Order Homogeneous and heterogeneous systems

Order Homogeneous and heterogeneous systems
66. In a reversible Carnot cycle, W = 150 kJ; Q(supplied) at T1
= 225 kJ . Calculate (i) efficiency and (ii) the lower temperature, T2
K . (T1
= 227qC)
(a) 0.5; 150 (b) 0.75; 170 (c) 0.75 ; 180 (d) 0.67 ; 299
67. An ideal gas at 3 atm pressure and 300K is expanded isothermally and reversibly to double its initial volume. Calculate
in cal K1
the entropy change for 10 moles of the gas
(a) 17.37 (b) 11.73 (c) 13.77 (d) 17.11
68. For the reaction 2Cl(g)oCl2(g), What are the signs of ‘H and ‘S?
(a) Both ‘H and ‘S are positive (b) ‘H negative, ‘S positive
(c) ‘H positive, ‘S negative (d) ‘H negative, ‘S negative
69. Which of the following changes has the sign of ‘S ( ve or ve) opposite to that of the other three?
(a) C(graphite)oC(diamond) (b) Br2(l)oBr2(g)
(c) N2(g, 10 atm)oN2(g, 1 atm) (d) C(s) H2
O(g)oCO(g) H2(g)
70. Two moles of CO2(g) at a pressure of 5 atm and 25qC are heated to 125qC and compressed to 25 atm. Cp
= 37.1 J K1
mol1
(assumed to be independent of temperature). Calculate ‘S
(a) 5.03 J K1
(b) 5.30 J K1
(c) 3.50 J K1 (d) 3.50 J K1
71. Which of the following processes is accompanied by a decrease in entropy?
(a) Isothermal compression of an ideal gas
(b) A liquid heated from 298K to its boiling point at constant pressure
(c) Urea dissolved in water
(d) The fusion of a solid at atmospheric pressure
Order Homogeneous and heterogeneous systems
72. Indicate among the following the correct statement.
(a) The feasibility of a reaction is determined by the magnitude of the entropy.
(b) At 0qC the entropy of a perfectly crystalline substance is taken to be zero.
(c) For a reversible adiabatic volume change of an ideal gas pVJ
= constant for one mole.
(d) n-Hexane and 2,2-dimethyl butane have exactly the same magnitude of ‘Hf.
5.44 Chemical Energetics and Thermodynamics
that the forward reaction becomes spontaneous above 2000K
76. For the reaction; 2A(g) 3B(g)o2C(g), ‘Uq300K = 5 k cal, ‘Sq300K = 20 cal K1
. Predict the feasibility of the reaction
by calculating ‘Gq
(a) 700 cal; not feasible (b) 800 cal ; feasible
(c) 650 cal ; feasible (d) 650 cal ; not feasible
77. Calculate the phase-transition temperature for Sn(grey) Sn(white) .
at 2025qC for the conversion N2(g) O2(g) 2NO(g). If N2(g) and O2(g) are to be passed into a reaction
chamber at 50 atm for each and NO gas is to be withdrawn at 30 atm from the chamber; What is ‘G for the process?
Is the process feasible?
(a) 153.0 kJ ; not feasible (b) 153.0 kJ ; feasible (c) 130.5 kJ ; not feasible (d) 103.5 kJ ; not feasible
80. The temperature coefficient of the free energy change of a reaction at constant pressure i.e.,
.