How much heat in kJ is evoleved when 5.00 grams of Aluminum reacts with 25.0 grams of Iron (III) Orxide?
Al (s) + Fe2O3 (s) --> Fe (s) + Al2O3 (s) +851.5 kJ
2007-10-26 07:20:45 · 2 answers · asked by kay 2 in Science & Mathematics ➔ Chemistry
3Al(s) + Fe2O3(s) ===> 3Fe(s) + Al2O3(s) -851kJ
Atomic weights: Al=27 Fe=55.8 O=16 Fe2O3=160
5.00gAl/ x 1molAl/27gAl = 0.185 mole Al
25gFe2O3 x 1molFe2O3/160gFe2O3 = 0.156 mole Fe2O3
0.156 moles Fe2O3 require 0.474 moles Al, and you haven't got that. So Al is the limiting reagent. It will run out first. Also, this is a highly exothermic reaction. So that should be -851kJ. Also, is that kJ/mole?
0.185molAl x -851kJ/1molAl = -157kJ
2007-10-26 07:34:02 · answer #1 · answered by steve_geo1 7 · 0⤊ 0⤋
5 g of Al = 5/27 = 0.185 g-atom of Al
25 g of Fe2O3 = 25/160 = 0.156 g-mole of Fe2O3
0.156 < 0.185
So Heat evolved = 0.156 * 851.5 kJ
= 133 kJ.
2007-10-26 07:29:13 · answer #2 · answered by Madhukar 7 · 0⤊ 0⤋