2) Adiabatic process (3) Cyclic process (4) 1 and 3 both TH0005 TH0013 6. In which of the following process work is 14. The temperature of an ideal gas increase in an - independent of path : (1) Adiabatic compression (1) Isothermal (2) Isochoric (2) Adiabatic expansion (3) Adiabatic (4) Isobaric (3) Isothermal expansion TH0006 (4) Isothermal compression TH0014 7. When a gas is compressed adiabatically and 15. Which statement is true for reversible process :– reversibly, the final temperature is- (1) It takes place in single step (1) Higher than the initial temperature (2) Driving force is much greater than opposing (2) Lower than the initial temperature force (3) The same as initial temperature (3) Work obtained is minimum (4) Dependent upon the rate of compression (4) None TH0007 TH0016 240  Chemistry : Chemical Thermodynamics and Energetics ® Pre-Medical FIRST LAW OF THERMODYNAMICS (∆E = q + W) 23. For a gaseous reaction, 16. Both q & w are_ _ _ _ _ function :- A(g) + 3B(g) → 3C(g) + 3D(g) ∆ E is 17 kCal at 27 C assuming R = 2 Cal K 0 –1 (1) State (2) State, Path mol , the value of ∆H for the above reaction is: –1 (3) Path, State (4) Path (1) 15.8 Kcal (2) 18.2 Kcal TH0017 (3) 20.0 Kcal (4) 16.4 Kcal 17. If work done by the system is 300 joule when TH0025 100 cal. heat is supplied to it. The change in 24. Which of the following statements is correct for internal energy during the process is :- the reaction ; 2SO2(g) + O2(g) → 2SO3(g) at (1) – 200 Joule (2) 400 Joule constant temperature and pressure (3) 720 Joule (4) 120 Joule (1) ∆H = ∆E (2) ∆H < ∆E TH0018 (3) ∆H > ∆E (4) None of the above 18 A system has internal energy equal to E1, 450 J of TH0026 heat is taken out of it and 600 J of work is done 25. For the reaction Ag2O(s) → 2Ag(s) + ½ O2(g), ® on it. The final energy of the system will be - which one of the following is true : (1) (E1 + 150) (2) (E1 + 1050) (1) ∆H = ∆E (2) ∆H = ½ ∆E (3) (E1 – 150) (4) None of these (3) ∆H < ∆E (4) ∆H > ∆E TH0019 TH0027 19. The work done by a system is 8J when 40J heat 26. A mixture of 2 moles of carbon monoxide and is supplied to it. The change in internal energy of one mole of oxygen in a closed vessel is ignited the system during the process : to get carbon dioxide. If ∆H is the enthalpy (1) 32 J (2) 40 J change and ∆E is the change in internal energy, (3) 48 J (4) –32 J then :– TH0020 (1) ∆H > ∆E (2) ∆H < ∆E (3) ∆H = ∆E (4) Not definite ENTHALPY [∆H=∆E + P∆V/∆H= ∆E + ∆ng RT] TH0028 20. Internal energy change during a reversible 27. For the gaseous reaction involving the complete isothermal expansion of an ideal gas is :- combustion of isobutane - (1) Always negative (1) ∆Η = ∆E (2) ∆Η > ∆E (2) Always positive (3) ∆Η = ∆E = 0 (4) ∆Η < ∆E (3) Zero TH0029 (4) May be positive or negative 28. For the reversible isothermal expansion of one TH0022 mole of an ideal gas at 300 K, from a volume of 21. Under which of the following conditions is the 10 dm to 20 dm , ∆H is - 3 3 relation, ∆H = ∆E + P∆V valid for a system :– (1) 1.73 kJ (2) –1.73 kJ (1) Constant pressure (3) 3.46 kJ (4) Zero (2) Constant temperature TH0030 (3) Constant temperature and pressure 29. For CaCO3(s) → CaO(s) + CO2(g) at 977°C, (4) Constant temperature, pressure and composition ∆H = 174 KJ/mol ; then ∆E is :- TH0023 (1) 160 kJ (2) 163.6 kJ 22. The difference between heats of reaction at (3) 186.4 kJ (4) 180 kJ constant pressure and constant volume for the TH0031 reaction 30. Heat of reaction for , CO(g) + ½ O2(g) → CO2(g) 2C6H6(l) + 15O2(g) → 12CO2(g) + 6H2O(l) at at constant V is –67.71 K cal at 17°C. The heat 0 25 C in KJ is of reaction at constant P at 17°C is :- (1) + 7.43 (2) +3.72 (1) –68.0 kCal (2) + 68.0 kCal (3) – 7.43 (4) – 3.72 (3) – 67.42 kCal (4) None TH0024 TH0032 241  ® Chemistry : Chemical Thermodynamics and Energetics Pre-Medical 31. The enthalpy of vaporisation of water at 1000C 38. For which of the following reactions ∆H is less is 40.63 kJ mol. The value ∆E for this process –1 than ∆E :– would be:- (1) C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O() –1 –1 (1) 37.53 kJ mol (2) 39.08 kJ mol (2) 2SO2(g) + O2(g) → 2SO3(g) –1 (3) 42.19 kJ mol (4) 43.73 kJ mol–1 (3) N2O4(g) → 2NO2(g) TH0034 (4) N2(g) + O2(g) → 2NO(g) 32. For the system S(s) + O2(g) → SO2(g) :– TH0041 (1) ∆H = ∆E (2) ∆H > ∆E 39. For a reaction 2X(s) + 2Y(s) → 2C() + D(g) (3) ∆E > ∆H (4) ∆H = 0 –1 The qp at 27°C is – 28 kCal mol. TH0035 The qV is _______ kCal mol–1 :– 1 (1) – 27.4 (2) + 27.4 (3) – 28.6 (4) 28.6 33. For the reaction CO (g) + O2 (g) → CO2 (g) 2 TH0042 ® Which one of these statement is correct at WORK DONE IN DIFFERENT PROCESS constant T and P ? 40. The work (in ergs) for a reversible expansion of (1) ∆H = ∆E one mole of an ideal gas from a volume of (2) ∆H < ∆E 10 litres to 20 litres at 250C is : (3) ∆H > ∆E (1) –2.303 × 8.314 × 107 × 298 log2 (4) ∆H is Independent of physical state of reactants (2) –2.303 × 0.0821 × 298 log2 TH0036 (3) –2.303 × 0.0821 × 298 log 0.5 34. Which is true for the combustion of sucrose (4) –2.303 × 2 × 298 log2 TH0043 (C12H22O11) at 25°C :- 41. Two moles of an ideal gas expand spontaneously (1) ∆H > ∆E (2) ∆H < ∆E into vacuum. The work is :– (3) ∆H = ∆E (4) None (1) Zero (2) 2 J (3) 4 J (4) 8 J TH0037 TH0045 35. For which change ∆H ≠ ∆E :- 42. One mole of a gas occupying 3dm3 expands  (1) H2(g) + I2(g)  2HI(g) against a constant external pressure of 1 atm to (2) HCl () + NaOH () → NaCl (s) + H2O () a volume of 13 L. Find work is :– (1) – 10 atm dm3 (2) – 20 atm dm3 (3) C(s) + O2(g) → CO2(g) (3) – 39 atm dm3 (4) – 48 atm dm3 (4) N2(g) + 3H2(g) → 2NH3(g) TH0046 TH0038 ENTROPY/SECOND LAW OF THERMODYNAMICS 36. The heat of combustion of ethanol determined in 43. For which reaction from the following, ∆S will be a bomb calorimeter is – 670.48 kCal mole–1 at maximum ? 27°C. What is ∆H at 27°C for the reaction :– (1) Ca(s) + ½ O2(g) → CaO(s) (1) – 335.24 kCal (2) – 671.08 kCal (2) CaCO3(s) → CaO(s) + CO2(g) (3) C(s) + O2(g) → CO2 (g) (3) – 670.48 kCal (4) + 670.48 kCal (4) N2(g) + O2(g) → 2NO(g) TH0039 TD0047 37. The difference in ∆H and ∆E for the combustion 44. An adiabatic reversible process is one in which :- of methane at 25°C would be :– (1) Temperature of the system does not change (1) Zero (2) 2 × 298 × – 2 Cal (2) The system is not closed to heat transfer (3) 2 × 298 × – 3 Cal (4) 2 × 25 × – 3 Cal (3) There is no entropy change (4) None of these TH0040 TD0048 242  Chemistry : Chemical Thermodynamics and Energetics ® Pre-Medical 45. Entropy means 54. If 900J/g of heat is exchanged at boiling point of (1) Disorderness (2) Randomness water, then what is increase in entropy? (3) Orderness (4) both 1 & 2 (1) 43.4 JK–1mole–1 –1 (2) 87.2 JK mole –1 TD0049 –1 (3) 900 JK mole –1 (4) Zero 46. ∆S for the reaction; TD0059 MgCO3(s) → MgO(s) + CO2(g) will be : 55. 5 mole of an ideal gas expand reversibly from a (1) 0 (2) –ve (3) +ve (4) ∞ volume of 8 dm3 to 80dm3 at a temperature of TD0050 0 27 C. The change in entropy is :– 47. Change in entropy is negative for (1) 41.57 JK–1 (2) – 95.73 JK–1 (1) Br2 () → Br2(g) (3) 95.73 JK–1 (4) – 41.57 JK –1 (2) C(s) + H2O(g) → CO(g) + H2(g) TD0060 (3) N2(g, 10 atm) → N2 (g, 1 atm) 56. In a spontaneous irreversible process the total (4) Fe(at 400 K) → Fe(at 300 K) entropy of the system and surroundings TD0051 ® (1) Remains constant (2) Increases 48. In which reaction ∆S is positive :- (3) Decreases (4) Zero (1) H2O () → H2O (s) TD0061 (2) 3O2 (g) → 2O3 (g) 57. The total entropy change for a system & its (3) H2O () → H2O (g) surroundings increases if the process is : (1) Reversible (2) Spontaneous (4) N2(g) + 3H2(g) → 2NH3 (g) TD0052 (3) Exothermic (4) Endothermic TD0062 49. When the egg is hard boiled, there is- (1) Increase in disorder 58. Calculate the entropy of Br2(g) in the reaction (2) Decrease in disorder H2(g) + Br2(g) → 2HBr(g), ∆S° =20.1JK–1 given, (3) No change in disorder entropy of H2 and HBr is 130.6 and (4) ∆G is negative 198.5 J mol–1 K–1 :- TD0053 (1) 246.3 JK–1 (2) 123.15 JK–1 50. 0 If S for H2, Cl2 and HCl are 0.13, 0.22 and (3) 24.63 JK–1 (4) 20 kJK–1 0.19 kJ K–1 mol–1 respectively. The total change TD0063 in standard entropy for the reaction 59. In which of the following case entropy decreases– H2 + Cl2 → 2HCl is : –1 –1 –1 –1 (1) Solid changing to liquid (1) 30 JK mol (2) 40 JK mol –1 –1 (2) Expansion of a gas (3) 60 JK mol (4) 20 JK mol–1 –1 (3) Crystals dissolve TD0054 51. Which has the least entropy : (4) Polymerisation (1) Graphite (2) Diamond TD0065 (3) N2(g) (4) N2O(g) 60. Which of the following quantity is not zero for TD0055 element in standard state :– 52. When two gases are mixed the entropy :– (1) Enthalpy of formation (1) Remains constant (2) Decreases (2) Entropy (3) Increases (4) Becomes zero (3) Free energy of formation TD0056 (4) All of these 53. The enthalpy of vaporisation of per mole of TD0066 ethanol (B.pt. = 79.5 C and ∆S = 109.8 JK 0 –1 –1 61. Entropy of an adiabatic reversible process is:- mol ) is :– –1 (1) Positive (2) Zero (1) 27.35 kJ mol (2) 32.19 kJ mol–1 –1 (3) Negative (4) Constant (3) 38.70 kJ mol (4) 42.37 kJ mol–1 TD0058 TD0067 243  ® Chemistry : Chemical Thermodynamics and Energetics Pre-Medical GIBBS FREE ENERGY 69. For the precipitation of AgCl by Ag ions and + 62. A gas is allowed to expand under reversible HCl adiabatic conditions then :- (1) ∆ H = 0 (2) ∆ G = 0 (1) ∆U = 0 (2) ∆T = 0 (3) ∆ G = –ve (4) ∆ H = ∆ G (3) ∆S = 0 (4) None of these TD0077 TD0068 70. What is the sign of ∆G for the process of ice melting at 1 atm, 283 K is ? 63. 0 For a reaction at 25 C enthalpy change (∆H) and (1) ∆G > 0 (2) ∆G = 0 entropy change (∆S) are –11.7 × 103 Jmol–1 and (3) ∆G < 0 (4) None of these –105 J mol–1 K–1 respectively. The reaction is : TD0078 (1) Spontaneous (2) Non spontaneous 71. A reaction A + B → C + D + q is found to (3) At equilibrium (4) Can't say anything have a positive entropy change, the reaction will TD0069 be - 64. If ∆ H > 0 and ∆ S > 0, the reaction proceeds (1) Possible at high temperature ® spontaneously when :- (2) Possible only at low temperature (1) ∆H > 0 (2) ∆H < T∆S (3) Not possible at any temperature (3) ∆H = T∆S (4) None (4) Possible at any temperature TD0071 TD0080 72. Equilibrium constant of a reaction is related to : 65. The temperature at which the reaction (1) Standard free energy change ∆G0 Ag2O(s) → 2Ag(s) + ½ O2(g) (2) Free energy change ∆G is at equilibrium is........; (3) Entropy change Given ∆H = 30.5 kJ mol–1 (4) None ∆S = 0.066 kJK mol : –1 –1 and TD0081 (1) 462.12 K (2) 362.12 K 73. The Vant Hoff equation is : (3) 262.12 K (4) 562.12 K (1) ∆G° = RT loge KP (2) –∆G° = RT logeKP TD0072 (3) ∆ G° = RT nKP 2 (4) None 66. Which of the following is true for the reaction TD0082 H2O()  H2O(g) at 1000C and 1 atmosphere 74. If ∆ G > 0 for a reaction then : 0 (1) ∆S = 0 (2) ∆H = 0 (1) KP > 1 (3) ∆H = ∆E (4) ∆H = T∆S (2) KP < 1 TD0074 (3) The products predominate in the equilibrium 67. For the reaction A(s) → B(s) + C(g) the value of mixture (4) None ∆H = 30.56 kJ mol and ∆S=66 JK mol. –1 –1 –1 TD0083 The temperature at which the free energy 75. If the equilibrium constant for a reaction is 10, change for the reaction will be zero is :– then the value of ∆G will be 0 (1) 373 K (2) 413 K –1 –1 (R = 8JK mol , T = 300 K) (3) 463 K (4) 493 K –1 (1) + 5.527 kJ mol (2) – 5.527 kJ mol–1 TD0075 –1 –1 (3) +55.27 kJ mol (4) – 55.27 kJ mol 68. For hypothetical reversible reaction TD0084 ½ A2(g) + 3 B2 (g) → AB3(g); ∆H = –20 kJ if 2 76. The process of evaporation of a liquid is standard entropies of A2, B2 and AB3 are 60, 40 accompanied by : and 50 JK–1 mole–1 respectively. The above (1) Increase in enthalpy reaction will be in equilibrium at :– (2) Decrease in free energy (1) 400 K (2) 500 K (3) Increase in entropy (3) 250 K (4) 200 K (4) All TD0076 TD0085 244  Chemistry : Chemical Thermodynamics and Energetics ® Pre-Medical 77. For the process, CO2(s) → CO2(g) : 83. Which one of the following is not applicable for a (1) Both ∆H and ∆S are +ve thermochemical equation : (2) ∆H is negative and ∆S is +ve (1) It tells about physical state of reactants and (3) ∆H is +ve and ∆S is –ve products (4) Both ∆H and ∆S are –ve (2) It tells whether the reaction is spontaneous TD0086 (3) It tells whether the reaction is exothermic or endothermic 78. Which of the following provide exceptions to (4) It tells about the allotropic form (if any) of the third law of thermodynamics reactants (1) CO (2) ice TC0092 (3) CO2 (4) All the above 84. The correct thermochemical equation is : TD0087 (1) C + O2 → CO2 ; ∆ H = – 94 kCal 79. The Gibbs free energy change of a reaction at (2) C + O2 → CO2 ; ∆ H = + 94.0 kCal 27°C is –26 kCal and its entropy change is (3) C(s) + O2(g) → CO2(g) ; ∆ H = –94 kCal – 60 Cal K–1. ∆H for the reaction is :– (4) C(s) + O2(g) → CO2(g); ∆ H = +94 kCal (1) – 44 kCal (2) – 18 kCal ® (3) 34 kCal (4) – 24 kCal TC0093 TD0088 85. The enthalpy changes of formation of the gaseous 80. Which of the following reaction is expected never oxide of nitrogen (N2O and NO) are positive to be spontaneous :– because of : (1) The high bond energy of the nitrogen molecule (1) 2O3(g) → 3O2(g) ∆H=– Ve, ∆S = +Ve (2) The high electron affinity of oxygen atoms (2) Mg(s) + H2(g) → MgH2 ∆H=– Ve, ∆S = – Ve (3) The high electron affinity of nitrogen atoms (3) Br2(I) → Br2(g) ∆H=+ Ve, ∆S = + Ve 2– (4) The tendency of oxygen to form O (4) 2Ag(s) + 3N2(g) → 2AgN3 ∆H=+Ve, ∆S=– Ve TC0094 TD0089 86. ∆H for transition of carbon from diamond form to THERMOCHEMICAL REACTION graphite form is – 453.5 Cal. This suggests that : 81. The formation of water from H2(g) and O2(g) is (1) Graphite is chemically different from diamond (2) Graphite is as stable as diamond an exothermic process because : (3) Graphite is more stable than diamond (1) The chemical energy of H2(g) and O2(g) is (4) Diamond is more stable than graphite more than that of water TC0095 (2) The chemical energy of H2(g) and O2(g) is less 87. Which of the following values of heat of formation than that of water indicates that the product is least stable (3) The temperature of H2(g) and O2(g) is higher (1) – 94 kCal (2) – 231.6 kCal than that of water (3) + 21.4 kCal (4) + 64.8 kCal (4) The temperature of H2(g) and O2(g) is lower TC0096 than that of water 88. Heat of formation, ∆Hof of an explosive compound TC0090 like NCl3 is – 82. Which plot represents for an exothermic reaction: (1) Positive (2) Negative R (3) Zero (4) Positive or negative (1) H (2) H R P TC0097 P Progress in Progress in 89. According to the following reaction reaction reaction C(s) + 1/2 O2(g) → CO(g), ∆H = - 26.4 kCal P (1) CO is an endothermic compound (3) H (4) H R P (2) CO is an exothermic compound R Progress in Progress in (3) The reaction is endothermic reaction reaction (4) None of the above TC0091 TC0098 245  ® Chemistry : Chemical Thermodynamics and Energetics Pre-Medical 90. Which of the following represents an exothermic ENTHALPY OF FORMATION reaction:- 96. Since the enthalpy of formation of the elements (1) N2(g) + O2(g) → 2NO(g), ∆H = 180.5 kJ in their standard states is taken to be zero. (2) H2O(g) + C(s) → CO(g) + H2(g), ∆E = 131.2kJ The heat of formation (∆Hf ) of compounds : (3) 2HgO(s) + 180.4 KJ → 2Hg() + O2(g) (1) Is always negative (4) 2Zn(s) + O2(g) → 2ZnO(s), ∆E = - 693.8 kJ (2) Is always positive TC0099 (3) Is zero (4) May be positive or negative 91. Consider the reaction 3O2 → 2O3 ; ∆H = + Ve, TC0107 from the reaction, we can say that :– (1) Ozone is more stable then oxygen 97. Reaction H2(g) + I2(s) → 2HI; ∆H = 12.40 kCal. (2) Ozone is less stable then oxygen and ozone According to this, heat of formation of HI will be – decomposes forming oxygen readily (1) 12.40 kCal (2) – 12.40 kCal (3) Oxygen is less stable than ozone and oxygen (3) – 6.20 kCal (4) 6.20 kCal ® decomposes forming ozone readily TC0108 (4) None of the above 98. Enthalpy of a compound is equal to its :- TC0101 (When it is formed from reference state of 92. From the reaction P(White) → P(Red) ; constituent elements) ∆H = –18.4 kJ, it follows that :- (1) Red P is readily formed from white P (1) Heat of combustion (2) White P is readily formed from red P (2) Heat of formation (3) White P can not be converted to red p (3) Heat of reaction (4) White P can be converted into red P and red (4) Heat of solution P is more stable TC0110 TC0102 99. Which of the following equations respresents FACTORS AFFECTING ENTHALPY standard heat of formation of CH4 ? OF REACTION (1) C(diamond) + 2H2 (g) → CH4 (g) 93. In Kirchoff's equation which factor affects the (2) C(graphite) + 2H2 (g) → CH4 (g) heat of reaction : (3) C(diamond) + 4H (g) → CH4 (g) (1) Pressure (2) Temperature (4) C(graphite) + 4H(g) → CH4 (g) (3) Volume (4) Atomicity TC0111 TC0103 94. The enthalpy of a reaction at 273 K is –3.57 kJ. 100. The enthalpy of formation of ammonia is what will be the enthalpy of reaction at 373 K –46.0 kJ mol–1. The enthalpy change for the if ∆Cp = zero :– reaction 2NH3(g) → N2(g) + 3H2(g) is : (1) – 3.57 kJ (2) Zero (1) 46.0 kJ mol–1 (2) 92.0 kJ mol –1 373 (3) – 23.0 kJ mol–1 (4) – 92.0 kJ mol –1 (3) – 3.57 × kJ (4) – 375 kJ 273 TC0112 TC0105 101. Given enthalpy of formation of CO2(g) and 95. For the reactions, CaO(s) are – 94.0 kJ and – 152 kJ respectively (i) H2(g) + Cl2(g) → 2HCl(g) + xkJ and the enthalpy of the reaction : (ii) H2(g) + Cl2(g) → 2HCl() + ykJ CaCO3(s) → CaO(s) + CO2(g) is 42 kJ. Which one of the following statement is correct : The enthalpy of formation of CaCO3(s) is (1) x > y (2) x < y (1) – 42 KJ (2) – 202 KJ (3) x = y (4) More data required (3) +202 KJ (4) – 288KJ TC0106 TC0113 246  Chemistry : Chemical Thermodynamics and Energetics ® Pre-Medical 102. Given that standard enthalpy of formation of CH4, 109. The standard enthalpy of formation of NO2(g) and –1 C2H4 and C3H8 are –17.9, 12.5, –24.8 kCal mol. N2O4(g) are 8.0 and 2.0 kCal mol–1 respectively The ∆H for CH4 + C2H4 → C3H8 is : the heat of dimerization of NO2 in kCal is (1) – 55.2 kCal (2) – 30.2 kCal (1) 10.0 (2) –6.0 (3) –12.0 (4) –14.0 (3) 55.2 kCal (4) – 19.4 kCal TC0122 TC0114 110. M is a metal that forms an oxide M2O 103. The standard molar enthalpy of formation of 1 1 M2O → M + O2 ∆H = 120 kCal ethane, CO2 and water are respectively –21.1, – 2 4 94.1 and – 68.3 kCal. The standard molar heat When a sample of metal M reacts with one mole of combustion of ethane will be of oxygen what will be the ∆H in that case (1) –372 kCal (2) –162 kCal (1) 240 kCal (2) – 240 kCal (3) – 240 kCal (4) –183.5 kCal (3) 480 kCal (4) – 480 kCal TC0115 TC0123 ® 104. The ∆H o for CO2(g), CO(g) and H2O(g) are f ENTHALPY OF COMBUSTION –393.5, –110.5 and –241.8 kJ mol–1respectively 111. According to equation, the standard enthalpy change (in kJ) for the C6H6() + 15/2 O2(g) → 6CO2(g) + 3H2O(); ∆H reaction CO2(g)+H2 (g)→ CO(g)+ H2O(g) is - –1 (1) 524.1 (2) 41.2 (3) –262.5 (4) –41.2 = – 3264.4 kJ mol the energy evolved when TC0117 7.8 g benzene is burnt in air will be - 105. The enthalpies of combustion of carbon and (1) 163.22 kJ (2) 32.64 kJ carbon monoxide are –393.5 kJ and –283 kJ, (3) 3.264 kJ (4) 326.4 kJ respectively the enthalpy of formation of carbon TC0124 monoxide is : 112. Enthalpy of combustion of CH4,C2H6, C2H4 and (1) –676.5 kJ (2) –110.5 kJ C2H2 gases are –212.8, –373.0, –337.0 and (3) 110.5 kJ (4) 676.5 kJ –310.5 kCal respectively at the same temperature. TC0118 The best fuel among these gases is : 106. The standard enthalpy of formation of CS2() will (1) CH4 (2) C2H6 (3) C2H4 (4) C2H2 be; given that the standard enthalpy of TC0125 combustion of carbon (s), sulphur(s) and CS2() 113. Given standard enthalpy of formation of are –393.3, –293.72 and –1108.76 kJ mol–1 –1 CO ( –110 kJ mol ) and CO2(–394 kJ mol ). –1 respectively is –1 The heat of combustion when one mole of (1) –128.02 kJ mole (2) +12.802 kJ mol–1 graphite burns is (3) +128.02 kJ mol–1 (4) –12.802 kJ mol–1 (1) – 110 kJ (2) – 284 kJ TC0119 107. The enthalpy of combustion of CH4 (g) , C(s) and (3) – 394 kJ (4) – 504 kJ H2 (g) at 25 °C are –212.4 K Cal, –94.0 K Cal TC0126 and –68.4 K Cal respectively, the enthalpy of 114. The enthalpy of formation for C2H4(g), CO2(g) formation of CH4 will be - and H2O() at 250C and 1 atm. pressure are 52, (1) +54.4 K Cal (2) –18.4 K Cal – 394 and – 286 kJ mole–1 respectively. The (3) –375.2 K Cal (4) +212.8 K Cal enthalpy of combustion of C2H4 will be:- TC0120 (1) + 1412 kJ mole–1 108. Standard enthalpy of formation is zero for. (2) –1412 kJ mole–1 (1) Cdiamond (2) Br(g) (3) + 142.2 kJ mole–1 (3) Cgraphite (4) O3(g) (4) –141.2 kJ mole–1 TC0121 TC0127 247  ® Chemistry : Chemical Thermodynamics and Energetics Pre-Medical 115. The combustion of one mole of benzene takes 121. In the combustion of 0.4 g. of CH4, 0.25 kCal. place at 298 K and 1 atm. After combustion, of heat is liberated. The heat of combustion of CO2(g) and H2O(l) are produced and 3267.0 kJ CH4 is of heat is liberated. Calculate the standard (1) – 20 kCal (2) – 10 kCal enthalpy of formation, ∆ f H of benzene. (3) – 2.5 kCal (4) – 5 kCal Standard enthalpies of formation of CO2(g) and –1 –1 TC0137 H2O(l) are –393.5 kJ mol and –285.83 kJ mol respectively. 122. If C6H12O6(s) + 9O2(g) → 6CO2(g) + 6H2O(g); (1) 48.51 kJ mol –1 (2) –48.51 kJ mol –1 ∆H= – 680 kCal The weight of CO2(g) produced (3) –97.02 kJ mol–1 (4) 97.02 kJ mol–1 when 170 kCal of heat is evolved in the TC0128 combustion of glucose is:- 116. The heat evolved during the combustion of 112 (1) 265 g (2) 66 g litre of water gas at STP (mixture of equal (3) 11 g (4) 64 g volume of H2 and CO) is : Given ® TC0138 H2(g) + ½ O2(g) → H2O (g) ; ∆H = –241.8 kJ 123. Which of the following equations corresponds to CO(g) + ½ O2(g) → CO2(g) ; ∆H = –283 kJ the enthalpy of combustion at 298 K :- (1) 241.8 kJ (2) 283 kJ (3) 1312 kJ (4) 1586 kJ (1) C2H6(g) + 7/2 O2(g) → 2CO2(g) + 3H2O(g) TC0130 (2) 2C2H6(g) + 7 O2(g) → 4CO2(g) + 6H2O(g) 117. A person requires 2870 kCal of energy to lead (3) C2H6(g) + 7/2 O2(g) → 2CO2(g) + 3H2O() normal daily life. If heat of combustion of cane –1 (4) 2C2H6(g) + 7O2(g) → 4CO2(g) + 6H2O() sugar is –1349 kCalmol , then his daily consumption of sugar is : TC0139 (1) 728 g (2) 0.728 g 124. Heat of formation of CO2 is – 94.0 kCal. What (3) 342 g (4) 0.342 g would be the quantity of heat liberated, when 3 g TC0131 of graphite is burnt in excess of oxygen:- 118. The following are the heats of reactions - –1 (1) 23.5 kCal (2) 2.35 kCal (i) ∆Hof of H2O() = –68.3 kCal mol (3) 94.0 kCal (4) 31.3 kCal –1 (ii) ∆Hocomb. of C2H2 = –337.2 kCal mol TC0140 (iii) ∆H o comb. of C2H4 = –363.7 kCal mol –1 ENTHALPY OF HYDROGENATION Then heat change for the reaction 125. The heat of combustion of C2H4, C2H6 and H2 C2H2 + H2 → C2H4 is - are –1409.5 kJ, –1558.3 kJ and –285.6 kJ. (1) –716.1 kCal (2) + 337.2 kCal (3) –41.8 kCal (4) –579.5 kCal The heat of hydrogenation of ethene is - TC0134 (1) –136.8 kJ (2) –13.68 kJ 119. The heat of combustion of a substance is :- (3) 273.6 kJ (4) 1.368 kJ (1) Always positive TC0149 (2) Always negative (3) Numerically equal to the heat of formation 126. The enthalpy of combustion of cyclohexane, (4) 1 and 3 both cyclohexene and H2 are respectively –3920, TC0135 -1 –3800 and –241 kJ mol. The heat of 120. The value of ∆H for the combustion of C(s) is hydrogenation of cyclohexene is:- –94.4 kCal. The heat of formation of CO2(g) is :- (1) –121 kJ mol–1 (2) 121 kJ mol–1 (1) –49.5 kCal (2) –94.4 kCal –1 (3) –188.0 kCal (4) More data required (3) –242 kJ mol (4) 242 kJ mol–1 TC0136 TC0150 248  Chemistry : Chemical Thermodynamics and Energetics ® Pre-Medical BOND ENTHALPY/BOND DISSOCIATION ENTHALPY 133. Bond dissociation enthalphies of H2(g) and N2(g) –1 –1 127. Bond enthalpy of a molecule : are 436.0 kJ mol and 941.8 kJ mol (1) Is always negative respectively and enthalpy of formation of NH3(g) –1 (2) Is always positive is –46 kJ mol. What is enthalpy of atomization (3) Either positive or negative of NH3(g) ? (4) Depends upon the physical state of the system (1) 390.3 kJ mol –1 (2) 1170.9 kJ mol–1 TC0151 (3) 590 kJ mol –1 (4) 720 kJ mol –1 128. Among the following for which reaction heat of TC0157 reaction represents bond enthalpy of HCl 134. From the reactions : (1) HCl(g) → H (g) + Cl (g) + – C(s) + 2H2(g) → CH4(g) ∆H = – X kcal (2) HCl(g) → ½ H2(g) + ½ Cl2(g) C(g) + 4H(g) → CH4(g), ∆H = – X1 kcal (3) 2HCl(g) → H2(g) + Cl2(g) CH4(g) → CH3(g) + H(g) ∆H = + Y kcal (4) HCl(g) → H(g) + Cl(g) ® Bond enthalpy of C–H bond is – TC0152 129. The bond enthalpies of F2, Cl2, Br2 and I2 are X –1 –1 (1) kCal mol (2) Y kCal mol –1 4 155.4, 243.6, 193.2 and 151.2 kJ mol X1 respectively. The strongest bond is : (3) kCal mol–1 (4) X1 kCal mol–1 4 (1) F – F (2) Cl – Cl TC0158 (3) Br – Br (4) I – I TC0153 135. The enthalpy changes at 298 K in successive 130. Energy required to dissociate 4g of gaseous breaking of O–H bonds of water are hydrogen into free gaseous atoms is 208 kCal at H2O → H(g) + OH(g) ; ∆H = 498 kJ mol–1 0 25 C. The bond enthalpy of H—H bond will be : OH(g) → H(g) + O(g) ; ∆H = 428 kJmol –1 (1) 1.04 kCal (2) 10.4 kCal the bond enthalpy of O–H bond is (3) 104 kCal (4) 1040 kCal (1) 498 kJ mol–1 (2) 428 kJ mol–1 TC0154 (3) 70 kJ mol–1 (4) 463 kJ mol–1 131. Heat evolved in the reaction H2 + Cl2 → 2HCl TC0159 is 182 kJ. Bond enthalpy of H–H and Cl–Cl are 430 and 242 kJ mol–1 respectively. The H–Cl 136. If ∆Hof of ICl(g) , Cl(g) , and I(g) is 17.57, 121.34 bond enthalpy is : and 106.96 J mol–1 respectively. Then bond –1 –1 (1) 245 kJ mol (2) 427 kJ mol dissociation enthalpy of ICl bond is - –1 (3) 336 kJ mol (4) 154 kJ mol–1 (1) 35.15 J mol–1 (2) 106.69 J mol–1 TC0155 (3) 210.73 J mol–1 (4) 420.9 J mol–1 132. The enthalpy change for the reaction TC0160 H2(g) + C2H4(g) → C2H6(g) is............ The bond SOME OTHER ENTHALPY OF REACTIONS enthalpies are in kCal mol–1 H – H = 103, C – H = 99, C – C = 80 & 137. The enthalpy change for the reaction C = C =145 2C(graphite) + 3H2(g) → C2H6 (g) is called –1 (1) –10 kCal mol (1) Enthalpy of formation –1 (2) +10 kCal mol (2) Enthalpy of combustion –1 (3) – 30 kCal mol (3) Enthalpy of hydrogenation (4) +30 kCal mol–1 (4) Enthalpy of vaporisation TC0156 TC0162 249  ® Chemistry : Chemical Thermodynamics and Energetics Pre-Medical 138. Cl2(g) → 2Cl(g), In this process value of ∆H 144. Given that : TK will be - A(s)  → A() ; ∆H = x, TK (1) Positive A()  → A(g) ; ∆H = y (2) Negative Calculate enthalpy of sublimation at 'T'k :- (1) x + y (2) x - y (3) Zero (3) x or y (4) – (x + y) (4) Nothing can be predicted TC0172 TC0163 HESS LAW 139. If H2(g) → 2H(g) ; ∆H = 104 kCal, than 145. The enthalpy change of a reaction does not enthalpy of atomisation of hydrogen is : depend on (1) 52 kCal (2) 104 kCal (1) State of reactants and products (3) 208 kCal (4) None of these (2) Nature of reactants and products ® TC0165 (3) Different intermediate reactions (4) Initial and final enthalpy change of reaction 140. S(rhombic) + O2(g) → SO2(g) ; ∆H = –297.5 kJ TC0173 S(monoclinic) + O2 (g) → SO2 ; ∆ H = –300 kJ 146. From the thermochemical reactions, The data can predict that – C(graphite) + ½ O2 → CO ; ∆H = – 110.5 kJ (1) Rhombic sulphur is yellow in colour CO + ½ O2 → CO2 ; ∆ H = – 283.2 kJ (2) Monoclinic sulphur has metallic lusture. the heat of reaction of C(graphite) + O2 → CO2 is : (3) Monoclinic sulphur is more stable (1) 393.7 kJ (2) – 393.7 kJ (4) ∆ H transition of SR to SM is endothermic (3) – 172.7 kJ (4) + 172.7 kJ TC0166 TC0174 141. The enthalpy of combustion of yellow 147. If H2 + ½O2 → H2O ; ∆ H = – 68.39 kCal phosphorous and red phosphorous are – 9.91 kJ K + H2O → KOH(aq) + ½ H2 ; and –8.78 kJ respectively. The enthalpy of ∆H = – 48.0 kCal transition of yellow phosphorous to red KOH + aq. → KOH (aq) ∆H = – 14.0 kCal phosphorous is the enthalpy of formation of KOH is - (1) –18.69 kJ (2) +1.13 kJ (1) – 68.39 + 48 – 14.0 (3) +18.69 kJ (4) –1.13 kJ (2) – 68.39 – 48.0 +14.0 TC0167 (3) +68.39 – 48.0 + 14.0 142. 2CO(g) + O2(g) → 2CO2(g) + X kJ (4) + 68.39 + 48.0 – 14.0 In the above equation X kJ refers to : TC0175 (1) enthalpy of formation of CO2 148. Given C(s) + O2(g) → CO2(g) + 94.2 kCal (2) enthalpy of vapourisation H2(g) + ½O2(g) → H2O() + 68.3 kCal (3) enthalpy of reaction CH4(g) + 2O2(g) → CO2(g) + 2H2O()+210.8 kCal (4) enthalpy of sublimation The enthalpy of formation of methane in Kcal TC0169 will be 143. ∆H for the reaction, I(g) + I(g) → I2(g) will be:- (1) –45.9 (2) –47.8 (1) Zero (2) – ve (3) + ve (4) ∞ (3) –20.0 (4) –47.3 TC0171 TC0176 250  Chemistry : Chemical Thermodynamics and Energetics ® Pre-Medical 149. If, H2(g) + Cl2(g) → 2HCl(g) ; ∆H = –44 kCal 0 154. The heat of reaction for 2Na(s) + 2HCl(g) → 2NaCl(s) + H2(g); 1 A+ O2 → AO is - 50 kCal and ∆H = – 152 kCal 0 2 Then, Na(s) + 0.5 Cl2(g) → NaCl(s) ; ∆H = ? 0 1 AO + O2 → AO2 is 100 kCal. The heat of (1) 108 kCal (2) 196 kCal 2 (3) – 98 kCal (4) 54 kCal reaction for A + O2 → AO2 is:- TC0178 (1) – 50 kCal (2) + 50 kCal 150. (i) S(s) + 3/2 O2(g) → SO3(g) + 2x kCal (3) 100 kCal (4) 150 kCal (ii) SO2(g) + ½ O2(g) → SO3(g) + y kCal TC0184 Calculate the enthalpy of formation of SO2 : 155. C(s) + O2(g) → CO2(g) + 94.0 kCal (1) (2x + y) (2) –(2x – y) 1 (3) x + y (4) 2x / y CO(g) + O2(g) → CO2(g), ∆H = –67.7 kCal ® 2 TC0179 from the above reactions find how much heat 151. If S + O2 → SO2 ; ∆H = –298.2 kJ -1 (kCal mole ) would be produced in the following SO2 + ½ O2 → SO3 ; ∆H = –98.7 kJ 1 SO3 + H2O → H2SO4 ; ∆H = –130.2 kJ reaction : C(s) + O2(g) → CO(g) 2 H2 + ½ O2 → H2O ; ∆H = –287.3 kJ (1) 20.6 (2) 26.3 Then the enthalpy of formation of H2SO4 at 298 K is - (3) 44.2 (4) 161.6 (1) –814.4 kJ (2) –650.3 kJ TC0185 (3) –320.5 kJ (4) –433.5 kJ 156. The enthalpy of vapourisation of liquid water TC0180 using the data: 152. Given that : 1 H2(g)+ O2(g)→ H2O() ; ∆H = –285.77 kJ mol-1 Zn + ½ O2 → ZnO + 84000 Cal..................1 2 Hg + ½ O2 → HgO + 21700 Cal..................2 1 O2(g) → H2O(g) ; ∆H=–241.84 kJ mol -1 H2(g)+ The enthalpy of reaction (∆H) for, 2 Zn + HgO → ZnO + Hg is :- (1) + 43.93 kJ mol –1 (2) - 43.93 kJ mol–1 (1) 105700 Cal (2) 62300 Cal –1 (3) + 527.61 kJ mol (4) - 527.61 kJ mol–1 (3) –105700 Cal (4) – 62300 Cal TC0187 TC0181 1 153. Given that - 157. H2(g)+ O2(g)→H2O() ; ∆H298K = –68.32kCal. 2 2C(s) + 2O2(g) → 2CO2(g) ∆H = –787 kJ Enthalpy of vapourisation of water at 1 atm and H2(g) + ½O2(g) → H2O() ∆H = –286 kJ 0 25 C is 10.52 kCal. The standard enthalpy of 5 C2H2(g)+ O2(g)→2CO2(g)+H2O()∆H=–1310 kJ formation (in kCal) of 1 mole of water vapour at 2 0 Enthalpy of formation of acetylene is :- 25 C is (1) + 1802 kJ (2) – 1802 kJ (1) 10.52 (2) –78.84 (3) – 800 kJ (4) + 237 kJ (3) +57.80 (4) –57.80 TC0182 TC0188 251  ® Chemistry : Chemical Thermodynamics and Energetics Pre-Medical 158. Which of the following expressions is true:- 1 (1) H0f (CO,g)= ∆ H0f (CO2,g) 2 1 (2) ∆ H0f (CO,g)=∆ H0f (C,graphite) + ∆Hf0(O2,g) 2 1 (3) ∆ H0f (CO,g)=∆ H0f (CO2,g) – ∆ H0f (O2,g) 2 (4) ∆ H0f (CO,g)=∆ H0comb (C,graphite)–∆ H0comb (CO,g) TC0191 Que. EXERCISE-I (Conceptual Questions) 1 2 3 4 5 6 7 8 9 ®10 11 12 ANSWER KEY 13 14 15 Ans. 2 3 4 4 3 3 1 4 1 1 1 4 2 1 4 Que. 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Ans. 4 4 1 1 3 1 3 2 2 4 2 2 4 2 1 Que. 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 Ans. 1 1 2 3 4 2 2 2 3 1 1 1 2 3 4 Que. 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Ans. 3 4 3 1 1 2 3 3 1 3 2 2 1 4 2 Que. 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 Ans. 4 3 2 2 1 4 3 2 3 3 4 1 2 2 2 Que. 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 Ans. 4 1 4 1 4 1 1 2 3 1 3 4 1 2 4 Que. 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 Ans. 2 4 2 1 2 4 4 2 2 2 4 4 1 2 2 Que. 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 Ans. 3 2 3 4 4 4 1 3 2 1 3 1 3 2 2 Que. 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 Ans. 2 2 3 1 1 1 2 4 2 3 2 3 2 3 4 Que. 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 Ans. 3 1 1 2 4 4 3 2 1 3 2 2 3 3 2 Que. 151 152 153 154 155 156 157 158 Ans. 1 4 4 2 2 1 4 4 252  Chemistry : Chemical Thermodynamics and Energetics ® Pre-Medical EXERCISE-II (Previous Year Questions) AIPMT/NEET AIPMT 2014 NEET(UG) 2017 1. For the reaction : X2O4() → 2XO2(g) 6. For a given reaction, ∆H = 35.5 kJ mol–1 and ∆U = 2.1 kCal, ∆S = 20 cal K–1 at 300 K ∆S= 83.6 JK–1mol–1. The reaction is spontaneous Hence ∆G is :- at : (Assume that ∆H and ∆S do not vary with (1) 2.7 kCal tempearature) (2) – 2.7 kCal (1) T > 425 K (3) 9.3 kCal (2) All temperatures (4) – 9.3 kCal (3) T > 298 K TD0228 (4) T < 425 K AIPMT 2015 TD0242 2. Which of the following statements is correct for 7. A gas is allowed to expand in a well insulated ® a reversible process in a state of equilibrium ? container against a constant external pressure of (1) ∆G = 2.30 RT log K 2.5 atm from an initial volume of 2.50 L to a (2) ∆Gº = –2.30 RT log K final volume of 4.50 L. The change in internal (3) ∆Gº = 2.30 RT log K (4) ∆G = –2.30 RT log K energy ∆U of the gas in joules will be:- TD0230 (1) –500 J (2) –505 J (3) +505 J (4) 1136.25 J Re-AIPMT 2015 3. The enthalpy of combustion of carbon to CO2 is TH0243 –1 –393.5 kJ mol. The heat exchange in the NEET (UG) 2018 formation of 35.2 g of CO2 from carbon and 8. The bond dissociation enthalpies of X2, Y2 and oxygen gas is: (1) –630 kJ (2) –3.15 kJ XY are in the ratio of 1 : 0.5 : 1. ∆H for the (3) –315 kJ (4) +315 kJ –1 formation of XY is –200 kJ mol. The bond TC0231 dissociation enthalpy of X2 will be NEET-I 2016 –1 (1) 200 kJ mol (2) 100 kJ mol–1 4. The correct thermodynamic conditions for the spontaneous reaction at all temperatures is (3) 800 kJ mol–1 (4) 400 kJ mol–1 (1) ∆H > 0 and ∆S > 0 TC0248 (2) ∆H > 0 and ∆S < 0 NEET(UG) 2019 (3) ∆H < 0 and ∆S > 0 9. Under isothermal condition, a gas at 300 K (4) ∆H < 0 and ∆S < 0 expands from 0.1L to 0.25L against a constant TD0235 external pressure of 2 bar. The work done by the NEET-II 2016 gas is :- [Given that 1L bar = 100 J] (1) –30 J (2) 5kJ (3) 25 J (4) 30 J 5. For a sample of perfect gas when its pressure is TC0310 changed isothermally from pi to pf, the entropy change is given by NEET(UG) 2019 (Odisha) 10. –3 3 An ideal gas expands isothermally from 10 m p  p  (1) ∆S = nRT ln  f  (2) ∆S = RT ln  i  to 10–2 m3 at 300 K against a constant pressure  pi   pf  5 –2 of 10 Nm. The work, in the process is :- p  p  (1) +270 kJ (2) –900 J (3) ∆S = nR ln  f  (4) ∆S = nR ln  i   pi   pf  (3) +900 kJ (4) –900 kJ TD0236 TC0311 253  ® Chemistry : Chemical Thermodynamics and Energetics Pre-Medical 11. Reversible expansion of an ideal gas under 16. At standard conditions, if the change in the enthalpy isothermal and adiabatic conditions are as shown for the following reaction is –109 kJ mol –1 in the figure. A(PA, VA, TA) H2(g) + Br2(g) → 2HBr(g) Given that bond enthalpy of H2 and Br2 is 435 kJ mol–1 and 192 kJ mol–1, respectively, P B(PB, VB, TB) what is the bond enthalpy (in kJ mol–1) of HBr? C(PC, VC, TC) (1) 368 (2) 736 (3) 518 (4) 259 V TC0351 AB → Isothermal expansion NEET (UG) 2021 AC → Adiabatic expansion Which of the following options is not correct ? 17. Which one among the following is the correct (1) ∆Sisothermal > ∆Sadiabatic (2) TA = TB option for right relationship between CP and CV (3) Wisothermal > Wadiabatic (4) Tc > TA for one mole of ideal gas ? TC0312 ® (1) CP+CV=R NEET (UG) 2020 (2) CP–CV=R 12. The correct option for free expansion of an ideal (3) CP = RCV gas under adiabatic condition is : (4) CV=RCP (1) q > 0, ∆T > 0 and w > 0 (2) q = 0, ∆T = 0 and w = 0 TH0352 (3) q = 0, ∆T < 0 and w > 0 18. For irreversible expansion of an ideal gas under (4) q < 0, ∆T = 0 and w = 0 isothermal condition, the correct option is : TD0347 (1) ∆U = 0, ∆Stotal = 0 13. Hydrolysis of sucrose is given by the following (2) ∆U ≠ 0, ∆Stotal ≠ 0 reaction. (3) ∆U = 0, ∆Stotal ≠ 0 Sucrose + H2O  Glucose + Fructose (4) ∆U ≠ 0, ∆Stotal = 0 If the equilibrium constant (Kc) is 2 × 1013 at TC0353 300K, the value of ∆rG at the same 19. For the homogeneous reactions : temperature will be: xA + yB → Y + mZ –1 –1 13 (1) –8.314 J mol K × 300 K × ln(4 × 10 ) ∆H = – 30 kJ mol–1, ∆S = – 100 J K–1 mol–1. At (2) –8.314 J mol–1 K–1 × 300 K × ln(2 × 1013) –1 –1 13 what temperature the reaction is at equilibrium? (3) 8.314 J mol K × 300 K × ln(2 × 10 ) –1 –1 13 (1) 50°C (2) 250°C (3)100 K (4) 27°C (4) 8.314 J mol K × 300 K × ln(3 × 10 ) TH0356 TD0348 NEET (UG) 2022 14. For the reaction 2Cl(g) → Cl2(g), the correct 20. Which of the following p-V curve represents option is: (1) ∆rH < 0 and ∆rS < 0 maximum work done ? (2) ∆rH > 0 and ∆rS > 0 (3) ∆rH > 0 and ∆rS < 0 Isothermal Isothermal (4) ∆rH < 0 and ∆rS > 0 p p TD0349 (1) (2) NEET (UG) 2020 (COVID-19) V V 15. If for a certain reaction ∆rH is 30 kJ mol at 450 –1 K, the value of ∆rS (in JK–1 mol–1) for which the Isothermal Isothermal same reaction will be spontaneous at the same p p temperature is (3) (4) (1) 70 (2) –33 V V (3) 33 (4) –70 TD0350 TH0357 254  Chemistry : Chemical Thermodynamics and Energetics ® Pre-Medical NEET (UG) 2022 (OVERSEAS) NEET (UG) 2023 21. The work done when 1 mole of a gas 23. Which amongst the following options is the correct relation between change in enthalpy and expands reversibly and isothermally from change in internal energy? pressure of 5 atm to 1 atm at 300 K is (1) ∆H = ∆U + ∆ng RT (2) ∆H – ∆U = – ∆nRT (Given log 5 = 0.6989 and R = 8.314 J K mol ) –1 –1 (3) ∆H + ∆U = ∆nR (4) ∆H = ∆U – ∆ngRT (1) 150 J TH0360 (2) + 4014.6 J NEET (UG) 2023 (Manipur) (3) –4014.6 J 24. Consider the following reaction :- (4) zero J TH0358 2H2(g) + O2(g) → 2H2O(g) ∆rH° = –483.64 kJ. Re-NEET (UG) 2022 What is the enthalpy change for decomposition 22. One mole of an ideal gas at 300 K is expanded of one mole of water ? (Choose the right ® isothermally from 1 L to 10 L volume. ∆U for option). –1 –1 this process is (Use R = 8.314 J K mol ) (1) 120.9 kJ (2) 241.82 kJ (1) 1260 J (3) 18 kJ (4) 100 kJ (2) 2520 J TC0361 (3) 5040 J (4) 0 J TH0359 EXERCISE-II (Previous Year Questions) ANSWER KEY Que. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Ans. 2 2 3 3 4 1 2 3 4 2 4 2 2 1 1 Que. 16 17 18 19 20 21 22 23 24 Ans. 1 2 3 4 1 3 4 1 2 255  ® Chemistry : Chemical Thermodynamics and Energetics Pre-Medical EXERCISE-III (Analytical Questions) Master Your Understanding 1. Consider the reaction : N2 + 3H2 → 2NH3 carried 6. Which of the following pairs of a chemical out at constant temperature and pressure. If ∆H reaction is certain to result in a spontaneous and ∆U are the enthalpy and internal energy reaction.? changes for the reaction, which of the following (1) endothermic and decreasing disorder expressions is true ? (2) exothermic and increasing disorder (1) ∆ H < ∆ U (2) ∆ H > ∆ U (3) endothermic and increasing disorder (3) ∆ H = 0 (4) ∆ H = ∆ U (4) exothermic and decreasing disorder TH0258 TD0265 2. For an ideal gas in a reversible process at T = 7. The conversion A to B is carried out by the 300K, the volume is increased from Vi = 1L to following path : Vf = 10L. Calculate ∆H if the process is ® isothermal - C D Given : ∆S(A → C) = 50 e.u. , (1) 11.47 kJ (2) 4.98 kJ A B (3) 0 (4) –11.47 kJ TH0259 ∆S(C → D) = 30 e.u., ∆S(B → D) = 20 e.u. 3. A piston filled with 0.04 mol of an ideal gas where e.u. is entropy unit then ∆S(A → B) is expands reversibly from 50.0 mL to 375 mL at a (1) + 100 e.u. (2) + 60 e.u. constant temperature of 37.0°C. As it does so, it (3) – 100 e.u. (4) – 60 e.u. absorbs 208 J of heat. The values of q and w for TD0266 the process will be :- –1 –1 8. In a fuel cell methanol is used as fuel and oxygen (R = 8.314 J mol K ) (ln7.5 = 2.01) (1) q = + 208 J, w = – 208 J gas is used as an oxidizer. The reaction is (2) q = – 208 J, w = – 208 J 3 CH3OH() + O2(g) → CO2(g) + 2H2O() (3) q = – 208 J, w = + 208 J 2 (4) q = + 208 J, w = + 208 J At 298 K standard Gibb's energies of formation TH0261 for CH3OH(), H2O() and CO2(g) are –166.2, 4. The entropy change involved in the isothermal –1 reversible expansion of 2 moles of an ideal gas –237.2 and –394.4 kJ mol respectively. 3 from a volume of 10 dm to a volume of 100 dm 3 If standard enthalpy of combustion of methanol is – at 27°C is :- 726 kJ mol–1, efficiency of the fuel cell will be –1 –1 –1 –1 (1) 32.3 J mol K (2) 42.3 J mol K (1) 90% (2) 97% (3) 80% (4) 87% –1 –1 (3) 38.3 J mol K (4) 35.8 J mol–1 K–1 TC0268 TD0262 9. Identify the correct statement regarding a 5. For the process H2O() (1 bar , 373K) → H2O(g) sponateous process :- (1) For a spontaneous process in an isolate system,