Thermodynamics PYQs Set 1 (PDF)

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Mere Teacher · Previous Year Questions JEE Main Chemistry · Thermodynamics · Set 1 (Q1-30)
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1. $Choose the correct option for free expansion of an ideal gas under adiabatic condition from the following:$ (1) $q = 0, Δ T \neq = 0, w = 0$ (2) $q = 0, Δ T < 0, w \neq = 0$ (3) $q \neq = 0, Δ T = 0, w = 0$ (4) $q = 0, Δ T = 0, w = 0$ 2. $The species which by definition has ZERO standard molar enthalpy of formation at 298 K is :$ (1) $B r_{2} (g)$ (2) $C l_{2} (g)$ (3) $H_{2} O(g)$ (4) $C H_{4} (g)$ 3. $Given that C + O_{2} \to C O_{2}, Δ H^{o} = - xkJ 2 CO + O_{2} \to 2 C O_{2}, Δ H^{o} = - ykJ The enthalpy of formation of carbon monoxide will be$ (1) $\frac{y - 2 x}{2}$ (2) $2 x - y$ (3) $y - 2 x$ (4) $\frac{2 x - y}{2}$ 4. $Which of the following statements is correct for the spontaneous adsorption of a gas?$ (1) $Δ S is negative and, therefore Δ H should be highly positive.$ (2) $Δ S is negative and therefore, Δ H should be highly negative.$ (3) $Δ S is positive and therefore, Δ H should be negative.$ (4) $Δ S is positive and therefore, Δ H should also be highly positive.$ 5. $Match the LIST-I with LIST-II List-I Isothermal process for ideal gas system (A) Reversible expansion (B) Free expansion (C) Irreversible expansion (D) Irreversible compression List-II Work done (V_{f} > V_{i}) (I) w = 0 (II) w=-nRTlnVfVi (III) w = - p_{ex} (V_{f} - V_{i}) (IV) w = - p_{ex} (V_{i} - V_{f}) Choose the correct answer from the options given below:$ (1) $A-I, B-III, C-II, D-IV$ (2) $A-II, B-I, C-III, D-IV$ (3) $A-IV, B-I, C-III, D-II$ (4) $A-IV, B-II, C-III, D-I$ 6. $A vessel contains 100 liters of a liquid X. Heat is supplied to the liquid in such a fashion that, Heat given = change in enthalpy. The volume of the liquid increases by 2 liters. If the external pressure is one atm, and 202.6 Joules of heat were supplied then, [U - total internal energy]$ (1) $∆ U = 0, ∆ H = 0$ (2) $∆ U = + 202. 6J, ∆ H = + 202.6 J$ (3) $∆ U = - 202.6J, ∆ H = - 202.6J$ (4) $∆ U = 0, ∆ H = + 202.6J$ 7. $For a reaction A + B \to products, Δ H is - 84.2 kJ and Δ S is - 200 J K^{- 1} . Calculate the highest value of temperature so that the reaction will proceed in forward direction.$ (1) $421 K$ (2) $237 K$ (3) $168 K$ (4) $273 K$ 8. $For which of the following systems, the difference between Δ H and Δ U is not significant? (i) Solids (ii) gases (iii) Mixture of gases and liquids (iv) Liquids$ (1) $(i) and (iv)$ (2) $(i), (iii) and (iv)$ (3) $(ii) and (iv)$ (4) $(ii) and (iii)$ 9. $Calculate the PV type of work for the following reaction at 1 bar pressure. C_{3} H_{6 (g)} (150 mL) + HCl_{(g)} (150 mL) ⟶ C_{3} H_{7} Cl_{(g)} (150 mL)$ (1) $5.2 J$ (2) $10.21 J$ (3) $15.00 J$ (4) $18.2 J$ 10. $Enthalpy change for the reaction, 4 H_{(g)} \to 2 H_{2 (g)} is - 869.6 kJ The dissociation energy of H - H bond is$ (1) $- 434.8 kJ$ (2) $- 869.6 kJ$ (3) $+ 434.8 kJ$ (4) $+ 217.4 kJ$ 11. $For vaporization of water at 1 atmospheric pressure, the values of Δ H and Δ S are 40.63 kJmo l^{- 1} and 108.8 J K^{- 1} mo l^{- 1}, respectively The temperature when Gibb’s energy change (G) for this transformation will be zero, is$ (1) $273.4 K$ (2) $393.4 K$ (3) $373.4 K$ (4) $293.4 K$ 12. $For which among the following reactions, change in entropy is less than zero?$ (1) $Sublimation of iodine$ (2) $Dissociation of hydrogen$ (3) $Formation of water$ (4) $Thermal decomposition of calcium carbonate$ 13. $A certain engine which operates in a carnot cycle absorbs 3.347 kJ at 400ºC, how much work is done by the engine per cycle ? The temperature of sink is 100ºC.$ (1) $1.49 kJ$ (2) $2.51 kJ$ (3) $1.85 kJ$ (4) $2.98 kJ$ 14. $Which among the following colligative properties is useful to determine molar masses of very expensive solutes?$ (1) $Freezing point depression$ (2) $Osmotic pressure$ (3) $Vapour pressure lowering$ (4) $Boiling point elevation$ 15. $Calculate the entropy change (\frac{J}{mol} K) of the given reaction. The molar entropies [J/K-mol] are given in brackets after each substance. 2 PbS (s) (91.2) + 3 O_{2} (g) (205.1) ⟶ 2 PbO (s) (66.5) + 2 SO_{2} (g) (248.2)$ (1) $-113.5$ (2) $-168.3$ (3) $+72.5$ (4) $-149.2$ 16. $Enthalpy of sublimation of iodine is 24 cal g^{- 1} at 200° C . If specific heat of I_{2} (s) and I_{2} (vap) are 0.055 and 0.031 cal g^{- 1} K^{- 1} respectively, then enthalpy of sublimation of iodine at 250° C in cal g^{- 1} is:$ (1) $2.85$ (2) $5.7$ (3) $22.8$ (4) $11.4$ 17. $Which one of the following equations does not correctly represent the first law of thermodynamics for the given processes involving an ideal gas? (Assume non-expansion work is zero)$ (1) $Cyclic process: q = - w$ (2) $Adiabatic process: Δ U = - w$ (3) $Isochoric process: Δ U = q$ (4) $Isothermal process: q = - w$ 18. $Under isothermal condition, a gas at 300 K expands from 0.1 L to 0.25 L against a constant external pressure of 2 bar. The work done by the gas is (Given that 1 L bar = 100 J)$ (1) $-30 J$ (2) $5 kJ$ (3) $25 J$ (4) $30J$ 19. $For a reversible spontaneous change Δ S is$ (1) $\frac{Δ E}{T}$ (2) $\frac{P Δ V}{T}$ (3) $\frac{q}{T}$ (4) $RT log K$ 20. $The reaction, MgO(s) + C(s) \to Mg(s) + CO(g), for which D_{r} H° = +491.1 kJ m o l^{-1} and D_{r} S° = 198.0 J K^{-1} m o l^{-1}, is not feasible at 298 K. Temperature above which reaction will be feasible is:$ (1) $2380.5 K$ (2) $1890.0 K$ (3) $2040.5 K$ (4) $2480.3 K$ 21. $If Δ H is the change in enthalpy and Δ E, the change in internal energy accompanying a gaseous reaction, then$ (1) $Δ H is always greater than Δ E$ (2) $Δ H < Δ E only ifthe number of moles of the products is greater than the number of moles of the reactants$ (3) $Δ H is always less than Δ E$ (4) $Δ H < Δ E only if the number of moles of products is less than the number of moles of the reactants.$ 22. $When 5litres of a gas mixture of methane and propane is perfectly combusted at 0^{o} C and 1 atmosphere, 16 litres of oxygen at the same temperature and pressure is consumed. The amount of heat released from this combustion in kJ (Δ H_{comb} . (C H_{4}) = 890 kJmo l^{- 1}, K_{comb} (C_{3} H_{8}) = 2220 kJmo l^{- 1}) is$ (1) $38$ (2) $317$ (3) $477$ (4) $32$ 23. $From the following bond energies: H—H bond energy: 431.37 kJ mol^{- 1} C=C bond energy: 606.10 kJ mol^{- 1} C—C bond energy: 336.49 kJ mol^{- 1} C—H bond energy: 410.50 kJ mol^{- 1} Enthalpy for the reaction, C H_{2} = C H_{2} + H_{2} \to C H_{3} - C H_{3} will be$ (1) $- 243.6 kJmo l^{- 1}$ (2) $- 120.0 kJmo l^{- 1}$ (3) $553.0 kJmo l^{- 1}$ (4) $1523.6 kJmo l^{- 1}$ 24. $The plot of log_{10} K vs \frac{1}{T} gives a straight line. The intercept and slope respectively are (where K is equilibrium constant).$ (1) $\frac{Δ S ^{\circ}}{2 \cdot 303 R}, - \frac{Δ H ^{\circ}}{2 \cdot 303 R}$ (2) $- \frac{Δ S ^{\circ} R}{2 \cdot 303}, \frac{Δ H ^{\circ} R}{2 \cdot 303}$ (3) $\frac{2 \cdot 303 R}{Δ H ^{\circ}}, \frac{2 \cdot 303 R}{Δ S ^{\circ}}$ (4) $- \frac{Δ H ^{\circ}}{2 \cdot 303 R}, \frac{Δ S ^{\circ}}{2 \cdot 303 R}$ 25. $Mathematical equation of first law of thermodynamics for isochoric process is$ (1) $Δ U = q_{v}$ (2) $q = - W$ (3) $- Δ U = q_{v}$ (4) $Δ U = W$ 26. $Which of the following is the correct equation?$ (1) $Δ U = Δ W + Δ Q$ (2) $Δ U = Δ Q - W$ (3) $Δ W = Δ U + Δ Q$ (4) $None of these$ 27. $Bond enthalpies of A_{2}, B_{2} and AB are in the ratio 2:1:2. If bond enthalpy of formation of AB is 100 kJ mol^{- 1} . The bond enthalpy of B_{2} is$ (1) $100 kJ mol^{- 1}$ (2) $200 kJ mol^{- 1}$ (3) $500 kJ mol^{- 1}$ (4) $150 kJ mol^{- 1}$ 28. $Thermodynamic standard conditions of temperature and pressure are$ (1) $0^{\circ} C and 101.3kPa$ (2) $298 K and 1 atm$ (3) $273 K and 101.3kPa$ (4) $0^{\circ} C and 1 atm.$ 29. $For the reaction H_{2} F_{2} (g) \to H_{2} (g) + F_{2} (g) ∆ U = -59.6 kJ m o l^{- 1} at 27°C. The enthalpy change for the above reaction is (-) ___kJ m o l^{- 1} [nearest integer] Given : R = 8.314 J K^{- 1} m o l^{- 1}$ 30. $The molar heat capacity for an ideal gas at constant pressure is 20.785 J K^{- 1} m o l^{- 1} . The change in internal energy is 5000 J upon heating it from 300K to 500K. The number of moles of the gas at constant volume is___[Nearest integer](Given: R = 8.314 J K^{- 1} m o l^{- 1})$