Monday_solution[1]

Monday_solution[1] - 1 2 nd Midterm Exam(Solutions to...

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Unformatted text preview: 1 2 nd Midterm Exam (Solutions to worked problems) ‐ 2009.03.16 1) Ammonium nitrate can decompose explosively when heated according to the following equation: 2NH 4 NO 3 (s) Æ 2N 2 (g) + 4H 2 O (g) + H 2 (g) How many litres of gas total would be formed at 450 o C and 4.56 bar pressure by the explosion of 450g of NH 4 NO 3 ? Assuming ideal gas behaviour Î PV = nRT P = 4.56 bar /1.01325 (bar/atm) = 4.5 atm T = 450 + 273 = 723 K Vgas = (nN 2 +nH 2 O+nH 2 ) x 0.0821 (atm.L/K.mol) x 723 K /4.5 atm (nN 2 +nH 2 O+nH 2 ) = (7/2) x n(NH 4 NO 3 ) = (7/2) x [450 g/ 80 (g/mol)] = 19.68 mole of gas total where 80 g/mol = molar mass of NH 4 NO 3 V = 258.4 L 2) Calculate the enthalpy of combustion per mole for C 6 H 12 O 6 . Assume that the combustion products are CO 2 (g) and H 2 O(l). Species Δ H° f (kJ/mol ) H 2 O(l) ‐ 285.8 C 6 H 12 O 6 (s) ‐ 1260 CO 2 (g) ‐ 393.5 Combustion reaction: C 6 H 12 O 6 (s) + 6 O 2 (g) Î 6 CO 2 (g) + 6 H 2 O(l) Δ H o f (O 2 , g) = 0 Δ H o rxn = [6 ( ‐ 393.5)+6 (393....
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Monday_solution[1] - 1 2 nd Midterm Exam(Solutions to...

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