MacBook Air 40) 4) F12 F11 F10 F9 FB F7 F5 sk delete 13. Consider the following

Question

MacBook Air 40) 4) F12 F11 F10 F9 FB F7 F5 sk delete 13. Consider the following thermochemical equation: 2 Fe (s) + 3/2 O2 (g) Fe2O3 (s); 11x,--840 kJ/mol Fe2O3 (s) formed If 0.100 mol Fe reacts, how much heat is liberated? A) 42.0 kJ B) 84.0 kJ C) 210 kJ D) 420 kJ E) 840 kJ 14. A 5.6 g sample of white phosphorus, P4 MW = 123.88 g/mol) was burned in a bomb calorimeter. The heat capacity of the calorimeter was 365 J/°C. If the resulting temperature change was 2.89°C, what is the molar heat of combustion for phosphorus in Jmole? A)2.28 B) -2.28 C) -1055 D) 1055 E) -23335

Explanation / Answer

Q13

the reaction is based on:

2 mol of Fe(s) --> -840 kJ released

1 mol of Fe(s) -840/(2) = -420 kJ released

0.1 mol of Fe --> 420*0.1 = 42 kJ will be realeases

choose A, 42 kJ

Q14

Qrxn = Ccal * DT = (365)(2.89) = 1054.85 J

HRxn = -Qrxn/n = -1054.85 / (5.6/123.88) =  -23334.7 J  

choose E

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