Thermodynamics PYQs Set 2 (PDF)

Set 2 of 18 · Questions 31-60 of 511

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Mere Teacher · Previous Year Questions JEE Main Chemistry · Thermodynamics · Set 2 (Q31-60)
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31. $5 moles of an ideal gas at 100 K are allowed to undergo reversible compression till its temperature becomes 200 K . If C_{V} = 28 J K^{- 1} mol^{- 1} calculate Δ U and Δ pV for this process. (R = 8.0 J K^{- 1} mol^{- 1})$ (1) $Δ U = 14 kJ; Δ (pV) = 18 kJ$ (2) $Δ U = 14 kJ; Δ (pV) = 0.8 kJ$ (3) $Δ U = 14 kJ; Δ (pV) = 4 kJ$ (4) $Δ U = 14 kJ; Δ (pV) = 8.0 kJ$ 32. $Standard enthalpy of vaporisation Δ_{vap} H^{o} for water at 100 C is 40.66 kJmo l^{- 1} . The internal energy of vaporisation of water at 100 C (in kJmo l^{- 1}) is(Assume water vapour to behave like an ideal gas)$ (1) $+ 37.56$ (2) $- 43.76$ (3) $+ 43.76$ (4) $+ 40.66$ 33. $Which of the following endothermic processes are spontaneous?$ (1) $Melting of ice$ (2) $Evaporation of water$ (3) $Heat of combustion$ (4) $Both (a) and (b)$ 34. $At what temperature liquid water will be in equilibrium with water vapour? ∆ H_{v a p} = 40.73 k J m o l^{- 1}, ∆ S_{v a p} = 0.109 k J K^{- 1} m o l^{- 1}$ (1) $282.4 K$ (2) $373.6 K$ (3) $100 K$ (4) $400 K$ 35. $Pb O_{2} \to PbO; Δ G_{298} < 0 Sn O_{2} \to SnO; Δ G_{298} > 0 Most probable oxidation state of Pb and Sn will be$ (1) $P b^{4 +}, S n^{4 +}$ (2) $P b^{4 +}, S n^{2 +}$ (3) $P b^{2 +}, S n^{2 +}$ (4) $P b^{2 +}, S n^{4 +}$ 36. $Which among the following is a feature of adiabatic expansion?$ (1) $Δ V < 0$ (2) $Δ U < 0$ (3) $Δ U > 0$ (4) $Δ T = 0$ 37. $The criterion for a spontaneous process is$ (1) $Δ G > 0$ (2) $Δ G < 0$ (3) $Δ G = 0$ (4) $Δ S_{total} < 0$ 38. $Enthalpy of formation of CO (g), CO_{2} (g) are - 110, - 393 kJ mol^{- 1} respectively. The enthalpy of combustion of CO (in kJ mol^{- 1}) is$ (1) $-283.0$ (2) $-110.5$ (3) $504$ (4) $-221.2$ 39. $At 60^{\circ} C, dinitrogen tetroxide is 50 % dissociated. Find it's standard free energy change at this temperature and one atmosphere. [Given log 1.33 = 0.1239]$ (1) $- 650 J mol^{- 1}$ (2) $- 830 J mol^{- 1}$ (3) $- 790 J mol^{- 1}$ (4) $- 875 J mol^{- 1}$ 40. $Given (i) 2 F e_{2} O_{3} (s) \to 4Fe(s) + 3 O_{2} (g) ; D_{r} G° = + 1487.0 kJ m o l^{-1} (ii) 2CO(g) + O_{2} (g) \to 2 C O_{2} (g) ; D_{r} G° = -514.4 kJ m o l^{-1} Free energy change, D_{r} G° for the reaction 2 F e_{2} O_{3} (s) + 6CO(g) \to 4Fe(s) + 6 C O_{2} (g) will be$ (1) $-112.4 kJ m o l^{-1}$ (2) $-56.2 kJ m o l^{-1}$ (3) $-168.2 kJ m o l^{-1}$ (4) $-208.0 kJ m o l^{-1}$ 41. $The heat of atomisation of methane and ethane are ' x^{’} kJmol^{- 1} and ' y^{’} kJmol^{- 1} respectively. The longest wavelength (λ) of light capable of breaking the C - C bond can be expressed in SI unit as:$ (1) $\frac{N _{A} hc}{250 ( 4 y - 6 x )}$ (2) $\frac{hc}{1000} (\frac{y - 6 x}{4})^{- 1}$ (3) $\frac{N _{A} hc}{250 ( y - 6 x )}$ (4) $N_{A} hc (y - \frac{6 x}{4})^{- 1}$ 42. $The enthalpy of neutralisation of H C O_{3}^{-} (aq) with strong alkali is - 42 kJ/mole and enthalpy of neutralisation of strong acid with strong alkali is - 56 kJ/equiv. Therefore, enthalpy of dissociation of H C O_{3}^{-} (aq) is-$ (1) $- 98 kJ/mol$ (2) $98 kJ/mol$ (3) $14 kJ/mol$ (4) $24 kJ/mol$ 43. $The enthalpy of formation (Δ H_{f}) of methanol, formaldehyde and water are - 239, - 116 and - 286 kJ mol^{- 1} respectively. The enthalpy change for the oxidation of methanol to formaldehyde and water in kJ is$ (1) $-136$ (2) $-173$ (3) $163$ (4) $-163$ 44. $In the reaction: S + 3/2 O_{2} \to S O_{3} + 2 x kcal and S O_{2} + 1/2 O_{2} \to S O_{3} + y kcal, the heat of formation of S O_{2} is$ (1) $(2 x + y)$ (2) $(x - y)$ (3) $(x + y)$ (4) $(2 x - y)$ 45. $Two moles of an ideal gas are allowed to expand from a volume of 10 dm^{3} to 2 m^{3} at 300 K against a pressure of 101.325 kPa . Calculate the work done.$ (1) $- 201.6 kJ$ (2) $13.22 kJ$ (3) $- 810.6 J$ (4) $- 18.96 kJ$ 46. $C_{6} H_{12} O_{6} (S) + 6 O_{2} (g) \to 6 CO_{2} (g) + 6 H_{2} O (l) What is the Δ U for the same reaction at 300 K (kJ mol^{- 1}) ?$ (1) $-2802.49$ (2) $-2800.00$ (3) $-2814.94$ (4) $+2802.49$ 47. $The heat required to rise the temperature of 54 g of aluminium from 40^{\circ} C to 60^{\circ} C in J is (molar heat capacity of aluminium in this temperature range is 24 J mol^{- 1} K^{- 1}; atomic weight of Al is 27 )$ (1) $480$ (2) $800$ (3) $960$ (4) $1280$ 48. $For the chemical reaction X ⇌ Y the standard reaction Gibbs energy depends on temperature T (in K) as Δ_{r} G^{\circ} (in kJ mol^{- 1}) = 120 - \frac{3}{8} T The major component of the reaction mixture at T is :$ (1) $Y if T = 300 K$ (2) $Y if T = 280 K$ (3) $X if T = 350 K$ (4) $X if T = 315 K$ 49. $S (g) + \frac{3}{2} O_{2} (g) \to SO_{3} (g) + 2 x kcal SO_{2} (g) + \frac{1}{2} O_{2} (g) \to SO_{3} (g) + y kcal The heat of formation of SO_{2} (g) is given by:$ (1) $x + y kcal$ (2) $y - 2 x kcal$ (3) $\frac{2 x}{y} kcal$ (4) $2 x + y kcal$ 50. $The process is spontaneous at the given temperature, if$ (1) $Δ H is + ve and Δ S is -ve$ (2) $Δ H is -ve and Δ S is +ve$ (3) $Δ H is +ve and Δ S is +ve$ (4) $Δ H is +ve and Δ S is equal to zero.$ 51. $Enthalpy of vaporization of benzene is + 35.3 kJ mo l^{- 1} at its boiling point, 8 0^{\circ} C . The entropy change in the transition of the vapour to liquid at its boiling point (in J K^{- 1} mo l^{- 1}) is$ (1) $-441$ (2) $-100$ (3) $+441$ (4) $+100$ 52. $Based on the first law of thermodynamics, which one of the following is correct?$ (1) $For an isochoric process, Δ U = - q$ (2) $For an adiabatic process, Δ U = - w$ (3) $For an isothermal process, q = + w$ (4) $For a cyclic process, q = - w$ 53. $Which of the following does not follow first law of thermodynamics? (W = work; q = heat; Δ U = change in internal energy)$ (1) $W > 0; q > 0; Δ U < 0$ (2) $W = 0; q = 0; Δ U = 0$ (3) $W > 0; q = 0; Δ U > 0$ (4) $W < 0; q < 0; Δ U < 0$ 54. $If the enthalpy change for the transition of liquid water to steam is 30 kJmo l^{- 1} at 2 7^{o} C, the entropy change for the process would be$ (1) $10 J m o l^{- 1} K^{- 1}$ (2) $1.0 J m o l^{- 1} K^{- 1}$ (3) $0.1 J m o l^{- 1} K^{- 1}$ (4) $100 J m o l^{- 1} K^{- 1}$ 55. $When 600 mL of 0.2 M H N O_{3} is mixed with 400 mL of 0.1M NaOH solution in a flask, the rise in temperature of the flask is_______x 1 0^{- 2}^{0} C. (Enthalpy of neutralisation = 57 kJ m o l^{- 1} and Specific heat of water = 4.2 J K^{- 1} g^{- 1}) (Neglect heat capacity of flask)$ 56. $Δ_{vap} H^{⊖} for water is + 40.79 kJ mol^{- 1} at 1 bar and 100^{\circ} C . Change in internal energy for this vapourisation under same condition is kJmol^{- 1} . (Integer answer) (Given R = 8.3 JK^{- 1} mol^{- 1})$ 57. $If 5 moles of an ideal gas expands from 10 L to a volume of 100 L at 300 K under isothermal and reversible condition then work, w, is - x J . The value of x is_______(Given R = 8.314 J K^{- 1} mol^{- 1})$ 58. $If the standard molar enthalpy change for combustion of graphite powder is - 2.48 \times 1 0^{2} k J m o l^{- 1}, the amount of heat generated on combustion of 1g of graphite powder is _____ kJ. (Nearest integer)$ 59. $The entropies of H2(g) and H(g) are 60 and 50 J m o l e^{-1} K^{-1} respectively at 300 K. Using the data given below calculate the bond enthalpy of H2 (g) in Kcal m o l e^{-1} . H2 (g) \to 2H (g) ;ΔGº = 21.6 KJ m o l e^{-1}$ 60. $Calculate the magnitude of free energy in KJ m o l^{-1} when 1 mole of an ionic salt MX (s) is dissolved in water at 27°C. Given Lattice energy of MX = 780 kJ m o l^{-1} Hydration energy of MX = - 775.0 kJ m o l^{-1} Entropy change of dissolution at 27°C = 40 J m o l^{-1} K^{-1}$