Thermodynamics PYQs Set 8 (PDF)

Set 8 of 18 · Questions 211-240 of 511

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Mere Teacher · Previous Year Questions JEE Main Chemistry · Thermodynamics · Set 8 (Q211-240)
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211. $Let us consider an endothermic reaction which is non-spontaneous at the freezing point of water. However, the reaction is spontaneous at boiling point of water. Choose the correct option.$ (1) $Both ΔH and ΔS are (- ve)$ (2) $ΔH is (- ve) but ΔS is (+ ve)$ (3) $ΔH is (+ ve) but ΔS is (- ve)$ (4) $Both ΔH and ΔS are (+ ve)$ 212. $Lattice enthalpy for NaCl is + 788 kJ mol^{- 1} and Δ H^{\circ}_{hyd} = - 784 kJ mol^{- 1} . Enthalpy of solution of NaCl is$ (1) $+ 572 kJ mol^{- 1}$ (2) $+ 4 kJ mol^{- 1}$ (3) $- 572 kJ mol^{- 1}$ (4) $- 4 kJ mol^{- 1}$ 213. $The first law of thermodynamics for isothermal process is$ (1) $q = - W$ (2) $Δ U = W$ (3) $Δ U = q$ (4) $Δ U = - q_{v}$ 214. $If the standard enthalpy change (Δ_{r} H^{\circ}) for a certain reaction at 298 K and constant pressure is - 1860 kJ mol^{- 1}, the standard entropy change (Δ_{sys} S^{\circ}) of the same reaction is - 550 J K^{- 1} mol^{- 1}, which one of the following statements is correct?$ (1) $Δsys S\circ+Δsurr S\circ=-7692 J mol^{- 1} K-1, the reaction is spontaneous$ (2) $Δsys S\circ+Δsurr S\circ=-5692 J mol^{- 1} K-1, the rcaction is non-spontaneous$ (3) $Δsys S\circ+Δsurr S\circ=+5692 J mol^{- 1} K-1, the reaction is spontaneous$ (4) $Δsys S\circ+Δsurr S\circ=+7692 J mol^{- 1} K-1, the reaction is non-spontaneous$ 215. $If the bond energies of HH, Br - Br, and HBr are 433, 192 and 364 kJmo l^{- 1} respectively, the Δ H^{o} for the reaction H_{2 (g)} + B r_{2 (g)} \to 2 HB r_{(g)} is$ (1) $- 261 kJ$ (2) $+ 103 kJ$ (3) $+ 261 kJ$ (4) $- 103 kJ$ 216. $A gas is allowed to expand in a well-insulated container against a constant external pressure of 2.5 atm from an initial volume of 2.50 L to a final volume of4.50 L. The change in internal energy Δ U of the gas in joules will be$ (1) $- 500 J$ (2) $- 505 J$ (3) $+ 505 J$ (4) $1136.25 J$ 217. $A chemical reaction is catalyzed by a catalyst X. Hence X$ (1) $reduces enthalpy of the reaction$ (2) $does not affect equilibrium constant of reaction$ (3) $decreases rate constant of the reaction$ (4) $increases activation energy of the reaction.$ 218. $One mole of an ideal gas at 300 K is expanded isothermally from an initial volume of 1 litre to 10litres. The Δ E for this process is (R = 2 cal mo 1^{- 1} K^{- 1})$ (1) $1381.1 cal$ (2) $zero$ (3) $163.7 cal$ (4) $9 L atm$ 219. $Which of the following p - V curve represents maximum work done?$ (1) (2) (3) (4) 220. $Given : C(graphite) + O2(g) \to CO2(g) ; ΔrHº = - 393.5 kJ mol-1 ; H2(g) + \frac{1}{2} O2(g) \to H2O(l) ; ΔrHº = - 285.8 kJ mol-1 ; CO2(g) + 2H2O(l) \to CH4(g) + 2 O_{2} (g) ; ΔrHº = + 890.3 kJ mol-1 Based on the above thermochemical equations, the value of ΔrHº at 298 K for the reaction : C(graphite) + 2H2(g) \to CH4(g) will be :$ (1) $+144.0 kJ m o l^{-1}$ (2) $-74.8 kJ m o l^{-1}$ (3) $-144.0 kJ m o l^{-1}$ (4) $+74.8 kJ m o l^{-1}$ 221. $0.06 mole of KNO_{3} solid is added to 100 cm^{3} of water at 298 K . The enthalpy of KNO_{3 (aq)} solution is 35.8 kJ mol^{- 1} . After the solute is dissolved the temperature of the solutions will be$ (1) $293 K$ (2) $298 K$ (3) $301 K$ (4) $304 K .$ 222. $If enthalpies of formation for C_{2} H_{4 (g)}, C O_{2 (g)} and H_{2} O_{(l)} at 2 5^{o} C and 1 atm pressure are 52, - 394 and - 286 kJ/mol respectively, then enthalpy of combustion of C 2 H_{4 (g)} will be$ (1) $+ 141.2 kJ/mol$ (2) $+ 1412 kJ/mol$ (3) $- 141.2 kJ/mol$ (4) $- 1412 kJ/mol$ 223. $A process has DH = 200 J m o l^{-1} and DS = 40 J K^{-1} m o l^{-1} . Out of the values given below, choose the minimum temperature above which the process will be spontaneous$ (1) $5 K$ (2) $12 K$ (3) $4 K$ (4) $20 K$ 224. $Identify the correct statements from the following. (i) For adiabatic process, Δ U = W_{adiabatic} (ii) Work is a path function. (iii) Volume is an extensive property.$ (1) $i, ii, iii$ (2) $i, iii only$ (3) $ii, iii only$ (4) $i, ii only$ 225. $The entropy change, in the conversion of one mole of liquid water at 373 K to vapour at the same temperature is (Latent heat of vaporization of water, Δ H_{vap} = 2.257 kJ / g)$ (1) $105.9 Jk^{- 1}$ (2) $107.9 Jk^{- 1}$ (3) $108.9 Jk^{- 1}$ (4) $109.9 Jk^{- 1}$ 226. $For the thermochemical equation, 2 H_{2 (g)} + O_{2 (g)} \to 2 H_{2} O_{(t)}; H = - 571.6 kJ Heat of decomposition of water is$ (1) $- 571.6 kJ$ (2) $+ 571.6 kJ$ (3) $- 1143.2 kJ$ (4) $+ 285.8 kJ$ 227. $The densities of graphite and diamond at298 K are 2.25 and 3.31 gc m^{- 3}, respectively. If the standard fr ee energy difference (G) is equal to 1895 Jmo l^{- 1}, the pressure at which graphite will be transformed into diamond at 298 K is$ (1) $9.92 \times 1 0^{8} Pa$ (2) $9.92 \times 1 0^{7} Pa$ (3) $9.92 \times 1 0^{6} Pa$ (4) $None of these$ 228. $For the reaction, C 2 H_{5} O H_{(l)} + 3 O_{2 (g)} \to 2 C O_{2 (g)} + 3 H_{2} O_{(l)} which one is true?$ (1) $Δ H = Δ E - RT$ (2) $Δ H = Δ E + RT$ (3) $Δ H = Δ E + 2 RT$ (4) $Δ H = Δ E - 2 RT$ 229. $During winters, moisture condenses in the form of dew and can be seen on plant leaves and grass. The entropy of the system in such cases decreases as liquids possess lesser disorder as compared to gases. With reference to the second law, which statement is correct, for the above process?$ (1) $The randomness of the universe decreases$ (2) $The randomness of the surroundings decreases$ (3) $Increase is randomness of surroundings equals to the decrease in randomness of system$ (4) $The increase in randomness of the surroundings is greater as compared to the decrease in randomness of the system.$ 230. $During which of the following processes, does entropy decrease? (A) Freezing of water to ice at 0^{\circ} C (B) Freezing of water to ice at - 10^{\circ} C (C) N_{2} (g) + 3 H_{2} (g) \to 2 NH_{3} (g) (D) Adsorption of CO (g) and lead surface(E) Dissolution of NaCl in water$ (1) $(A),(B),(C)and (D) only$ (2) $(B) and (C) only$ (3) $(A) and (E) only$ (4) $(A), (C) and (E) only$ 231. $Calculate Δ H for following reaction, at 25^{\circ} C . NH_{2} CN_{(g)} + \frac{3}{2} O_{2 (g)} ⟶ N_{2 (g)} + CO_{2 (g)} + H_{2} O_{(l)} (Δ U = - 740.5 kJ, R = 8.314 J K^{- 1} mol^{- 1})$ (1) $- 708.4 kJ mol^{- 1}$ (2) $- 789.3 kJ mol^{- 1}$ (3) $- 741.7 kJ mol^{- 1}$ (4) $- 863.9 kJ mol^{- 1}$ 232. $If the work done by 2 mol of an ideal gas during isothermal reversible expansion from 5 L to 50 L is - 189.1 L atm at constant pressure, the temperature of the gas (in^{\circ} C) is$ (1) $500$ (2) $227$ (3) $327$ (4) $127$ 233. $The entropy change associated with the conversion of 1 kg of ice at 273 K to water vapours at 383 K is: (Specific heat of water liquid and water vapour are 4.2 kJ K^{-1} k g^{-1} and 2.0 kJ K^{-1} k g^{-1}; heat of liquid fusion and vapourisation of water are 334 kJ k g^{-1} and 2491 kJ k g^{-1}, respectively). (log 273 = 2.436, log 373 = 2.572, log 383 = 2.583)$ (1) $8.49 kJ k g^{-1} K^{-1}$ (2) $9.26 kJ k g^{-1} K^{-1}$ (3) $2.64 kJ k g^{-1} K^{-1}$ (4) $7.90 kJ k g^{-1} K^{-1}$ 234. $Identify the pair in which both are not extensive properties -$ (1) $Internal energy, enthalpy$ (2) $Mass, volume$ (3) $Density, pressure$ (4) $Heat capacity Gibbs energy$ 235. $For a reaction 2 CO (g) + O_{2} (g) ⇌ 2 CO_{2} (g), Δ_{I} G^{0} = - 128 kJ at 300 K . If Δ_{r} S^{0} of the reaction is - 40 J K^{- 1}, calculate Δ_{r} U of the reaction.$ (1) $- 137.5 kJ$ (2) $- 128 kJ$ (3) $- 140 kJ$ (4) $126.2 kJ$ 236. $The bond dissociation energies of X_{2}, Y_{2} and XY are in the ratio of 1: 0.5: 1. Δ H for the formation of XY is - 200 kJmo l^{- 1} . The bond dissociation energy of X_{2} will be$ (1) $200 kJmo l^{- 1}$ (2) $100 kJmo l^{- 1}$ (3) $800 kJmo l^{- 1}$ (4) $400 kJmo l^{- 1}$ 237. $For the reaction, 2 Cl (g) \to Cl_{2} (g), the correct option is:$ (1) $Δ_{r} H > 0 and Δ_{r} S < 0$ (2) $Δ_{r} H < 0 and Δ_{r} S > 0$ (3) $Δ_{r} H < 0 and Δ_{r} S < 0$ (4) $Δ_{r} H > 0 and Δ_{r} S > 0$ 238. $Standard enthalpy of vapourisation for CCl_{4} is 30.5 kJ mol^{- 1} . Heat required for vapourisation of 284 g of CCl_{4} at constant temperature is________kJ . (Given molar mass in gmol^{- 1}; C = 12, Cl = 35.5)$ 239. $When a 60 W electric heater is immersed in a gas for 100 s in a constant volume container with adiabatic walls, the temperature of the gas rises by 5 ° C. The heat capacity of the given gas is J K^{- 1} (Nearest integer)$ 240. $Consider the two different first order reactions given below A + B \to C (Reaction 1) P \to Q (Reaction 2) The ratio of the half life of Reaction 1 : Reaction 2 is 5 : 2 . If t_{1} and t_{2} represent the time taken to complete 2/ 3^{r d} and 4/ 5^{t h} of Reaction 1 and Reaction 2, respectively, then the value of the ratio t_{1} : t_{2} is ____\times 1 0^{- 1} (nearest integer). [Given : lo g_{10} (3) = 0.477 and lo g_{10} (5) = 0.699]$