Calculate the standard enthalpy change for a reaction? : Fe2O3(s) + 2Al(s) = Al2O3(s) + 2Fe(s).

The standard enthalpies of formation of Fe2O3 and Al2O3 are
-822 and -1669 KJ mol-1 respectively. State whether the reaction is exothermic or
endothermic

1 Answer
anor277
Dec 4, 2017

We assess the reaction...

#Fe_2O_3(s) + 2Al(s) rarrAl_2O_3(s) + 2Fe(s)#

Explanation:

And always....#DeltaH_"rxn"^@=Sigma(DeltaH_"products"^@-DeltaH_"reactants"^@)#

And we note that BY DEFINITION, #DeltaH_"element"^@=0*kJ*mol^-1# FOR AN ELEMENT in its standard state under standard conditions, the which apply here.

And so we take the summation and observe the sign conventions,

#{(-1669)-(-822)}*kJ*mol^-1=-847*kJ*mol^-1#.

#DeltaH_"rxn"^@=-847*kJ*mol^-1#...and by #mol^-1# we mean PER MOLE of REACTION as written....

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