Thermodynamics PYQs Set 15 (PDF)

Set 15 of 18 · Questions 421-450 of 511

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Mere Teacher · Previous Year Questions JEE Main Chemistry · Thermodynamics · Set 15 (Q421-450)
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421. $When reaction in standard state is at equilibrium, then:$ (1) $DHº = 0$ (2) $DSº = 0$ (3) $equilibrium constant K = 0$ (4) $equilibrium constant K = 1$ 422. $The standard state Gibbs free energies of formation of C(graphite) and C(diamond) at T = 298 K are Δ_{f} Gº[C(graphite)] = 0 kJ m o l^{-1} Δ_{f} Gº[C(diamond)] = 2.9 kJ m o l^{-1} The standard state means that the pressure should be 1 bar, and substance should be pure at a given temperature. The conversion of graphite [C(graphite)] to diamond [C(diamond)] reduces its volume by 2 \times 1 0^{-6} m^{3} m o l^{-1} . If C(graphite) is converted to C(diamond) isothermally at T = 298 K, the pressure at which C(graphite) is in equilibrium with C(diamond), is : [Useful information: 1 J = 1 kg m^{2} s^{-2}, 1 Pa = 1 kg m^{-1} s^{-2}; 1 bar = 1 0^{5} Pa]$ (1) $58001 bar$ (2) $1450 bar$ (3) $14501 bar$ (4) $29001 bar$ 423. $What will be the melting point of KCl if enthalpy change for the reaction is 7.25 J m o l^{- 1} and entropy change is 0.007 J K^{- 1} m o l^{- 1} ?$ (1) $1835.2 K$ (2) $173 K$ (3) $1035.7 K$ (4) $1285.2 K$ 424. $Mixing of non-reacting gases is generally accompanied by (non-reacting)$ (1) $Decrease in entropy$ (2) $Increase in entropy$ (3) $Change in enthalpy$ (4) $Change in free energy$ 425. $The true statement amongst the following is:$ (1) $Both S and AS are not functions of temperature.$ (2) $S is not a function of temperature but AS is a function of temperature.$ (3) $Both AS and S are functions of temperature.$ (4) $S is a function of temperature but AS is not a function of temperature.$ 426. $For a spontaneous reaction the ∆ G, equilibrium constant (K) and E_{ce l l}^{0} will be respectively$ (1) $- ve, > 1, + ve$ (2) $+ ve, > 1, - ve$ (3) $- ve, < 1, -ve$ (4) $- ve, > 1, - ve$ 427. $Consider the following liquid‐vapour equilibrium. Liquid - Vapour Which of the following relations is correct?$ (1) $\frac{d ln P}{d T ^{2}} = \frac{- Δ H _{v}}{T ^{2}}$ (2) $\frac{d ln P}{dT} = \frac{Δ H _{v}}{R T ^{2}}$ (3) $\frac{d ln G}{d T ^{2}} = \frac{Δ H _{v}}{R T ^{2}}$ (4) $\frac{d ln P}{dT} = \frac{- Δ H _{v}}{RT}$ 428. $When disorder of a system increases, the change is said to be$ (1) $Exothermic$ (2) $Non-spontaneous$ (3) $Endothermic$ (4) $Spontaneous$ 429. $For a particular reaction DH° = - 76.6 KJ and DS° = 226 J K^{-1} . This reaction is:$ (1) $Spontaneous at all temperatures$ (2) $Non spontaneous at all temperatures$ (3) $Spontaneous at temperature below 66°C$ (4) $Spontaneous at temperature above 66°C$ 430. $For the reaction N_{2} + 3 H_{2} ⇋ 2 N H_{3}, Δ H = ?$ (1) $Δ E + 2 RT$ (2) $ΔE-2RT$ (3) $Δ H = RT$ (4) $Δ E - RT$ 431. $The entropy of crystalline substances at absolute zero going by the third law of thermodynamics should be taken as$ (1) $100$ (2) $50$ (3) $Zero$ (4) $Different for different substances$ 432. $In which of the following reaction Δ_{r} Sº > 0$ (1) $SO2 (g) + \frac{1}{2} O2 (g) \to SO3 (g)$ (2) $2O3 (g) \to 3O2 (g)$ (3) $NaCl (s) \toNaCl (aq)$ (4) $H2 (g) \to 2H (g)$ 433. $A reaction having equal energies of activation for forward and reverse reactions has$ (1) $Δ H = 0$ (2) $Δ H = Δ G = Δ S = 0$ (3) $Δ S = 0$ (4) $Δ G = 0$ 434. $Identify false statement regarding isothermal process from following.$ (1) $System can exchange heat energy with the surrounding.$ (2) $Enthalpy of system remains constant.$ (3) $Temperature of systems remains constant.$ (4) $Internal energy of system remains constant.$ 435. $Mixing of non-reacting ideal gases is generally accompanied by$ (1) $Decrease in entropy$ (2) $Increase in entropy$ (3) $Change in enthalpy$ (4) $Increase in free energy$ 436. $At 27Clatent heat of fusion of a compound is 2930 J / mol . Entropy change is$ (1) $9.77 J/mol‐K$ (2) $10.77 J/mol‐K$ (3) $9.07 J/mol‐K$ (4) $0.977 J/mol‐K$ 437. $A sample of liquid in a thermally insulated container (a calorimeter) is stirred for 2 hr. by a mechanical linkage to a motor in the surrounding, for this process :$ (1) $w< 0; q = 0; Δ U = 0$ (2) $w > 0; q > 0; Δ > 0$ (3) $w< 0; q > 0; ∆ = 0$ (4) $w > 0; q = 0; Δ > 0$ 438. $Which amongst the following options is the correct relation between change in enthalpy and change in internal Energy?$ (1) $Δ H + Δ U = Δ nR$ (2) $Δ H = Δ U - Δ n_{g} RT$ (3) $Δ H = Δ U + Δ n_{g} RT$ (4) $Δ H - Δ U = - Δ nRT$ 439. $Identify the reaction/process in which the entropy increases.$ (1) $H (g) + H (g) \to H_{2} (g)$ (2) $H_{2} O (g) \to H_{2} O (s)$ (3) $H_{2} O (1) \to H_{2} O (g)$ (4) $A (g) + B (g) + C (s) \to 2 D (s)$ 440. $Which of the reaction defines molar Δ H_{f}^{\circ} ?$ (1) $CaO (s) + C O_{2} (g) \to CaC O_{3} (s)$ (2) $\frac{1}{2} B r_{2} (ℓ) + \frac{1}{2} H_{2} (g) \to HBr (g)$ (3) $N_{2} (g) + 2 H_{2} (g) + \frac{3}{2} O_{2} (g) \to N H_{4} N O_{3} (s)$ (4) $\frac{1}{2} I_{2} (s) + \frac{1}{2} H_{2} (g) \to HI (g)$ 441. $Five moles of an ideal gas at 1 bar and 298K is expanded into vacuum to double the volume. The work done is :$ (1) $Zero$ (2) $- RT ln V_{2} / V_{1}$ (3) $C_{v} (T_{2} - T_{1})$ (4) $- RT (V_{2} - V_{1})$ 442. $When liquid solidifies, generally there is :$ (1) $Decrease in enthalpy$ (2) $Decrease in entropy$ (3) $Increase in enthalpy$ (4) $Increase in entrapy$ 443. $Mixing of non-reacting gases is generally accompanied by$ (1) $Decrease in entropy$ (2) $Increase in entropy$ (3) $Change in enthalpy$ (4) $Change in free energy$ 444. $The standard reaction Gibbs energuy for a chemical reaction at an absolute temperature T is given by DG° = A - BT, where A and B are non-zero constants. Which of the following is TRUE about this reaction ?$ (1) $Endothermic if A > 0$ (2) $Exothermic if B < 0$ (3) $Exothermic if A > 0 and B < 0$ (4) $Endothermic if A < 0 and B > 0$ 445. $The Born-Haber cycle for is evaluated with the following data : Δ_{f} H^{⊖} KCl = - 436.7 kJ m o l^{- 1}; Δ_{s u b} H^{⊖} for K = 89.2 kJ m o l^{- 1}; Δ_{i o ni z a t i o n} H^{⊖} for K = 419.0 kJ m o l^{- 1}; Δ_{e l ec t r o n g ain} H^{⊖} for C l_{(g)} = - 348.6 kJ m o l^{- 1}; Δ_{l o n d} H^{0} for C l_{2} = 243.0 kJ m o l^{- 1} . The magnitude of lattice enthalpy of KCl in kJ m o l^{- 1} is ____. (Nearest integer)$ 446. $Given: Δ H^{⊖}_{sub} [C(graphite)] = 710 kJ mol^{- 1} Δ_{C - H} H^{⊖} = 414 kJ mol^{- 1} Δ_{H - H} H^{⊖} = 436 kJ mol^{- 1} Δ_{C} = CH^{⊖} = 611 kJ mol^{- 1} The Δ H_{f} ⊖ for CH_{2} = CH_{2} is kJmol^{- 1} (nearest integer value)$ 447. $The enthalpy of combustion of propane, graphite and dihydrogen at 298 K are: -2220.0 kj m o l^{- 1}, -393.5 kJ m o l^{- 1} and -285.8 kJ m o l^{- 1} respectively. The magnitude enthalpy of formation of propane (C_{3} H_{8}) is.........kJ m o l^{- 1} . (Nearest integer)$ 448. $The formation enthalpies, Δ H_{f} ⊖ for H_{(g)} and O_{(g)} are 220.0 and 250.0 kJ mol^{- 1}, respectively, at 298.15 K , and Δ H_{f}^{⊖} for H_{2} O_{(g)} is - 242.0 kJ mol^{- 1} at the same temperature. The average bond enthalpy of the O - H bond in water at 298.15 K is kJmol^{- 1} (nearest integer).$ 449. $17.0 g of N H_{3} completely vapourises at - 33.42°C and 1 bar pressure and the enthalpy change in the process is 23.4 kJ m o l^{- 1} . The enthalpy change for the vapourisation of 85 g of N H_{3} under the same conditions is________kJ.$ 450. $Among the following the number of state variable is______. Internal energy (U) Volume (V) Heat (q) Enthalpy (H)$