Exercises 1.1 The enthalpy changes for the following reactions are as follows: 2B + 3H2 + 302 + aq. = + 2H ZBO3(dil.sol); AHO 298 -512.8 kcal(-2, 146.6 kJ). B2O3 + 3H2O(l) + aq. + + 24.3B03(dil.sol ) AHO -4.12 kcal (-77, 24 kJ). 298 H + 102 H2O(l); . -68.73 kcal (-287.57 W). 298 Calculate the standard heat of formation of Bzz in terms of per mole of B203 and per 9 of B2O3. Atomic weights of B and O are 10.82 and 16.0 respectively. 1.3 Fez z, PbO and Cugo present in a dead roasted tin ore react according to the following equations, during leaching with 1.11 M HC1 (= HCI(50 H20)) at 25C (298 k) Fe2O3 + 6HC1(50 H20) 2FeC 13(150 H20) + 3H20, PbO + 2HC1(50 H20) = ci (100 0) + H20, Cu2O + 2HC1( 50 H20) 2Cuci(50 H20) + H20. Calculate the heat of the leaching process at 25C (298 K) per 100 kg of ore, assuming that the SiO2 and sno, present in the ore are unaffected during leaching. Given: (i) Composition of dead roasted tin ore is 10% Fe2O3, 5% PbO, 5% Cuyo, 15% SiO2 and rest Snoz. (ii) Standard heats of formation of Fe2O3, Cuzo, PbO, FeCl3(150 H20), CuCl(50 H20), PbC12(100 H20), H2O, HC1(50 H2O) at 25c are -796.3, -40.0, -52.4, -92.0, -30.9, -83.2, -68.32 and -17.4 kcal/mole (-821.3, -167.4, -219.2, -384.9, -129.3, -348.1, - 285.8 and -72.8 kJ/moll respectively. 1.4 The reduction of iron oxide in the blast furnace proceeds according to the following reactions: 3Fe2O3 + CO = 2Fe3O4 + CO2; + 4 298 -12.7 kcal (-53.1 kJ). 3FeO + CO2; Fezn + Co , 298 +9.8 kcal (+ 41.0 kJ). FeO + CO Fe + CO2 AH -4.4 kcal (-18.4 kJ). 298 Calculate H 298 for the reaction Fe2O3 + 300 2Fe + 3002: 1.5 Calculate the heat of reaction of the Hall-Heroult process, viz. Al2O3 + 3C = 300 + 2A1 at 25C (298 K) from the following data: 2A1 + A1203; -7,400 cal (-30,962 J) per g of Al reacted. 440 298 C + 202 CO; AHO 298 -2,250 cal (-9,414 J) per g of C reacted. Atomic weights of A1 and C are 27 and 12 respectively