The reaction between Al and Fe 2 O 3 is a very exothermic reaction known as the

Question

The reaction between Al and Fe2O3 is a very exothermic reaction known as the thermite reaction. This reaction is so exothermic that under the right conditions it can lead to the formation of molten Fe instead of solid Fe. This reaction was originally used to weld together railroad ties in the early days of railroad construction. The balanced reaction appears below:

2 Al (s) + Fe2O3 (s) --------> 2 Fe (s) + Al2O3

How much energy (in kJ) is released when 3.17 kilograms of Al are reacted in the following manner? Include the correct sign for the energy change.

Explanation / Answer

HRxn = Hprod - Hreact = (2*0 + 1*-1675.7) - (2*0 + 1*-824.2) = -851.5 kJ/mol

so...

mol of Aluminium = mass/MW = (3.17*10^3)/26.981539 = 117.487 mol of Al

so..

expected heat -->

2 mol of Al --> -851.5

117.487 mol --> X

X = -117.487 /2*851.5

Q = -50020.09025 J

Q = -50.020 kJ

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