Answer to Some Selected Problems UNIT 1 1.17 ~ 15 × 10–4 g , 1.25 × 10–4 m –3 5321.18 (i) 4.8 × 10(ii) 2.34 × 10(iii) 8.008 × 10(iv) 5.000 × 10(v) 6.0012 1.19 (i) 2 (ii) 3 (iii) 4 (iv) 3 (v)4 (vi)5 1.20 (i) 34.2 (ii) 10.4 (iii) 0.0460 (iv) 2810 1.21 (a) law of multiple proportion (b) (i) Ans : (106 mm, 1015 pm) (ii) Ans : (10–6 kg, 106 ng) (iii) Ans : (10–3 L, 10–3 dm3) –11.22 6.00 × 10 m =0.600 m 1.23 (i) B is limiting (ii) A is limiting (iii) Stoichiometric mixture –No (iv) B is limiting (v) A is limiting 1.24 (i) 2.43 × 103 g (ii) Yes (iii) Hydrogen will remain unreacted; 5.72 × 102g 1.26 Ten volumes –11 –11 –21.27 (i) 2.87 × 10m (ii) 1.515 × 10m (iii) 2.5365 × 10kg 1.30 1.99265 × 10–23g 1.31 (i) 3 (ii) 4 (iii) 4 1.32 39.948 g mol–1 1.33 (i) 3.131 × 1025 atoms (ii) 13 atoms (iii) 7.8286 × 1024 atoms 1.34 Empirical formula CH, molar mass 26.0 g mol–1, molecular formula C2H2 1.35 0.94 g CaCO3 1.36 8.40 g HCl UNIT 2 2.1 (i) 1.099 × 1027 electrons (ii) 5.48 × 10–7 kg, 9.65 × 104C 2.2 (i) 6.022 × 1024electrons (ii) (a) 2.4088 × 1021 neutrons(b) 4.0347 × 10–6 kg (iii) (a) 1.2044 × 1022 protons (b) 2.015 × 10–5 kg 2.3 7,6: 8,8: 12,12: 30,26: 50, 38 2.4 (i) Cl (ii) U (iii) Be 2.5 5.17 × 1014 s–1, 1.72 × 106m–1 2.6 (i) 1.988 × 10–18 J (ii) 3.98 × 10–15 J 2.7 6.0 × 10–2 m, 5.0 × 109 s–1 and 16.66 m–1 2.8 2.012 × 1016 photons –12.9 (i) 4.97 × 10–19 J (3.10 eV); (ii) 0.97 eV (iii) 5.84 × 105 m s2.10 494 kJ mol–1 2.11 7.18 × 1019s–1 2.12 4.41 × 1014s–1, 2.91 × 10–19J 2.13 486 nm 2.14 8.72 × 10–20J 2.15 15 emission lines 2.16 (i) 8.72 × 10–20J 2.17 1.523 × 106 m–1 2.18 2.08 × 10–11 ergs, 950 Å 2.19 3647Å 2.20 3.55 × 10–11m 2.21 8967Å (ii) 1.3225 nm 2.22 Na+, Mg2+, Ca2+; Ar, S2– and K+ 2.23 (i) (a) 1s2 (b) 1s2 2s2 2p6; (c) 1s22s22p6 (d) 1s22s22p6 2.24 n = 5 2.25 n = 3; l = 2; m = –2, –1, 0, +1, +2 (any one value)l2.26 (i) 29 protons 2.27 1, 2, 15 2.28 (i) l ml 00 1 –1,0,+1 2 –2,–1,0,+1,+2 (ii) l = 2; m=–2, –1,0,+1,+21(iii) 2s, 2p 2.29 (a) 1s, (b) 3p, (c) 4d and (d) 4f 2.30 (a), (c) and (e) are not possible 2.31 (a) 16 electrons (b) 2 electrons 2.33 n = 2 to n = 1 2.34 8.72 × 10–18J per atom 2.35 1.33 × 109 2.36 0.06 nm 2.37 (a) 1.3 × 102 pm (b) 6.15 × 107 pm 2.38 1560 2.39 8 2.40 More number of K–particles will pass as the nucleus of the lighter atoms is small, smaller number of K–particles will be deflected as a number of positve charges is less than on the lighter nuclei. 2.41 For a given element the number of prontons is the same for the isotopes, whereas the mass number can be different for the given atomic number. 81 2.42Br53 2.43 2.44 2.45 2.46 2.47 2.48 2.49 2.50 2.51 2.52 2.53 2.54 2.55 2.56 2.57 2.58 2.59 2.60 2.61 2.62 2.63 2.64 2.65 2.66 2.67 5.1 5.2 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12 5.13 37 Cl−1 17 56 3+Fe 26 Cosmic rays > X–rays > amber colour > microwave > FM 3.3 × 106 J –1(a) 4.87 × 1014 s(b) 9.0 × 109 m (c) 32.27 × 10–20 J (d) 6.2 × 1018 quanta 10 8.28 × 10–10 J 3.45 × 10–22 J (a) Threshold wave length (b) Threshold frequency of radiation 652.46 nm 4.598 ×1014 s–1 (c) Kinetic energy of ejected photoelectron –19.29 ×10–20 J, Velocity of photoelectron 4.516 × 105 ms530.9 nm 4.48 eV 7.6 × 103 eV infrared, 5 434 nm 455 pm 494.5 ms–1 332 pm 1.516 × 10–38 m Cannot be defined as the actual magnitude is smaller than uncertainity. (v) < (ii) = (iv) < (vi) = (iii) < (i) 4p (i) 2s (ii) 4d (iii) 3p Si (a) 3 (b) 2 (c) 6 (d) 4 (e) zero 16 UNIT 5 2.5 bar 0.8 bar 70 g/mol MB = 4MA 203.2 mL 8.314 × 104 Pa 1.8 bar 3g/dm3 1249.8 g mol–1 3/5 50 K 4.2154 × 1023 electrons 5.14 1.90956 × 106 year 5.15 56.025 bar 5.16 3811.1 kg 5.17 5.05 L 5.18 40 g mol–1 5.19 0.8 bar UNIT 6 6.1 (ii) 6.2 (iii) 6.3 (ii) 6.4 (iii) 6.5 (i) 6.6 (iv) 6.7 q = + 701 J w = – 394 J, since work is done by the system ΔU = 307 J 6.8 –743.939 kJ 6.9 1.067 kJ 6.10 ΔH = –7.151 kJ mol–1 6.11 – 314.8 kJ 6.12 Δ H = –778 kJ r 6.13 – 46.2 kJ mol–1 6.14 – 239 kJ mol–1 6.15 326 kJ mol–1 6.16 ΔS > 0 6.17 2000 K 6.18 Δ H is negative (bond energy is released) and ΔS is negative (There is less randomness among the molecules than among the atoms) 6.19 0.164 kJ, the reaction is not spontaneous. 6.20 –5.744 kJ mol–1 6.21 NO(g) is unstable, but NO6.22 qsurr = + 286 kJ mol–1 ΔS = 959.73 J K–1 surr 7.2 12.229 7.3 2.67 x 104 7.5 (i) 4.33 × 10–4 (ii) 1.90 7.6 1.59 × 10–15 2(g) is formed. UNIT 7 7.8 [N2] = 0.0482 molL–1, [O2] = 0.0933 molL–1, [N2O] = 6.6 × 10–21 molL–1 7.9 0.0352mol of NO and 0.0178mol of Br 2 7.10 7.47 × 1011 M–1 7.11 4.0 7.12 Qc = 2.379 × 103. No, reaction is not at equilibrium. 7.14 0.44 7.15 0.068 molL–1 each of H2 and I2 7.16 [I2] = [Cl2] = 0.167 M, [ICl] = 0.446 M 7.17 [C2H6]eq = 3.62 atm 7.18 (i) [CHCOOCH][HO] / [CHCOOH][CHOH]3252325(ii) 3.92 (iii) value of Q is less than K therefore equilibrium is not attained.cc7.19 0.02molL–1 for both. 7.20 [P] = 1.739atm, [P] = 0.461atm.CO CO27.21 No, the reaction proceeds to form more products. 7.22 3 × 10–4 molL–1 7.23 0.149 7.24 a) – 35.0kJ, b) 1.365 × 106 7.27 [P] = [P] = 2.5 × 10–2bar, [P] = 10.0 barH2 eq Br2 eqHBr7.30 b) 120.48 7.31 [H2]eq = 0.96 bar 7.33 2.86 × 10–28 M 7.34 5.85x10–2 –7.35 NO, HCN, ClO, HF, HO, HCO–, HS– 2 423 7.36 BF3, H+, NH4+ 7.37 F–, HSO4–, CO32– 7.38 NH , NH+, HCOOH34 7.41 2.42 7.42 1.7 x 10–4M 7.43 F–= 1.5 x 10–11, HCOO–= 5.6 × 10–11, CN–= 2.08 x 10–6 7.44 [phenolate ion]= 2.2 × 10–6, α = 4.47 × 10–5 , α in sodium phenolate = 10–8 7.45 [HS–]= 9.54 x 10–5, in 0.1M HCl [HS–] = 9.1 × 10–8M, [S2–] = 1.2 × 10–13M, in 0.1M HCl [S2–]= 1.09 × 10–19M 7.46 [Ac–]= 0.00093, pH= 3.03 7.47 [A –] = 7.08 x10–5M, Ka= 5.08 × 10–7, pKa= 6.29 7.48 a) 2.52 b) 11.70 c) 2.70 d) 11.30 7.49 a) 11.65 b) 12.21 c) 12.57 c) 1.87 7.50 pH = 1.88, pKa = 2.70 7.51 Kb = 1.6 × 10–6, pKb = 5.8 7.52 α = 6.53 × 10–4, Ka = 2.35 × 10–5 7.53 a) 0.0018 b) 0.00018 7.54 α = 0.0054 7.55 a) 1.48 × 10–7M, b) 0.063 c) 4.17 × 10–8M d) 3.98 × 10–7 7.56 a) 1.5 × 10–7M, b) 10–5M, c) 6.31 × 10–5M d) 6.31 × 10–3M 7.57 [K+] = [OH –] = 0.05M, [H+] = 2.0 × 10–13M 7.58 [Sr2+] = 0.1581M, [OH–] = 0.3162M , pH = 13.50 7.59 α = 1.63 × 10–2, pH = 3.09. In presence of 0.01M HCl, α = 1.32 × 10–3 7.60 Ka = 2.09 × 10–4 and degree of ionization = 0.0457 7.61 pH = 7.97. Degree of hydrolysis = 2.36 × 10–5 7.62 Kb = 1.5 × 10–9 7.63 NaCl, KBr solutions are neutral, NaCN, NaNO2 and KF solutions are basic and NH NO solution is acidic. 437.64 (a) pH of acid solution= 1.9 (b) pH of its salt solution= 7.9 7.65 pH = 6.78 7.66 a) 12.6 b) 7.00 c) 1.3 7.67 Silver chromate S= 0.65 × 10–4M; Molarity of Ag+ = 1.30 x 10–4M Molarity of CrO2– = 0.65 × 10–4M; Barium Chromate S = 1.1 × 10–5M; Molarity of4 Ba2+ and CrO42– each is 1.1 × 10–5M; Ferric Hydroxide S = 1.39 × 10–10M; Molarity of Fe3+ = 1.39 × 10–10M; Molarity of [OH–] = 4.17 × 10–10M Lead Chloride S = 1.59 × 10–2M; Molarity of Pb2+ = 1.59 × 10–2M Molarity of Cl– = 3.18 × 10–2M; Mercurous Iodide S = 2.24 × 10–10M; Molarity of Hg2+ = 2.24 × 10–10M and molarity of I– = 4.48 × 10–10M 2 7.68 Silver chromate is more soluble and the ratio of their molarities = 91.9 7.69 No precipitate 7.70 Silver benzoate is 3.317 times more soluble at lower pH 7.71 The highest molarity for the solution is 2.5 × 10–9M 7.72 2.43 litre of water 7.73 Precipitation will take place in cadmium chloride solution

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