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CHEMISTRY TODAY | APRIL ‘17 79
11. (a, d) : As, F 1 = k 1 x, F 2 = k 2 x. 1 2 1 2 Work done W1 = k1x and W2 = k2x 2 2 W1 k1 or α= = W2 k2 When the springs are stretched by the same force F, the extensions in springs A and B are x 1 and x 2 respectively which are given by F = k 1 x 1 = k 2 x 2 or x 1 k2 = …(i) x2 k1 1 2 1 2 Work done W1′= k1x1 and W2′ = k2x2 2 2 2 W1′ W ′ = k1 k ⋅ x1 …(ii) 2 2 2 x2 Using (i) and (ii) we get 2 W1′ β= W ′ = k1 k ⋅ k2 k = k2 2 2 2 k 1 1 800 − 80 12. (a, b, c, d) : Rate of heat flow H = ⎛ li ⎞ lo ⎝ ⎜ KA⎟ i ⎠ + ⎛ ⎞ ⎜ ⎝ KoA⎠ ⎟ which is also equal to 800 − T . Using these two ⎛ li ⎞ ⎝ ⎜ KA⎠ ⎟ i 720 relations we get, T = 800 − Ki lo + ⎛ . Thus ⎞ ⎛ ⎞ 1 ⎜ ⎝ Ko ⎠ ⎟ ⎜ ⎝ li ⎠ ⎟ one can reduce the temperature at the interface by any of the four options given. 13. (a, b, c, d) : Intensity, by definition, is the energy flowing per unit area per unit time. The intensity is related to the displacement amplitude A of the sound wave by 2 2 I = 1 ρω v A 2 The displacement amplitude is given by A = P , Bk ⎛ ω⎞ where k = ⎝ ⎜ v ⎠ ⎟ is the propagation constant. B The speed is given by v = . ρ 14. (2) : Use these relations to get the required expressions. A d/2 x B 2D Optic axis O x d/4 1 C 3f From similar triangles AOB and BDC OB AO = or x 1 d 2 = ( / ) BD CD x ( 2 d / 4) or x 1 = 2x 2 As x 1 + x 2 = 3f, 2x 2 + x 2 = 3f or x 2 = f i.e. x 1 = 2f n = 2. 15. (7) 16. (4) : Let the velocities of car 1 and car 2 be v 1 m s –1 and v 2 m s –1 . ∴ Apparent frequencies of sound emitted by car 1 and car 2 as detected at end point are υ0v υ0v υ1 = and υ − 2 = v v1 v − v2 300 × 330 −1 ∴ 330 = or v1 = 30 ms 330 − v1 300 × 330 −1 and 360 = or v2 = 55 ms 330 − v A 2 vt 1 vt 2 1 2 B 100 m The distance between both the cars just when the 2 n d car reaches point B(as shown in figure) is 100 m = v 2 t – v 1 t 100 100 t = = = 4 s v − v 55 − 30 2 1 17. (5) : The capacitance of a parallel plate capacitor in air is given by A C = ε 0 ...(i) d By introducing a slab of thickness t, the new capacitance C′ be<strong>com</strong>es ε C′ = 0 A ⎛ 1 ⎞ ...(ii) d′ −t⎜1 − ⎝ ⎠ ⎟ K The charge (Q = CV) remains the same in both the cases. Hence ε0A ε0A = d ⎛ 1 ⎞ d′ −t⎜1 − ⎝ K ⎠ ⎟ ⎛ 1 ⎞ or d= d′ −t − ⎝ ⎜1 K ⎠ ⎟ 80 CHEMISTRY TODAY | APRIL ‘17
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Volume 26 No. 4 April 2017 Managing
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(R) K[Co(NH ) (NO ) 4 ] 1. The volu
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24. m-Bromoaniline can be prepared
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(a) (b) (c) (d) CH CH C CH CH CH C
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20. (d) : CH 2 5 alk. KMnO 4 ( A) C
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41. (a) : According to Gibbs’-Hel
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5. Compound 'X' C 7 H 8 O, is insol
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(c) (d) O HC 2 O O HC 2 O O CH CH C
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4. As 2 S 3 sol carries a negative
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15. Cl CHONa + EtOH 2 5 Heat Possib
Page 23 and 24: (c) If θ = 10°, the charge underg
Page 25 and 26: (c) (d) NH 2 O heat NH HO 2 C CO 2
Page 27 and 28: (c) Dil. HCl followed by reaction w
Page 29 and 30: 33. Which of the following reaction
Page 31 and 32: Balz-Schiemann reaction : tetrauoro
Page 33 and 34: 26. (c) : HC 3 HC 3 -H O CH 2 3 H +
Page 35 and 36: 12. At equimolar concentration of F
Page 37 and 38: (a) 1s 2 , 2s 2 2p 6 , 3s 2 3p 6 3d
Page 39 and 40: Fraction of M present as M 2+ = 88
Page 41: 26. (b) : According to Gay-Lussac
Page 47 and 48: CONCEPT MAP PERIODICITY IN PROPERTI
Page 49 and 50: Class XII This specially designed c
Page 51 and 52: JEE MAIN / JEE ADVANCED / PETs Only
Page 53 and 54: CHEMISTRY MUSING SOLUTION SET 44 24
Page 55 and 56: Isothermal reversible expansion :
Page 57 and 58: (a) H 2 O/H + , BH 3·THF/H 2 O 2·
Page 59 and 60: 22. H 2 can be obtained from 28. Th
Page 61 and 62: 7. Predict the product for the foll
Page 63 and 64: 7. (d) : Cyclopropane is under seve
Page 65 and 66: 46. If the first and the (2n - 1) t
Page 67 and 68: 1 (a) 6 2 ms − (b) 4 2 (c) 7 m s
Page 69 and 70: tension, viscous force, weight but
Page 71 and 72: (a) HN 2 SO 3 H (b) (NH 2 ) 2 CO (c
Page 73: SOLUTIONS PAPER-I 1. (a) : The phot
Page 77 and 78: Given that, at equilibrium, ⎛ n
Page 79 and 80: 2 ∫ 53. (3) : (| x− 2| + [ x])
Page 81 and 82: percentage change in v = 1 2 perce
Page 83 and 84: Again, c 2 a 2 b 2 = + + 2a⋅b
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