Thermodynamics PYQs Set 17 (PDF)

Set 17 of 18 · Questions 481-510 of 511

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Mere Teacher · Previous Year Questions JEE Main Chemistry · Thermodynamics · Set 17 (Q481-510)
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481. $For the process H_{2} O (l) (1 bar, 373 K) \to H_{2} O (g) (1 bar, 373 K), the correct set of thermodynamic parameters is :$ (1) $Δ G = 0, Δ S = + v e$ (2) $Δ G = 0, Δ S = - v e$ (3) $Δ G = + v e, Δ S = 0$ (4) $Δ G = - v e, Δ S = + v e$ 482. $Δ U equal to:$ (1) $Isobaric work$ (2) $Adiabatic work$ (3) $Isothermal work$ (4) $Isochoric work$ 483. $The spontaneous flow of heat is always$ (1) $From low to high pressure$ (2) $From high to high pressure$ (3) $Unidirectional from lower temperature to higher temperature$ (4) $Unidirectional from the higher to lower temperature$ 484. $The incorrect expression among the following is:$ (1) $\frac{Δ G _{sy s t e m}}{Δ S _{t o t a l}} = - T (at constant P)$ (2) $ln K = \frac{Δ H ^{0} - T Δ S ^{0}}{R T}$ (3) $K = e^{- Δ G^{0} / R T}$ (4) $For isothermal process W_{r e v er s ib l e} = - n R T ln \frac{V _{f}}{V _{i}}$ 485. $Two blocks of the same metal having same mass and at temperature T_{1} and T_{2}, respectively, are brought in contact with each other and allowed to attain thermal equilibrium at constant pressure. The change in entropy, Δ S, for this process is:$ (1) $2 C_{P} ln (\frac{T _{1} + T _{2}}{4 T _{1} T _{2}})$ (2) $2 C_{P} ln [\frac{( T _{1} + T _{2} ) ^{2}}{T _{1} T _{2}}]^{1/2}$ (3) $C_{P} ln [\frac{( T _{1} + T _{2} ) ^{2}}{4 T _{1} T _{2}}]$ (4) $2 C_{P} ln [\frac{T _{1} + T _{2}}{2 T _{1} T _{2}}]$ 486. $The bond energy (in kcal m o l^{-1}) of a C-C single bond is approximately :$ (1) $1$ (2) $10$ (3) $100$ (4) $1000$ 487. $Then entropy (Sº) of the following substances are: C H_{4} (g) 186.2 J K^{-1} m o l^{-1}, O_{2} (g) 205.0 J K^{-1} m o l^{-1} C O_{2} (g) 213.6 J K^{-1} m o l^{-1}, H_{2} O(l) 69.9 J K^{-1} m o l^{-1} The entropy change (DSº) for the reaction C H_{4} (g) + 2 O_{2} (g) ® C O_{2} (g) + 2 H_{2} O(l) is :$ (1) $-312.5 J K^{-1} m o l^{-1}$ (2) $-242.3 J K^{-1} m o l^{-1}$ (3) $-108.1 J K^{-1} m o l^{-1}$ (4) $-37.6 J K^{-1} m o l^{-1}$ 488. $When a solid is converted into liquid, entropy$ (1) $Becomes zero$ (2) $Remains the same$ (3) $Decreases$ (4) $Increases$ 489. $For a reaction taking place in a container in equilibrium with its surroundings, the effect of temperature on its equilibrium constant K in terms of change in entropy is described by$ (1) $With increase in temperature, the value of K for endothermic reaction increases because unfavourable change in entropy of the surroundings decreases$ (2) $With increase in temperature, the value of K for exothermic reaction decreases because favourable change in entropy of the surroundings decreases$ (3) $With increase in temperature, the value of K for endothermic reaction increases because the entropy change of the system is negative$ (4) $With increase in temperature, the value of K for exothermic reaction decreases because the entropy change of the system is positive$ 490. $The standard enthalpy of formation (D_{f} H º_{298}) for methane, C H_{4} is -74.9 kJ m o l^{-1} . In order to calculate the average energy given out in the formation of a C-H bond from this it is necessary to know which one of the following?$ (1) $the dissocation energy of the hydrogen molecule, H_{2} .$ (2) $the first four ionisation energies of carbon.$ (3) $the dissociation energy of H_{2} and enthalpy of sublimation of carbon (graphite).$ (4) $the first four ionisation energies of carbon and electron affinity of hydrogen$ 491. $The correct statement regarding entropy is$ (1) $at absolute zero temperature, entropy of a perfectly crystalline solid is zero$ (2) $at absolute zero temperature, the entropy of a perfectly crystalline substance is + ve$ (3) $at absolute zero temperature, the entropy of all crystalline substances is zero$ (4) $at 0^{\circ} C, the entropy of a perfect crystalline solid is zero.$ 492. $Which of the following equations are correct?(A) U = H - PV (B) G = H - TS (C) U = q + W$ (1) $A, B and C$ (2) $A and B only$ (3) $A and C only$ (4) $B and C only$ 493. $Which of the following reactions is associated with the most negative change in entropy?$ (1) $2SO2 (g) + O2 (g) 2SO3 (g)$ (2) $C_{2} H_{4} (g) + H_{2} (g) C_{2} H_{6} (g)$ (3) $C (s, graphite) + O_{2} C O_{2} (g)$ (4) $3 C_{2} H_{2} (g) C_{6} H_{6} (ℓ)$ 494. $If the bond energies of H - H, Br - Br and H - Br are 433, 192 and 364 kl mol^{- 1} respectively, then Δ H^{\circ} for the reaction: H_{2 (g)} + Br_{2 (g)} ⟶ 2 HBr_{(g)} is$ (1) $- 261 kJ$ (2) $+ 103 k$ (3) $+ 261 kJ$ (4) $- 103 kJ$ 495. $The molar heat capacity (C_{p}) of C D_{2} O is 10 cals at 1000 K. The change in entropy associated with cooling of 32 g of C D_{2} O vapour from 1000 K to 100 K at constant pressure will be: (D = deuterium, at. mass = 2 u)$ (1) $23.03 cal d e g^{-1}$ (2) $- 23.03 cal d e g^{-1}$ (3) $2.303 cal d e g^{-1}$ (4) $- 2.303 cal d e g^{-1}$ 496. $Given R = 8.314 J K^{- 1} mol^{- 1}, the work done during combustion of 0.090 kg of ethane (molar mass = 30) at 300 K is$ (1) $- 18.7 kJ$ (2) $18.7 kJ$ (3) $6.234 kJ$ (4) $- 6.234 kJ$ 497. $Third law of thermodynamics states that:$ (1) $the entropy of a perfectly crystalline pure substance at zero K is zero.$ (2) $absolute entropy of hydrogen ion is zero at zero K.$ (3) $net change in entropy in conversion H_{2 (g)} (130 K) ® H_{2 (g)} (200K) is zero.$ (4) $entropy generally decrease in combustion reactions$ 498. $In which state, the matter have highest entropy$ (1) $Solid$ (2) $Liquid$ (3) $Gas$ (4) $Equal in all$ 499. $Which of the following statements is true?$ (1) $The total entropy of the universe remains constant.$ (2) $The total entropy of the universe is continuously decreasing.$ (3) $The total energy of the universe is continuously decreasing.$ (4) $The total energy of the universe remains constant.$ 500. $At T (K) 2 mole of an ideal gas is allowed to expand reversibly and isothermally from a pressure of 10 atmospheres to 1 atmosphere. The work done (in kJ) is (R = 8.3 J K^{- 1} mol^{- 1})$ (1) $- 3.82 \times 10^{- 1} \times T$ (2) $- 4.82 \times 10^{- 1} \times T$ (3) $- 2.82 \times 10^{- 2} \times T$ (4) $- 3.82 \times 10^{- 2} \times T$ 501. $At 373 K steam and water are in equilibrium and ∆ H = 40.98 k J m o l^{- 1} what will be ∆ S for conversion of water into steam?$ (1) $109.8 J K^{- 1} m o l^{- 1}$ (2) $31 J K^{- 1} m o l^{- 1}$ (3) $21.98 J K^{- 1} m o l^{- 1}$ (4) $326 J K^{- 1} m o l^{- 1}$ 502. $Among the following given substances, the one with zero Δ_{f} H^{\circ} is$ (1) $Diamond$ (2) $Graphite$ (3) $Fullerene$ (4) $Bituminous coal$ 503. $A reaction is at equilibrium at 10 0^{o} C and the enthalpy change for the reaction is 42.6 k J m o l^{- 1} What will be the value of ∆ S in J K^{- 1} m o l^{- 1 ?}$ (1) $120$ (2) $426.2$ (3) $373.1$ (4) $114.2$ 504. $Enthalpy change for the process H_{2} O(ice) ⇌ H_{2} O(water) is 6.01 k J m o l^{- 1} The entropy change of 1 mole of ice at its melting point will be.$ (1) $12 J K^{- 1} m o l^{- 1}$ (2) $22 J K^{- 1} m o l^{- 1}$ (3) $100 J K^{- 1} m o l^{- 1}$ (4) $30 J K^{- 1} m o l^{- 1}$ 505. $For a reaction: X \to Y + Z Absolute entropies are X = 120 J K^{- 1} m o l^{- 1}, Y = 213.8 J K^{- 1} m o l^{- 1} an d Z = 197.9 J K^{- 1} m o l^{- 1} will be the enetropy change at 298 K and 1 atm?$ (1) $291.7 J K^{- 1}$ (2) $255 J K^{- 1}$ (3) $213.8 J K^{- 1}$ (4) $257.3 J K^{- 1}$ 506. $Which of the following reactions will have the value of ∆ S with a negative sign?$ (1) $H_{2} O_{(l)} \to H_{2} O_{(g)}$ (2) $2 S O_{2 (g)} + O_{2 (g)} \to 2 S O_{3 (s)}$ (3) $C l_{2 (g)} \to 2 C l_{(g)}$ (4) $C a C O_{3 (s)} \to C a O_{(s)} + C O_{2 (g)}$ 507. $Which of the following expressions regarding entropy is not correct?$ (1) $∆ s_{sy s t e m} = \frac{q}{T}$ (2) $Δ s_{system} = Δ s_{total} + Δ s_{surrouding}$ (3) $Δ s = S_{final} - S_{initial}$ (4) $Δ s_{total} = Δ s_{system} + Δ s_{surrounding}$ 508. $When a liquid boils, there is$ (1) $An increase in entropy$ (2) $A decrease in entropy$ (3) $An increase in heat of vaporization$ (4) $An increase in free energy$ 509. $4.0 L of an ideal gas is allowed to expand isothermally into vacuum until the total volume is 20 L. The amount of heat absorbed in this expansion is___________L atm.$ 510. $While performing a thermodynamics experiment, a student made the following observations, HC1 + NaOH \to NaCl + H_{2} O ∆ H = -57.3 kJ m o l^{- 1} C H_{3} COOH + NaOH \to C H_{3} COONa + H_{2} O ∆ H = -55.3 kJ m o l^{- 1} The enthalpy of ionization of C H_{3} COOH as calculated by the student is ______ kJ m o l^{- 1} . (nearest integer)$