Problem 112
Determine \(\Delta \mathrm{H}\) and \(\Delta \mathrm{E}\) for reversible isothermal evaporation of \(90 \mathrm{~g}\) of water at \(100^{\circ} \mathrm{C}\). Assume that water vapour behaves as an ideal gas and heat of evaporation of water is \(540 \mathrm{cal} \mathrm{g}^{-1}\left(\mathrm{R}=2.0 \mathrm{cal} \mathrm{mol}^{-1} \mathrm{~K}^{-1}\right)\) (a) \(48600 \mathrm{cal}, 44870 \mathrm{cal}\) (b) \(43670 \mathrm{cal}, 47700 \mathrm{cal}\) (c) 47700 cal, \(43670 \mathrm{cal}\) (d) \(44870 \mathrm{cal}, 48670 \mathrm{cal}\)
Problem 114
The standard heat of combustion of \(\mathrm{Al}\) is \(-837.8 \mathrm{~kJ}\) \(\mathrm{mol}^{-1}\) at \(25^{\circ} \mathrm{C}\). If \(\mathrm{Al}\) reacts with \(\mathrm{O}_{2}\) at \(25^{\circ} \mathrm{C}\), which of the following releases \(250 \mathrm{kcal}\) of heat? (a) the reaction of \(0.312 \mathrm{~mol}\) of \(\mathrm{Al}\) (b) the formation of \(0.624 \mathrm{~mol}\) of \(\mathrm{Al}_{2} \mathrm{O}_{3}\) (c) the reaction of \(0.712 \mathrm{~mol}\) of \(\mathrm{Al}\) (d) the formation of \(0.615 \mathrm{~mol}\) of \(\mathrm{A} 1 \mathrm{O}_{3}\)
Problem 115
The dissociation energies of \(\mathrm{CH}_{4}\) and \(\mathrm{C}_{2} \mathrm{H}_{6}\) to convert them into gaseous atoms are 360 and \(620 \mathrm{kcal}\) mol respectively. The bond energy of \(\mathrm{C}-\mathrm{C}\) bond is (a) \(280 \mathrm{kcal} \mathrm{mol}^{-1}\) (b) \(240 \mathrm{kcal} \mathrm{mol}^{-1}\) (c) \(160 \mathrm{kcal} \mathrm{mol}^{-1}\) (d) \(80 \mathrm{kcal} \mathrm{mol}^{-1}\)
Problem 116
Calculate \(\mathrm{Q}\) and \(\mathrm{W}\) for the isothermal reversible expansion of one mole of an ideal gas from an initial pressure of \(1.0\) bar to a final pressure of \(0.1\) bar at a constant temperature of \(273 \mathrm{~K}\). (a) \(5.22 \mathrm{~kJ},-5.22 \mathrm{~kJ}\) (b) \(-27.3 \mathrm{~kJ}, 27.3 \mathrm{~kJ}\) (c) \(27.3 \mathrm{~kJ},-27.3 \mathrm{~kJ}\) (d) \(-5.22 \mathrm{~kJ}, 5.22 \mathrm{~kJ}\)
Problem 117
Which of the following conditions may lead to a nonspontaneous change? (a) \(\Delta \mathrm{H}=-\mathrm{ve} ; \Delta \mathrm{S}=+\mathrm{ve}\) (b) \(\Delta \mathrm{H}=-\mathrm{ve} ; \Delta \mathrm{S}=-\mathrm{ve}\) (c) \(\Delta \mathrm{H}\) and \(\Delta \mathrm{S}\) are both \(+\mathrm{ve}\) (d) \(\Delta H=+v e ; \Delta S=-v e\)
Problem 119
Which of the following is /are true about the isothermal expansion of an ideal gas? (a) \(\Delta \mathrm{U}=0\) (b) \(\Delta \mathrm{T}=0\) (c) \(\mathrm{q}=2.303 \mathrm{nRT} \log _{10}\left(\frac{\mathrm{v}_{1}}{\mathrm{v}_{2}}\right)\) (d) \(\mathrm{q}=0\)
Problem 120
For which of the following reactions, is \(\Delta \mathrm{H}\) equal to \(\Delta \mathrm{E} ?\) (a) \(\mathrm{H}_{2}(\mathrm{~g})+\mathrm{I}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{HI}(\mathrm{g})\) (b) \(\mathrm{PCl}_{5}(\mathrm{~g}) \rightarrow \mathrm{PCl}_{3}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g})\) (c) \(2 \mathrm{H}_{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{~g})\) (d) \(\mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g})\)
Problem 121
For the system at equilibrium which of the following are correct? (a) On increasing the temperature of an endothermic reaction, the equilibrium shifts in forward direction because Q decreases. (b) On increasing the temperature of an endothermic reaction, the concentration in moles per litre of the reactants increases. (c) \(\log \mathrm{K}=\frac{1}{2.303 \mathrm{R}}\left(\Delta \mathrm{S}^{\circ}-\frac{\Delta \mathrm{H}^{\circ}}{\mathrm{T}}\right)\) (d) On increasing the temperature of an endothermic reaction, the equilibrium shifts in forward direction because \(\mathrm{K}\) increases.
Problem 122
Which are the intensive properties? (a) Volume (b) Enthalpy (c) Temperature (d) Refractive index
Problem 123
Which of the following relation is/are incorrect? (a) \(\Delta \mathrm{G}=\Delta \mathrm{H}+\Delta \mathrm{nRT}\) (b) \(\Delta \mathrm{G}=\Delta \mathrm{H}+\mathrm{T} \Delta \mathrm{S}\) (c) \(\Delta \mathrm{G}=\Delta \mathrm{H}+\mathrm{T}[\delta\\{\Delta \mathrm{G}\\} / \delta \mathrm{T}]_{\mathrm{P}}\) (d) \(\Delta \mathrm{G}=\Delta \mathrm{H}-\mathrm{T} \Delta \mathrm{S}\)
