Title DPP-2 SOLUTION.pdf ✅

CLASS : XIth SUBJECT : CHEMISTRY DATE : DPP No. : 2 1 (c) Heat of formation of H2O = ― heat of decomposition of water. 2 (a) Tfirreversible > Tfreversible it is an adiabatic expansion and W(rev) is maximum. 3 (c) Molecular solids are covalent compounds having low m.p. 4 (a) ∆H = H P ― H R Thus, ∆H is negative because H P < H R. 5 (b) ∆G = ― ve for a spontaneous change. 6 (d) Ideal gas does not show intermolecular forces of attractions. 7 (b) Rest all are correct . 8 (a) During solidification disorder decreases. 9 (a) ∆S = ∆Hf T = 2930 300 = 9.77 J mol―1K ―1 10 (d) ∆G = ∆H ― T∆S The reaction will be spontaneous If T∆S > ∆H (i.e.,∆G = ―ve) T > ∆H ∆S = 170 170 × 10―3 = 1000 K 11 (c) θ is independent of initial amount as long as relative amount is constant 12 (b) q = ∆U ― W, if adiabatic process q = 0, then ―∆U = ―W, i.e., a decrease in free energy brings in work done by the system ( ― W). Topic :- THERMODYNAMICS Solutions
13 (a) As the system is closed and insulated, no heat enter or leave the system, ie, q = 0 ∴ ∆E = q + W = W 14 (b) XY→X(g) +Y(g); ∆H = +a kJ/mol ...(i) X2→2X; ∆H = +a kJ/mol ...(ii) Y2→2Y; ∆H = +0.5a kJ/mol ...(iii) 1 2 × (ii) + 1 2 × (iii) ― (i) gives 1 2 X2 + 1 2 Y2→XY ∆H = ( + a 2 + 0.5 2 a ― a)kJ/mol ∴ ― 200 = + a 2 + 0.5a 2 ― a or a = 800 15 (d) CH4 →C + 4H; ∆H = 360 kcal/mol eC─H = 90 kcal C2H6 →2C + 6H; ∆H = 620 kcal/mol ∴ 620 = eC─C + 6eC─H ∴ eC─C = 620 ― 540 = 80 kcal/mol 16 (d) Molecular weight of NH4NO3 = 80 ∴ Molar heat of decomposition H = ms∆t = 80 + 1.23 × 6.12 = 602 kJ/mol 17 (b) Greater is bond energy more is stability to bond. 18 (a) Due to high bond energy of N ≡ N, more heat is absorbed to break up N2 molecule. 19 (a) ∆Svap = (900 × 18) 373 = 43.4 JK ―1mol ―1 20 (b) For spontaneous reaction ∆G = ― ve. ∆G = ∆H ― T∆S ∆H = + ve,∆S = + ve and T∆S > ∆H
ANSWER-KEY Q. 1 2 3 4 5 6 7 8 9 10 A. C A C A B D B A A D Q. 11 12 13 14 15 16 17 18 19 20 A. C B A B D D B A A B