Calculate the enthalpy change in KJ for the following reaction 2AL(s) +2 Fe(s)- 2Fe (s)+Al2O3(s)?
2AL(s)+3/2O2(g)- Al2O3(s)
H=-1669.8KJ
2Fe(s) + 3/2 O2(g)- Fe2O3
H= -824.2KJ
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Answer:
I think you have made a mistake in typing the equation. The equation should be:
2Al + Fe2O3 ----> Al2O3 + 2Fe
{The aluminothermic process for extraction of iron}
According to Hess' law, the chemical equations can be added or subtracted as if they were algebraic equations. We need to express the above equation in the form of the 2 equations the data of which is provided.
Reversing the second equation, we have
Fe2O3 ----> 2Fe + 3/2 O2 {ΔH = +824.2 kJ}
Adding this to the first equation, we have
2Al + Fe2O3 +3/2 O2 ----> 2Fe + 3/2 O2 + Al2O3
Cancelling the commom O2,
2Al + Fe2O3 ----> 2Fe + Al2O3.
ΔH(reaction) = -1669.8+824.2 =-845.6 kJ
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